code: osa overhaul a sub- assembly - learning material.pdfremove the number one connecting rod cap...

Diesel Mechanic: Module OSA

- Mining Qualifications Authority - All rights reserved

Created : 01 February 2003

Revised : March 2015

Owner : Learnership Department

First Published : March 2003

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DIESEL MECHANIC

CODE: OSA

OVERHAUL A SUB-

ASSEMBLY







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INDEX

The following elements are contained in this learning guide:

TOPIC PAGE NUMBER

Index 2

Module Objective and Additional resources 4 - 5

HIAC 6 - 7

The Condition Report 8 - 12

Introduction 13

The Sub - Assembly 14 - 16

Dismantling of the sub-assembly 17

Disassemble the front end 17

Self Test 1 22

Disassemble pistons and connecting rods 23 - 27

Remove the main bearing caps 28 - 30

Remove the camshaft 30 - 32

Dismantling of piston assembly 33 -- 45

Self Test 2 46 - 47

Practise 48

Assessment of all parts 49 - 60

Self Test 3 61

Practice 62

Crankshaft construction 63 - 71

Self Test 4 72

Practice 73

Conrod assembly 74 - 80

Self Test 5 81

Practice 81

Oil pumps 82 - 89

Self Test 6 90







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INDEX CONTINUED…..TOPIC PAGE NUMBER

Practice 90

Checking relieve valve 91

Rotary oil pump driven by crankshaft 91 - 93

Self test 7 94

Practise 94

Assembling of sub-assembly 95 - 97

Practise 97

Replace the camshaft 98

Refit the crankshaft 99 - 103

Practise 104

Assembling piston assembly 105 - 109

Fit oil pump with oil pipe 109 - 110

Set valve timing 111 - 114

Inspection of timing gears 114

Inspection of timing chain 115

Inspection of timing belt 116 - 117

Self test 8 118 - 119

Practise 120







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OBJECTIVE What you must do 1. Dismantle, assess and assemble a sub-assembly. 2. Remove the ridges, glaze and high spots from the cylinder bores. 3. Set the valve timing. 4. Complete the condition report (see Page 3). What you will be given 1. An engine sub-assembly. 2. All the necessary tools and equipment. How well you must do it 1. There must not be any damage to the fasteners or parts. 2. There must not be any damage to equipment. 3. The ridges in the cylinder bores must be removed before removing the piston

assemblies. 4. The ring gaps must be staggered on the piston. 5. The glaze and high spots in the cylinders must be removed with a hone before re-

installing the pistons. 6. The pistons and connecting rods must be re-fitted to the same cylinders from which

they were removed. 7. The timing marks must correspond when No. 1 piston is at TDC on the power stroke. 8. All the parts must be clean and free of grit or grime. 9. All the parts must be smeared with oil before they are fitted. 10. All bolts must be lubricated and torqued to specifications. 11. All the measured sizes must be within the tolerance of + 0, 05 mm.







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12. All the technical data on the Condition Report must comply with the data given in the Workshop Manual.

13. The crankshaft must turn freely after installation. 14. The main bearing caps must be re-fitted to the main bearings from which they were

removed. 15. All the locking devices on the main bearing and connecting rod bearing caps must be

re-fitted. 16. The Condition Report must be completed. ADDITIONAL RESOURCES 1. Your Training Officer

2. Workshop Manual. 3. Audio-visual aids if available. 4. "Fundamentals of Service" by John Deere. Pages 2-23 to 2-64







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HAZARD IDENTIFICATION AND CONTROL (HIAC) FORM

OSA

OVRHAUL A SUB-ASSEMBLY

STEPS IN OPERATION /

PROCESS

POTENTIAL ACCIDENT /

INCIDENT

CONTROLS (BY

RESPONSIBLE PERSON)

1. Use hand tools. •Using damaged tools or wrong tools for the job can cause injury and damage to equipment.

•Always use the correct tool for the job. •Ensure tools are in good condition. Use tools correctly. •Wear appropriate PPE where necessary. • Always take good care of tools. Maintain, clean and store it properly.

2.Work on component •Working on component can cause injury due to pinching between tools and component.

•Make sure that tools are used in the proper way. •Always keep fingers clear from possible pinching areas







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3.Falling parts & tools •Improperly stored parts or tools can fall and cause injury or damage to parts or tools.

•Ensure that parts and tools are placed in such a way that they do not fall from work bench. •Place all parts or tools in such a way that they are unable to roll from the work bench.

NOTE: Before doing the practical work contained in this module, the learner must study the content of the above HIAC Form again and then sign the statement below: The above risks, which will be encountered in this module, are fully understood and will be controlled during the practical work. Signature of Learner:…………………………………… Signature of Training Officer:…………………………….. Date:………………………….







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OVERHAUL A SUB-ASSEMBLY ITEM / TASK: The Condition Report DESCRIPTION: 1. CYLINDER BLOCK

YES N0

a) The face of the cylinder block is flat

b) Deposits of scale are present in the water jackets

c) Studs and bolt threads are damaged

d) The cylinder block is cracked

e) The bearings are scored

f) Taper of cylinder liner bores

a) Taper of cylinder liner bores (Standard size)

Cylinder No

1

2

3

4

5

6

Taper

Allowable Taper

b) Ovality of cylinder liner bores

Cylinder No

1

2

3

4

5

6

Ovality

Allowable Ovality

c) Clearance on camshaft bushes

Bush No

1

2

3

4

5

6

Clearance

Allowable Clearance







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d) Main bearing to crankshaft clearance

Bearing No

1

2

3

4

5

6

Clearance

Allowable Clearance

e) Cam follower clearance

Follower No

1

2

3

4

5

6

Clearance

Allowable Clearance

2. PISTON ASSEMBLY

YES NO

a) Bearings are scored

b) Bearing cap bolts are stretched due to over torque

a) Piston and rod are misaligned

Piston No

1

2

3

4

5

6

Yes/No

b) Piston clearance

Piston No

1

2

3

4

5

6

Clearance

Allowable Clearance







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c) Bearing crushes on connecting rod bearings

Piston No

1

2

3

4

5

6

Crush

Recommended Crush

d) Bearing clearance (Oil clearance) on crankshaft

Piston No

1

2

3

4

5

6

Clearance

Allowable Clearance

e) Ring gap on compression rings

Piston No

1

2

3

4

5

6

Gap

Allowable Gap

f) Piston pin fit

Piston No

1

2

3

4

5

6

Pin is loose YES/NO

Bush is taper YES/NO

Bush is bell-mouthed YES/NO







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3. CRANKSHAFT ASSEMBLY

YES N0

a) The crankshaft is cracked

b) The oil ports are blocked

c) The crankshaft journals are scored

c)

End float Actual Allowable

e) Main bearing journal wear, and ovality.

Journal No

1

2

3

4

5

6

Wear- YES/NO

Ovality

Allowable ovality

Allowable wear

f) Connecting rod journal wear and ovality

Piston No

1

2

3

4

5

6

Wear- YES/NO

Ovality

Allowable ovality

Allowable wear







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4. LUBRICATION SYSTEM

YES N0

a) The oil strainer is blocked

b) Refer to your Workshop Manual for all the clearances to be checked on the pump

External Gear Pump

ACTUAL ALLOWABLE

a) End play on pump shaft

b) Clearance between gears and housing

c) Clearance between face of pump gears and body

d) Pump cover must be replaced YES NO

Rotor Pump

ACTUAL ALLOWABLE

a) Clearance between pump body and rotors (front)

b) Clearance between the outer rotor and the pump body

c) Clearance between the rotors

d) End play on pump shaft

YES NO

e) Pump cover must be replaced







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INTRODUCTION

Engine removal and disassembly procedures vary from vehicle to vehicle. However, there are general rules and methods that apply to all vehicles and small trucks. (Fig. 1)

Before engine removal, make sure all necessary parts are disconnected or removed.

It is sometimes necessary to remove the engine and transmission as a unit. Some front-wheel- drive vehicles that use a transaxle require that the two be removed as a unit.

Position a lifting fixture or chain so that it will raise the engine in a level manner.

As soon as you can, lower the engine to the ground or mount it on an engine stand.

Disassemble the engine and inspect each part for signs of trouble.

Teardown methods vary somewhat from engine to engine. However, general procedures are similar and apply to all engines.

After you have removed all the parts from the engine block and cylinder head, everything should be cleaned.

Different cleaning techniques are needed, depending on part construction and material type.

Fig. 1







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THE SUB - ASSEMBLY

The sub-assembly of a diesel engine consists of the following parts, which have to be assessed and replaced if necessary.

a) Cylinder block (Engine block)

The block is the main housing of the engine and supports the other main parts. (Fig. 2)

b) Cylinders (bores)

The cylinders are hollow tubes in which the piston works. They are cast into the cylinder block or made of liners or sleeves. (Fig. 2)

c) Piston

The piston and cylinder are mated parts, closely fitting so that the piston slides easily up and down in the cylinder. The piston is moved up and down by the force of combustion. (Fig. 3 on next page)

d) Connecting rods

The connecting rod is the link which transmits the motion of the piston to the crankshaft. (Fig. 3 on next page)

Fig. 2







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e) Crankshaft

The crankshaft has a section offset (Fig. 4) from the centre line of the shaft so that it "cranks" when the shaft is turned.

Fig. 3

Big end journal

Main journal

Fig. 4







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f) Camshaft

The camshaft rotating in the engine block opens the valves by cam action as described in Module OCA. (Fig. 5)

g) Timing drives

The timing drives link the crankshaft, camshaft and in some engine the injector pump together to ensure that the valves are opened and the fuel are injected into the cylinders at the right time. (Fig. 6)

Fig. 5

Fig. 6







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DISMANTLING OF THE SUB-ASSEMBLY The following major steps must be followed to dismantle the sub-assembly. For more details refer to your Workshop Manual.

Drain the oil from the sump.

Clean the engine on the inside and outside with a solvent

Remove the sump

Remove the oil pump ENGINE FRONT END DISASSEMBLY Engine front end disassembly is simple if a few basic rules and service manual instructions are followed.

Remove the water pump and any other parts bolted in front of the engine timing cover. If a timing belt is used, remove the bell cover.

Loosen the tensioner and slip off the belt (this would have to be done before cylinder head removal). (Fig. 7)

Do not attempt to rotate the crankshaft of an overhead cam engine with the timing belt off (cylinder head still in place).

The pistons could slide up and bend the valves.

Fig. 7







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A wheel puller is normally needed to remove the harmonic balancer or damper.

The balancer is commonly press-fit onto the crankshaft. (Fig. 8) shows how to use a wheel puller.

NB: Hold the flywheel ring gear stationary to prevent the crankshaft from turning when removing the crankshaft pulley.

Unbolt and remove the timing chain or gear cover.

If prying is necessary, do it lightly while tapping with a rubber hammer.

Do not bend or scar mating surfaces. (Fig.9)

The cover may be reluctant to come free, either because it is glued in place with sealant or because of a tight fit on locating pins.

But before doing anything drastic by way of pry bars, make absolutely certain that all fasteners are removed. (Fig.9)

Front covers are often secured at the bottom by pan bolts and may also be bolted to the underside of the head, Japanese fashion.

Other less obvious fasteners, such as water-pump thru-bolts and the “back-of-the-oil-pump” bolt. (Fig.9)

Remove the oil slinger and timing mechanism.

Usually, the timing gears or sprockets will slide off after light taps with a brass hammer. If not, use a wheel puller.

Fig. 8







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If the oil pump or other components are mounted in the front cover, refer to a service manual for directions.

Different Front End types on engines

There are three basic types of camshaft drives :( Front End types) These drives are all housed in the Front End Assembly

1. Camshaft driven by Timing Gears 2. Camshaft driven timing chain and sprockets 3. Camshaft driven timing belt and sprockets.

NB: Take note of the different front end construction and assemblies.

Once the cover is removed, rotate the crankshaft to TDC on No. 1 piston and make careful note of the timing marks. This is the last time you will see these marks in their factory-set alignment.

Fig. 9







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Camshaft driven by Timing Gears (Fig.10) Camshaft driven by a timing chain and sprockets. (Fig.11)

Fig. 10

Fig. 11







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Camshaft driven by Timing belt and sprockets. (Fig.12)

DO THE SELF-TEST ON THE NEXT PAGE BEFORE CONTINUING WITH THE REST OF THE MODULE

Fig. 12







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SELF TEST 1 WITHOUT REFERRING TO YOUR NOTES, ANSWER THE FOLLOWING QUESTIONS:

1. Name 7 basic components of Sub Assembly and state their function __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________

2. Name 3 different Front End types on engines.

__________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________

Call your Training Officer to check your work and to sign you off when it is correct, then go on to the next section.

LEARNER

TRAINING OFFICER

Date:

Date:

Signed:

Signed:







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DISASSEMBLE PISTONS AND CONNECTING RODS

Before removing the piston assembly, examine the bores for ridges. The top ring on the piston is usually poorly lubricated because it is exposed to the extremely hot, high pressure combustion gases which blow or boil the oil off it.

Therefore cylinder bore wear is greatest at the upper end of the top ring travel. (Fig.13)

Completely remove the ridge at the top of each cylinder with a ridge reaming tool (see illustration). (Fig.14)

Fig. 13

Fig. 14







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Follow the manufacturer’s instructions provided with the tool. (Fig.15)

Failure to remove the ridge before attempting to remove the piston/connecting rod assemblies may result in piston breakage

After the cylinder ridges have been removed, turn the engine upside-down so the crankshaft is facing up.

Before the connecting rods are removed, check the endplay with a feeler gauge (Fig.16 on next page) or a dial gauge (Fig.17 on next page).

Slide them between each connecting rod and the crankshaft throw until the play is removed.

The endplay is equal to the thickness of the feeler gauge(s).

If the endplay exceeds the service limit (about 0.08mm in on most models), new connecting rods will be required.

Repeat the procedure for the remaining connecting rods.

Fig. 15







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NB: Before removing the connecting rod caps, note whether the rods and caps are numbered to indicate the cylinder to which they are fitted. (Fig. 18)

Fig. 16

Fig. 17

Fig. 18







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NB: Also note on which side of the engine the numbers are placed. On In-Line engine, the numbers are usually on the camshaft side of the engine.

If the rods are not numbered, identify them with punch marks or paint.

Loosen each of the connecting rod cap nuts 1/2-turn at a time until they can be removed by hand.

Remove the number one connecting rod cap and bearing insert. Don’t drop the bearing insert out of the cap. (Fig.19)

Push the connecting rod/piston assembly out through the top of the engine.

Use a wooden hammer handle to push on the upper bearing insert in the connecting rod.

If resistance is felt, double-check to make sure that the entire ridge was removed from the cylinder.

NB: Check pistons for markings of each piston conecting rod and big end bearing cub and piston arrow pointing to front of engine. (Fig.20 and Fig.21on next page)

Fig. 19







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Remove flywheel from rear of engine(Fig.22)

Fig. 21

Fig. 20

Sump

Fly wheel

Fig. 22







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REMOVE THE MAIN BEARING CAPS Before removing the main bearing caps, note whether the caps are marked and note on which side of the engine these marks are placed. (Fig.23)

NB: Use centre punch or number stamping dies to mark main bearing caps from front to rear of engine and on engine front side of engine if not marked. (Fig.24)

Main bearing

caps

Big end caps

Oil seal

Fig. 23







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Loosen each of the main bearing cap bolts a ¼ turn at a time, until they can be removed by hand(Fig.25 )

Gently tap the caps with a soft-face hammer and then separate them from the engine block.

If necessary, use the bolts as levers to remove the caps.

Carefully lift the crankshaft out of the engine. It’s a good idea to have an assistant available, since the crank shaft is quite heavy. (Fig.26)

Remove the crankshaft from the cylinder block. Be careful not to scratch or nick any of the journals of the crankshaft.

Main bearing cup bolts




Fig. 25

Crank shaft Side stop thrust washers

Fig. 26







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Remove the main bearing shells from the cylinder block. (Fig.27)

REMOVE THE CAMSHAFT (Fig.28) NB: Before removing the camshaft it is advisable to lay the engine on its side to prevent the camshaft followers from falling out.

Main bearing shells

Side stop thrust washers

Fig. 27

Cham

shaft Bolts

Fig. 28







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Remove the camshaft followers A cross-sectional view of a stud type cam follower (Fig.29)

Remove the cam followers; mark them so that they can be re-installed in the same bores from which they were removed (Fig.30)

Clean all the parts thoroughly in a solvent. Hydraulic lifters (cam followers) A device that eliminates the need for mechanical clearance in the valve train of internal combustion engines. Clearance is normally required to prevent the valve's being held open and destroyed as the valve train undergoes thermal expansion. However, clearance requires frequent adjustment and is responsible for much operating noise.

Fig. 29

Fig. 30







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The hydraulic lifter is a telescoping compression strut in the linkage between cam and valve, consisting of a piston and cylinder (see illustration). When no opening load exists, a weak spring moves the piston, extending the strut and eliminating any clearance. This action sucks oil into the cylinder past a check valve. The trapped oil transmits the valve-opening forces with little deflection. A slight leakage of oil during lift shortens the strut, assuring valve closure. The leakage oil is replaced as the spring again extends the strut at no load. Positions of the hydraulic valve lifter, with engine valve (a) open and (b) closed. (Fig.31)

Fig. 31







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DISMANTLING OF PISTON ASSEMBLY All the different parts of a piston assembly are shown in (Fig.32) A small amount of clearance between the piston and the cylinder bore exists to allow an oil film to coat both surfaces in order to reduce wear. The head of the piston has more clearance than the skirt because it operates at a higher temperature and therefore expands more. The main parts of a piston are: as shown in (Fig.33) a) Head or crown b) Skirt c) Ring Grooves Piston dimentions shown in (Fig.33)

Fig. 32

Fig. 33







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The skirt of the piston normally has an elliptical shape so that it will fit the cylinder during operation when it is hot. (Fig.34) The narrow part is across the piston pin holes (A), where the metal is thickest, while the wider part is where the metal is thinnest (B) (Fig.35)

NB: When measuring a piston, the dimension must always be taken across (A) and (B).

Measurements AA – BB = Ovality of Piston (Fig.35)

Measurement CC- DD = Taperness of piston (Fig.35)

Check the piston pin for out-of-roundness or looseness.

Clamp the pin in a pin vice and rotate the rod back and forth on the pin several times.

Fig. 34

Fig. 35







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Then remove the rod and examine the shiny contact spots.

A good pin fit will show contact over the entire surface of the bushing Taperness of pistons

Piston No

1

2

3

4

5

6

Measurement CC

Measurement DD

Taper

Ovality of Pistons

Piston No

1

2

3

4

5

6

Measurement AA

Measurement BB

Ovality

Types of rings (Fig. 36 on next page)

compression rings

oil rings Compression rings

compression ring no 1 (top compression ring)

compression ring no 2 (bottom compression ring)







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Major types of compression rings Example of the major types of compression rings (ford) (Fig. 37)

All the rings when fitted into the cylinder block must have a gap which is wide enough to prevent the ends from touching when the ring heats up and expands during operation.

Fig. 36

Fig.37







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The ring gap is the small space between the ends of the ring when it is installed on the piston and the piston is in the cylinder.

The three common ring joints are shown in (Fig. 38)

Oil rings An oil ring must wipe of excess oil of the cylinder wall. If oil entered the combustion chamber, the engine would emit blue smoke. (Fig. 39)

Fig. 38

Fig. 39







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Types of oil rings: (Fig. 40)

A- three piece oil ring

B- one piece oil ring with expander

Remove the piston rings using a ring expander (Fig 41)

Fig. 40

Fig. 41







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Remove the piston pin. The procedure in removing piston pins depends on whether the pin floats, or is locked to the piston or to the rod (Fig. 42)

Remove the fasteners.

Place the piston in boiling water to allow it to expand and push the pin out by hand.

NB: Before removing the piston pins, the pistons should be numbered with a centre punch or paint. One mark for No. 1 piston, two marks for No. 2 piston, etc.

Put these marks on the same side as the rod number and be careful to re-assemble the rods and pistons accordingly. (Fig 43)

All free-floating piston pins is held in place by snap rings.

Fig. 42

Fig. 43







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The pin should slide in and out of the piston and rod with finger pressure or with light taps with brass drift and a hammer. (Fig 44)

A press-fit piston must be forced out with a press.

Clean all the parts with a solvent.

Remove all the carbon in the ring grooves with a special tool (Fig 45).

A broken piston ring with a sharp, square end makes a good tool for cleaning ring grooves (Fig 46)

Fig. 44

Fig. 45







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Check the ring grooves for wear.

Pistons should be replaced whenever the ring grooves are worn excessively.

Refer to the Workshop Manual for wear limits.

Check the pistons grooves at several points because the grooves wear unevenly. (Fig 47)

Fig. 46

Fig. 47







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Check the ring groove wear by installing a new ring in the groove. (Fig 48)

Then insert a feeler gauge between the upper surface of the new ring and the land to check the clearance (Fig. 49).

Fig. 49

Fig. 48







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Measure ring to ring groove clearance (Fig. 50).

The compression ring must prevent combustion pressure from leaking between the piston and the cylinder wall.

Pressure actually helps push the ring against the cylinder to aid sealing. (Fig. 51)

To measure piston ring end gap clearance, install the ring in cylinder and push it to the bottom of ring travel with the head of the piston.

Fig. 50

Fig. 51







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Use a feeler gauge to measure the gap. (Fig. 53)

Piston pin clearance Piston Pin Diameter (Fig. 54 on next page)

Use a micro meter to measure the piston pin diameter at several points.

If the measured value is less than the specified limit, the piston pin must be replaced.

Fig. 52

Fig. 53







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Piston Pin and Piston hole Clearance(Fig. 55)

Use telescopic gauge to measure the hole (in the piston).

Subtract the piston pin size from the hole size.

This will be the piston pin clearance in mm

GO ON TO THE NEXT PAGE TO DO THE SELF TEST.

Fig. 54

Fig. 55







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SELF TEST 2 Without referring to your notes, label the drawing.

1._______________________ 2._______________________ 3._______________________ 4._______________________ 5._______________________ 6._______________________ 7._______________________ 8._______________________ 9._______________________ 10.______________________ 11.______________________

2. Name the major types of compression rings. _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

1 5

6

7

8

9

2

3

4

11

10







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3. Name the Types of oil ring.

________________________________________________________________________________________________________________________________________ ____________________________________________________________________ ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

4. Explain by means of sketches the following measurements. a) Piston ovality

b) Piston taperness c) Ring groove clearance. d) Ring gap clearance in cylinder







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PRACTICE Go to the sub-assembly of the diesel engine and dismantle it. Call your Training Officer to check your work. When you have achieved the required standards, ask him to sign below before you go on to the next section.

LEARNER

TRAINING OFFICER

Date:

Date:

Signed:

Signed:







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ASSESSMENT OF ALL THE PARTS a) Cylinder block

Scrape all gasket material from the block and clean it inside and outside. (Fig. 56)

Apply air pressure to all the oil galleries to clean out any dirt or grime (using goggles). (Fig. 57)

Check the studs in the cylinder block for loose-ness. Also check for any damage on the threads.

Check the threaded holes. Use a tap to clean the threads.

Carefully remove any nicks or burrs from the machined surfaces with a smooth file.

Check the cylinder block for flatness with an accurate straight edge and a feeler gauge (Fig. 58 on next page).

Fig. 56







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NB: If the cylinder block is warped, it must be re-surfaced or replaced.

Check the cylinder block for cracks or leaks by using the water-and-air pressure method as described in Module OCA.

Check the cylinders for taper and out-of-round-ness by following the procedures described below. (Fig. 59)

Fig. 58

Fig. 59







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Measure the bore parallel to the crankshaft at the top end of the ring travel zone (Fig. 60)

Measure the bore parallel to the crankshaft at the bottom end of the ring travel zone.

Measure the bore at right angles to the crankshaft at the top end of the ring travel zone. (Fig. 61)

Fig. 60

Fig. 61







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Measure the bore at right angles to the crank-shaft at the bottom end of the ring travel zone.

Subtract the measurements (1) and (3) from each other to find the out-of-round wear at the top end of the bore.

Subtract the measurements (2) and (4) from each other to find the out-of-round wear at the bottom end of the bore.

Compare all four measurements to find out whether or not the bore has worn tapered.

To measure the bore diameters use a cylinder dial, an inside micro meter, or a telescopic gauge and outside micro meter. (Fig. 62 and Fig. 63)

Fig. 62

Fig. 63







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Taperness of cylinder liner bores

Cylinder No

1

2

3

4

5

6

Measurement AA

Measurement BB

Measurement CC

Taper

Ovality of cylinder liner bores

Cylinder No

1

2

3

4

5

6

Measurement AA

Measurement BB

Measurement CC

Ovality

There are two basic types of cylinders: Cast-in-Block (Fig. 64) Liners or Sleeves

Fig. 64







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Cast-in-Block (Fig. 64)

The cylinders are cast into the cylinder block so that the cylinders and block form a single unit. When these types of cylinders have reached their wear limits they must be re-bored.

Liners or Sleeves (Fig. 65)

There are two types of liners, dry liners and wet liners. The dry liners are sleeves which fit inside an already completed cylinder. This liner is simply a wearing surface for the piston. They are not exposed to the engine coolant so they are called "dry". Wet liners form not only the cylinder wall, but also the out inside of the water jacket (Fig. 65)

NB: The amount of cylinder taper and out-of-round-ness that can be allowed without re-

boring or re-sleeving the engine depends on the design and the type of service for which the engine is used. For the exact wear limits refer to your Workshop Manual.

Check if excessive deposits of scale are present in the water jackets.

Fig. 65







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Check the piston to sleeve clearance by:

Measuring the cylinder diameter at right angles to the crankshaft at the least worn area of the cylinder.

Measuring the diameter of the piston at right angles to the piston pin bore (Fig. 42)

The difference between these two measurements is the piston clearance. a) Piston to sleeve clearance

Piston No

1

2

3

4

5

6

Sleeve Max Dia.

Piston Min Dia.

Clearance

Assessing the Camshaft

After the camshaft has been removed from the engine, cleaned with solvent and dried, inspect the bearing journals for uneven wear, pits and galling.

If the journals are damaged, the bearing inserts in the block are probably damaged as well.

Replace both the camshaft and bearings if this is the case.

Normally, if the journals are not damaged and have a smooth finish, they are OK.

Measure the camshaft bearing journals with a micrometer (see illustration).

Compare the measurements with the specifications in the Repair Manual for your particular vehicle.

If they’re less than specified, the camshaft should be replaced with a new one.

Subtract the bearing journal diameters from the corresponding bearing inside diameter measurements to obtain the oil clearance.

Generally, the oil clearance not exceed about 0.05mm







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Check the camshaft lobes for heat discoloration, score marks, chipped areas and pitting.

If any of these conditions are present on any lobe, replace the camshaft To measure cam lift (Fig. 66)

Measure it as follows.

Take the measurement where the cam diameter is largest = Measurement A

Take the measurement where the cam diameter is smallest = Measurement B

Cam lift (lobe) = Measurement A - Measurement B

Ex. 38mm – 30mm = 8mm lift height

Camshaft alignment (Fig. 67 on next page)

Mount the camshaft in two V-bocks.

Position the dial indicator on the centre journal, turn the cam and read the dial indicator.

If the camshaft is not straight, replace it.

Fig. 66







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Check the camshaft bush clearance by:

Measuring the camshaft journals with an outside micrometer (Fig. 68)

Measuring the camshaft bearings with an inside micrometer or telescopic gauge and outside micrometer (Fig. 69)

(Fig. 73)

Fig. 67

Fig. 68

Fig. 69







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Subtracting (1) from (2) and comparing the results with the specifications in the Workshop Manual.

Check the camshaft bushes for score marks or any damage.

Check the cam follower clearance by:

Measuring the outside diameter of the cam follower body(Fig. 70)

Measuring the inside diameter of the cylinder block cam follower bore (Fig. 71)

.

Rocker arm

Cam follower

Fig. 70

Fig. 71







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Subtracting (2) from (1) and comparing the results with the specifications in the Workshop Manual.

Visually inspect pushrod and rocker arm contact surfaces for pitting, cracking and any other abnormal conditions. (Fig. 72)

Wear abnormalties

1. Normal contact

2. Cracking

Fig. 72







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3. Pitting

4. Uneven contact

5. One sided contact








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SELF TEST 3 Without referring to your notes answer the following questions.

1. Name 2 types of cylinder liners. _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ __________________________________________________________________________________________________________________________________________

2. Explain by means of sketches the following measurement’s:

a) Cylinder block flatness

b) Cylinder Taperness

c) Cylinder Ovality

d) Cam lift (lobe) height







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PRACTICE You should practice all the foregoing steps in assessing a cylinder block and fill in all the data applicable to the cylinder block on the Condition Report. When you have completed the assessment to the standards required, ask your Training Officer to go on to the next section.

LEARNER

TRAINING OFFICER

Date:

Date:

Signed:

Signed:







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Crankshaft Construction Engine crankshafts are usually made of cast iron or cast from a heat treated steel alloy for extra strength or forged steel. Forged steel crankshafts are needed for heavy-duty applications, such as turbocharged or diesel engines. A steel crankshaft is stiffer and stronger than a cast iron crankshaft. It will withstand greater forces without flexing, twisting, or breaking. The crankshaft is drop forged or it is usually made in one piece (Fig 73)

Check if any of the oil passages are blocked by applying air pressure.

Oil holes are drilled through the crankshaft journals to match the holes leading in from the block. (Fig 74)

Fig. 73

Fig. 74







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This oils the main and connecting rod bearings as shown, while the excess oil sprays out to help lubricate the pistons and cylinders (Fig 75)

Inspect the Crankshaft oil seal surfaces for nicks, sharp edges or burrs that could cause damage to the oil seal, or cause premature failure(Fig 76)

Fig. 75

Fig. 76


Revised : November 2013



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If the crankshaft has passed all other inspections and measurements, check the journal run –out by using a dial indicator.

Support the crankshaft in Two V-blocks and check the run-out. (Fig 77)

(Fig 82)

Compare to specifications.

If the crankshaft fails any inspection for wear or damage, it must be re-ground or replaced

Check if any of the journals are scored (Fig 78) or badly ridged in the oil groove in the bearing shell (Fig 79 on next page)

Fig. 77

Fig. 78





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Main and connecting rod journals of most crank-shafts are induction hardened.

They are ground and polished to the exact bearing s

Check if the crankshaft is not cracked (Fig. 80).

Fig. 79

Fig. 80





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Measure the Main and Big end bearing journals for ovality and wear (Fig. 81)

Measure the journal at position A and B across the Y-Y axis.

Subtract the two dimensions taken in (1) from each other to determine if it is worn taper.

Measure the journal at position A and B across the X-X axis (Fig. 36 above).

Subtract dimensions "A" at the Y-Y axis and the dimension "A" at the X-X axis from each other and do the same with the dimensions "B" at the Y-Y and X-X axes to determine the ovality of the journal.

Take the smallest size on the journal and compare it with the wear limits specified in the Workshop Manual.

Main bearing journal Taperness and ovality

Journal No

1

2

3

4

5

6

Measurement AA

Measurement BB

Ovality

Taperness

Fig. 81





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Connecting rod journal Taperness and ovality

Piston No

1

2

3

4

5

6

Measurement CC

Measurement DD

Ovality

Taperness

Check the main bearing clearance by using a "plastic gage".

Check if the main bearing inserts are not scored or damaged.

Replace all the main bearing inserts in the cylinder block.

Make sure that all the locking tangs are properly fitted in the grooves (Fig. 82)

Place the crankshaft in the cylinder block. (Fig. 83) NB: Do not lubricate the bearings and do not turn the shaft.

Bolts

Big end bearings

Thrust washer Fig. 82





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Replace the main bearing inserts in the main bearing caps.

Place a piece of "plastic gage" the full length of the bearing insert about 6 mm off centre (Fig. 84)

Crank shaft Thrust washer

Thrust washer

Fig. 83

Fig. 84





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Install the bearing cap and tighten the bolts to the specified torque. (Fig. 85)

Remove the bearing cap.

The flattened Plastic gage will be found adhering either to the bearing insert or the crankshaft.

Compare the width of the flattened Plastic gage at its widest point with the graduations on the envelope (Fig. 86)

Fig. 85

Fig. 86





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The number within the matching graduation on the envelope indicates the total clearance.

Main bearing oil clearance on crankshaft

Journal No

1

2

3

4

5

Clearance

Follow the exact same procedure to determine the oil clearance on the Big End journals

Big End bearing oil clearance on crankshaft

Journal No

1

2

3

4

5

6

Clearance


Fig. 87





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SELF TEST 4

1. Without referring to your notes explain by means of sketches the following measurements.

a) Crankshaft Tapernes

b) Crankshat Ovality

GO ON TO THE NEXT PAGE FOR THE PRACTICE.





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PRACTICE You should practice all the foregoing steps in assessing a crankshaft and fill in all the data applicable to the crankshaft on the Condition Report. When you have completed the assessment to the standards required, ask your Training Officer to sign you off and go on to the next section.

LEARNER

Training Officer

Date:

Date:

Signed:

Signed:





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ASSESSES THE CONROD ASSEMBLY

Check the bore of the piston pin bushing for taper or bell mouthing (Fig. 88).

Insert the pin from each end of the bushing. If it is free on one end, but tight on the opposite end the pin hole is tapered.

If it enters easily from either end, but becomes tight in the centre, the hole is bell mouthed

Inspect piston pin oil clearance

Using a calliper or telescopic gauge, measure the inside diameter of the connecting rod bushing. (Fig. 89)

Using a micro meter, measure the piston pin(Fig. 90)

Fig. 88

Fig. 89

Fig. 90





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If any problem is observed due to clearances being out of specifications, the small –end bush must be replaced

Align the oil holes of a new bushing and the connecting rod. (Fig. 91)

Using SST and a press, press in the bushing. SST(Fig. 92)

Using a pin hole grinder, hone the bushing to obtain the standard specified clearance (see item C above) between the bushing and piston. (Fig. 93)

Check the piston pin fit at normal room temperature.

Coat the piston pin with engine oil, and push it into the connecting rod with your thumb.

Fig. 91

Fig. 92

Fig. 93

Fig. 94





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Check the connecting rod alignment.

The rod should be checked for bend and twist. If the rod is twisted it will increase the wear on the piston pin, rod bearings and piston.

If the rod is bent, the piston pin will not be parallel with the crankpin. These cocks the rod bearing on the crankpin, causing extra wear where the bearing is pinched as shown by the arrows in (Fig. 96)

There are a number of alignment tools in use including the one shown in (Fig. 97).

Ask your Instructor for a demonstration on how to use the alignment tool in your Training Centre.

Fig. 95

Fig. 96





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Use the connecting rod aligner to measure the distortion and parallelism between the connecting rod big-end hole and the connecting rod small-end hole.

If either the measured distortion or parallelism exceeds the specified limit, the connecting rod must be replaced.

Check for bend. (Fig. 98)

Maximum bend: 0.03 mm (0.0012 in.) per 100 mm (3.94 in.)

If the bend is greater than the maximum, replace the connecting rod sub-assembly.

Fig. 97

Fig. 98





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Check if rod is twisted. (Fig.99)

Maximum twist: 0.15 mm (0.0059 in.) per 100 mm (3.94 in.)

If the twist is greater than the maximum, replace the connecting rod sub-assembly.

Check the bearing crush/nip/draw.

The halves of the thin shelves should project slightly above the flat face of the cap. (Fig. 100)

Fig. 99

Fig. 100





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The purpose of the projection is to compress the bearing into the bore to seat the

outside of the shell lightly against the cap.

Intimate contact is necessary not only to conduct heat away from the bearing, but also to provide a firm support for the heavy loads imposed on the bearing.

To check the crush, the following steps must be followed:

Fit the bearing shells to the connecting rod and tighten the bolts to torque specification.

Release the tension on one of the bolts.

Measure the gap between the rod and cap with a feeler gauge (Fig.101)

NB: General specifications: For small engines 0, 01 - 0,015 mm Large engines 0,015 - 0, 02 mm

Fig. 101





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Using a Vernier calliper, measure the minimum diameter of the elongated thread at the measuring point. (Fig.102)

Example:

Standard diameter: 13.500 to 14.000 mm (0.5315 to 0.5512 in.) Minimum diameter: 12.60 mm (0.4961 in.)

If the diameter is less than the minimum, replace the bolt.


Fig. 102





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SELF TEST 5 Without referring to your notes, answer the following questions.

1. Explain by means of sketches the following measurements:

a) Connecting rod bearing crush

PRACTICE You should practice all the foregoing steps assesses the conrod assembly and fill in all the data applicable to the assesses the conrod assembly on the Condition Report. When you have completed the assessment to the standards required, ask your Training Officer to go on to the next section.

LEARNER

TRAINING OFFICER

Date:

Date:

Signed:

Signed:





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Oil pumps External gear pump

It consists of two meshed spur gears enclosed in housing. There is very little clearance between the gear teeth and housing. One gear is attached to a shaft which is driven through suitable gears from the camshaft or crankshaft of the engine. The other gear is free to revolve on its own bearing. When the pump is in action, the oil is driven between the gear teeth from the inlet side, carried around between the gears and pump housing, and forced out the outlet sidle. The pressure quantities of the oil supplied by the pump depend upon the speed of the gears. An exploded view of a typical gear oil pump is shown in (Fig.103)

Fig. 103





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The following steps must be followed in assessing an external gear oil pump.

Dismantle the pump.

Clean all parts in a solvent.

Place a straight edge across the cover (Fig. 104) and try to insert a 0, 02 mm feeler gauge between the cover and straight edge. If the feeler can be inserted or if the cover is scratched or grooved, it must be replaced or refaced on a surface grinder.

Check the end play on the pump shaft by inserting a feeler between the gear and housing (Fig. 105).

Fig. 104

Fig. 105





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Check the clearance between the pump gears and housing (Fig. 106).

(Fig. 110)

Check the clearance between the face of the gears and the pump body with a straight edge and feeler gauge (Fig. 107).

Checking backlash of oil pump(Fig. 108)

New: 0.05 mm Wear limit: 0.20 mm.

Fig. 106

Fig. 107

Fig. 108







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Check the relief valve. The output of any positive displacement type pump such as those mentioned above, is

normally much more than is required in the oil system of the engine. An oil pressure relief valve is therefore used to by-pass the excess oil back into the oil

pan when the pressure exceeds the rated capacity of the pump. (Fig. 109)

Whenever an oil pump is removed for cleaning or repairs, the relief valve should be taken apart and cleaned. (Fig. 110)

This must not be overlooked because if the valve is held open with sludge or carbon, it will

not seat properly and will therefore allow oil to leak through it before the pressure reaches the proper maximum.

Fig. 109

Fig. 110







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NB: Where the relief valve is not built as part of the oil pump, it is connected in the oil

line.

Compare all the clearances with the specification in the Workshop Manual.

Assemble the oil pump. When assembling the pump, dip the gears in engine oil to provide for initial lubrication and priming.

Rotor Pumps

An engine oil pump in which an internal rotor, e.g., with four external lobes, is used to drive an eccentric external gear, e.g., with five internal lobe-spaces; operates in a similar way to Gear pumps, but has higher pump capacity, and is quieter and more expensive

In operation, the inner rotor is driven inside the rotor ring. The inner rotor has one less lobe than the ring so that only one lobe is engaged with the outer ring at any one time. This allows the other lobes to slide over the outer lobes, making a seat to prevent back-up of oil.

As the lobes slide up and over the lobes on the outer ring, oil is drawn in. As the lobes fall into the ring cavities, oil is squeezed out.

An exploded view of a typical rotor pump is shown in (Fig. 111).

Fig. 111







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The following steps must be followed in assessing a rotor pump.

Dismantle the pump.

Clean all parts in a solvent.

Place a straight edge across the cover (Fig. 112) and try to insert a 0, 02 mm feeler gauge between the cover and straight edge. If the feeler can be inserted or if the cover is scratched or grooved, it must be replaced or refaced on a surface grinder.

Check the clearance between the pump body and the rotors (Fig. 113).

Fig. 112

Fig. 113







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Check the clearance between outer rotor and the pump body (Fig. 114).

Check the clearance between outer rotor and inner rotor (Fig. 115).

Fig. 114

Fig. 115







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Check the end play of the pump shaft by inserting a feeler between the gear and housing (Fig. 116).


Fig. 116







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Self Test 6

Without referring to your notes, answer the following questions: 1. Name the different measurements to be taken on external gear pumps and rotor oil

pumps. __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________

PRACTICE You should practice all the foregoing steps in assessing oil pump and fill in all the data applicable to the oil pump on the Condition Report. When you have completed the assessment to the standards required, ask your Training Officer to go on to the next section.

LEARNER

TRAINING OFFICER

Date:

Date:

Signed:

Signed:







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Check the relief valve. Check the relief valve. The output of any positive displacement type pump such as

those mentioned above, is normally much more than is required in the oil system of the engine.

An oil pressure relief valve is therefore used to by-pass the excess oil back into the oil pan when the pressure exceeds the rated capacity of the pump.

Whenever an oil pump is removed for cleaning or repairs, the relief valve should be taken apart and cleaned. This must not be overlooked because if the valve is held open with sludge or carbon, it will not seat properly and will therefore allow oil to leak through it before

the pressure reaches the proper maximum. (Fig. 117)

Compare all the clearances with the specifications in the Workshop Manual.

Assemble the pump. When assembling the pump, dip the rotors in engine oil to provide for initial lubrication and priming.

Checking for wear on a Rotary oil Pump (later version Fig. 118)

Fig. 117

Fig. 118







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Exploded view shows parts of a Rotary oil pump that mounts on the front of the engine. (Fig. 118)

Measure Outer Rotor thickness. (Fig. 119)

Measure inner Rotor thickness. (Fig. 120)

Measure radial clearance between the inner rotor lobe and the outer rotor.(Fig. 121)

Fig. 119

Fig. 120

Fig. 121







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Measure the housing-to-rotor axial clearance.

Lay a straightedge over the rotors and see what size feeler gauge fits under the straightedge. (Fig. 122)

Measure radial clearance between the outer rotor and the oil pump housing.(Fig. 123)

a) Replace parts if your measurement is larger than specifications.


Fig. 122

Fig. 123







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SELF TEST 7 Without referring to your notes, answer the following questions:

1. Name the different measurments to be taken on a Rotor oil pump(crankshaft driven). _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

PRACTICE You should practice all the foregoing steps in assessing a gear and rotor pump and fill in all the data applicable to these pumps on the Condition Report. Ask your Training Officer to check your work and to sign you off when it is correct.

LEARNER

TRAINING OFFICER

Date:

Date:

Signed:

Signed:







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ASSEMBLING OF THE SUB-ASSEMBLY a) Honing the cylinder bores The glazing on the cylinder walls caused by the old rings, must be removed because too smooth a finish can retard the new piston ring seating. A flexible hone as shown in (Fig. 124) can be used to remove high spots - up to 0, 07 mm and to deglaze the cylinder walls.

The hone is rotated using an electric drill.

The stones and guides are pressed against the bore by both spring tension and centrifugal force. (Fig. 125)

Fig. 124

Fig. 125







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Insert the hone in the cylinder and start the drill (Fig. 126)

Move the hone up and down at the rate of about 30 times per minute. Allow the hone to protrude slightly at top and bottom.

After 20 or 30 strokes, examine the bore and repeat if necessary, until all the high spots have been removed. NB: The stones must be kept clean. If dirty or gummed, clean them with a wire brush

and kerosene.

After the high spots have been removed, the bore must be deglazed by rapidly moving the hone up and down - fast enough so that the scratches the hone makes on the bore surface are at an angle of about 45 degrees. (Fig. 127)

Fig. 126

Fig. 127







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When honing a cylinder, try to produce a 50* - 60* crosshatch pattern. Moving the drill up and down faster or slower alters the angle. (Fig. 131)

Wash the cylinder block thoroughly to remove all traces of grit after honing.

PRACTICE

Practise honing all the cylinder bores until the high spots have been removed and walls of the cylinders are deglazed as described before. Ask your Training Officer to check your work and if you have achieved the required standards ask him go on to the next section.

Ask your Training Officer to check your work and to sign you off when it is correct.

LEARNER

TRAINING OFFICER

Date:

Date:

Signed:

Signed:







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Main engine component’s (Fig. 128)

Use compressed air to thorougly clean the inside and outside surfaces of the cylinder block, the oil ports and water the jackets. Replace the camshaft

Apply a film of clean engine oil in the cam follower bores and on the cam follower bodies.

Refit the cam followers in the same bores from which they were removed. (Fig. 129)

Fig. 128

Fig. 129







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Coat the cam shaft journals and the bushes with clean engine oil

Refit the camshaft (Fig. 130)

NB: take care not to damage the camshaft bearings

NB. Refer to your workshop for more detail. c) Refit the crankshaft

Ensure bearing caps and cylinder block is thoroughly clean.

Install the bearing inserts in the cylinder block and the bearing caps. (Fig. 131)

Ensure oil holes of bearings and block are aligned. (Fig. 131)

Ensure that the locking tabs line up with the grooves in the bearing caps and the cylinder block. (Fig. 131)

Fig. 130

Fig. 131







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Apply a few drops of clean engine oil to the bearings and spread it over the bearing surface.

Carefully position the crankshaft on the bearings. (Fig. 132)

Apply an ample coat of engine oil to the thrust bearings before installation.

Install the thrust bearings to the crankshaft centre journal with the oil grooves facing to the sliding faces. (Fig. 133)

Apply a few drops of clean engine oil to the bearings in main bearing cups and spread it over the bearing surface.

Fig. 132

Fig. 133







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Install the remaining bearing halves and caps, making sure that the caps are installed at the mains from which they were removed by referring to the Identification marks made during removal.(Fig. 134)

(Fig. 135) illustrates a typical main bearing with thrust bearing. The ends of the bearing inserts are flanged and coated with a bearing metal. The adjacent crankshaft faces, course, are ground smoothly the same as the journal itself.

Fig. 134

Fig. 135







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Loosely install the bolts in the bearing caps and tighten them until they are finger tight.

Tighten the bearing cap screws / bolts to the specified torque, starting with the centre cap working alternately towards both ends of the block. (Fig. 136)

NB. After you have tightened the bolts of a bearing cap, turn the crankshaft. The

crankshaft must turn freely after all the main bearing caps are tightened down to the torque.

Refit the locking devices on the main bearing cap screws.(if applicable)

Check the crankshaft endplay.

There is the amount of thrust lengthwise on the crankshaft and this thrust is taken by one of the main bearings. (Fig. 137)

Fig. 136

Fig. 137







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To determine the endplay of the crankshaft, pry it forward at an adjacent main bearing by means of a screwdriver and then check the play using a feeler gauge or with a dial test indicator. (Fig. 138)

There are various reasons for end thrust, e.g. when the clutch pedal is depressed, the flywheel assembly and crankshaft are pushed forward

Too little endplay can the result of a misaligned thrust bearing, or dirt on the inner face of the bearing flange or thrust washer.

Too much endplay means that the thrust surfaces are worn and need replacement.

Fig. 138







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PRACTICE

Go to the sub-assembly and replace the camshaft and the crankshaft.

Ask your instructor to check your work and if you have achieved the required standards ask him to go on to the next section.

LEARNER

TRAINING OFFICER

Date:

Date:

Signed:

Signed:







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e) Assembling the piston assembly

Match up the pistons and rods according to their mark, so that they are in the correct relationship. (Fig. 139)

Heat the pistons in boiling water.

Wipe the pins with a clean cloth and coat them with clean engine oil.

Fit the rod over the pin and push the pin through the second boss. NB: If the pin is locked to the rod, ensure that the flat or groove in the pin lines up with

the lock screw in the rod.

If the pin is locked to the piston, line up the hole in the pin with the lock screw.

Fit the circlips or lock screw. (Fig. 140)

Fig. 139

Fig. 140







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NB: For more detail and instructions for different fits of piston pins refer to your workshop manual.

Fit the rings onto the piston by using a ring expander. (Fig. 141)

NB: Be careful not to open rings too much when installing too the piston. They are brittle and can brake easily.

Check that the rings are free and do not bend by moving them laterally and also by rotating them in the grooves.

For more detail refer to your workshop manual. Spacing the piston rings

Make sure the ring gaps (oil ring-rails and expander, compressor ring one and compressor ring two) are correctly spaced around the circumference of the piston. (Refer to your workshop manual).

NB: Basic rule: Stagger the ring gaps. Rotate the ring gaps so that the gaps on any two adjacent rings are half a circumference apart. (Fig. 142 on next page)

Fig. 141







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Apply a coat of engine oil to the circumference of each piston and rings.

Apply a coat of engine oil to the piston skirts and cylinder walls. This will facilitate smooth break-in when the engine is first started after reassembly.

Securely use a Ring Squeezer / Compressor to compress the rings into piston grooves. (Fig. 143)

When the rings are fully compressed, back the ratchet off one notch.

Fit the bearing inserts into the connecting rod and the connecting rod cups. (Fig. 144)

Fig. 142

Fig. 143

Fig. 144







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Apply a coat of engine oil to the upper bearing surfaces.

Use a hammer grip to push to push the piston in until the connecting rod makes contact with the crank pin(big-end).

At the same time rotate the crank until Bottom Dead Center.(BDC)

Align the bearing cap cylinder number marks and the connecting rod cylinder number marks. (Fig. 146)

Apply a coat of engine oil to the treads and setting faces of each connecting rod cap bolt.

Fig. 145

Fig. 146







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Tighten connecting rod bolts to the specified torque. (Fig. 147)

Fit oil pump with oil pipe

Install the oil pump with the oil pipe and tighten the bolts to the specified torque.

Note: Take care not to damage the 0-rings when tightening the oil pipe bolts. (Fig. 148)

Fig. 147

Fig. 148







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Oil pan

Fit oil pan and torque bolts to specification. (Fig. 149)

Flywheel

Fit flywheel and torque bolts to specification. (Fig. 150)

Fig. 149

Fig. 150







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b) Set the valve timing

Valve timing is the adjustment of the valves to open and close at the proper time for smooth and efficient operation of the engine. The crankshaft is the part around which the other parts are timed.

Summary The time valves in a 4-stroke engine cycle actually open and close can be measured by angles. These angles can be easily read using a valve-timing diagram.

Valve-timing principle (diagram) (Fig. 151 on next page)

To see how valve-timing works in a 4-stroke engine cycle, let’s show piston motion as a circle. In this simple cycle, each stroke is shown as a semi-circle. (Fig. 151)

This intake valve opens at top dead center, and closes at bottom dead center. The blue line shows that period and it matches the intake stroke. (Fig. 151)

The exhaust valve opens at bottom dead center, then closes at top dead center before the new air-fuel mixture enters the cylinder. (Fig. 151)

In practice, the intake valve usually opens earlier than top dead center, and stays open a little past bottom dead center.

The exhaust valve opens a little before bottom dead center, and stays open a little past top dead center.

When the valves actually open and close it can be measured by angles’. To make these angles easier to read, let’s use a spiral instead of a circl

The intake valve opens 12° before the piston reaches top dead center. (Fig. 151) And it closes 40° after bottom dead center. (Fig. 151)

The exhaust valve opens 47° before bottom dead center - and stays open - until 21° past top dead center. This gives exhaust gases more time to leave. (Fig. 151)

By the time the piston is at 47° before bottom dead center on the power stroke, combustion pressures have dropped considerably and little power is lost by letting the exhaust gases have more time to exit. (Fig. 151)







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When an intake valve opens before top dead center and the exhaust valve opens before bottom dead center, it is called lead.

When an intake valve closes after bottom dead center, and the exhaust valve closes after top dead center, it is called lag.

On the exhaust stroke, the intake and exhaust valve are open at the same time for a few degrees around top dead center. This is called valve overlap. On this engine, it is 33°.

NB: Different engines use different timings. Manufacturer specifications contain the exact

information.

This is done mainly by using one of the following designs, timing gears, timing chains or timing belts.

Timing marks Timing marks – lines, dots, circles or other shapes will be indented or cast into the timing gears, sprockets to use as references to align the timing marks. Timing marks on pulleys identify exact position of crankshaft to use as references to align and adjust valve timing. (Fig. 152 on next page)

Fig. 151







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Timing gears (example of a diesel engine) (Fig. 153)

Timing of gears

Timing of these gears is done by matching the timing marks when the gears are installed (Fig. 153)

Fig. 153

Fig. 152

BOTTOM DEAD CENTRE

BEFORE TOP DEAD CENTRE TOP DEAD CENTRE

AFTER TOP DEAD CENTRE







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Check the position of the keyway and timing marks on the gears.

Turn the crankshaft so that the keyway on both shafts will be in a position that when the gears are fitted the timing marks will line up.

Fit the fasteners to the gears. Inspection of gears

After you have fitted the gears, check the clearance between the gear teeth by using a dial gauge or by inserting a feeler gauge. (Fig. 154)

Before fit gears make inspect for worn gears and pitted gear teeth, broken gear teeth

Compare the clearance with the specifications in your workshop manual.

NB: For more detail and instructions refer to your workshop manual.

Fig. 154







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Timing chain and sprockets (Fig. 155)

Inspection of timing chain

Inspect for strech and replace if necessary.

Inspect for wear and replace if necessary.

Inspect tentioner for wear and replace if necessary.

Timing of timing chain

Timing of these chains is done by matching the timing marks when the sprockets are Installed.

Check the position of the keyway and timing marks on the sprockets.

Turn the crankshaft so that the keyway on both shafts will be in a position that when the sprockets are fitted the timing marks will line up.

Fit the fasteners to the sprockets.

Timing chain

Timing mark crankshaft Timing mark camshaft

Chain tensioner

Chain guide

Fig.155







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NB: After you have fitted the sprockets, check and adjust the tenstion of the chain by

adjusting the tensioner. For more detail and instructions refer to your workshop manual.

Camshaft driven by Timing belt and sprockets (Fig. 156)

Inspection of timing belt

Inspect for cracks.

Inspect for any signs of wear.

Inspect for missing or partially broken teeth on the underside of the belt.

Inspect idler pulley bearing for wear.

Inspect tensioner pulley bearing for wear.

Belt must be oil or grease free.

NB: Timing belts must be replaced at the manufacturer's recommended distance and/or time periods.

Fig. 156







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Failure to replace the belt can result in complete breakdown or catastrophic engine failure, especially in interference engines. The owner's manual maintenance schedule is the source of timing belt replacement intervals, typically every 60,000 to 100,000 km. It is common to replace the timing belt tensioner at the same time as the belt is replaced. The usual failure modes of timing belts are either stripped teeth.

Timing of timing belt

Timing of these belts is done by matching the timing marks when the pulleys are installed.

Check the position of the keyway and timing marks on the pulleys.

Turn the crankshaft so that the keyway on both shafts will be in a position that when the pulleys are fitted the timing marks will line up.

Fit the fasteners to the pulleys. NB: After you have fitted the pulleys, check and adjust the tension of the belt by adjusting

the tensioner. For more detail and instructions refer to your workshop manual.








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SELF TEST 8 Without referring to your notes, answer the following questions:

1. By means of a sketch explain how to space piston oil and compression rings. 2. Briefly explain “valve timing” _____________________________________________________________________

__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ _______________________________________________________________________________________________________________________________________________________________________________________________________________

2. Name the following abbreviations

TDC = ___________________________________ ATDC=__________________________________ BTDC = _________________________________ BDC = __________________________________







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3. Name the different checks/inspection on the following.

Timing chain: _______________________________________________________________________ _________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ Timing belt: _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ Timing gears: _________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ _____________________________________________________________________________________________________________________________________________________________________________________________________________________







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PRACTICE You should practice all the foregoing steps in assessing set the valve timing. Ask your Training Officer to check your work and to sign you off when it is correct.

REMEMBER ALWAYS WORK SAFE Once you have passed the entire self-tests and practices, you are now at liberty to request a Formative Assessment from your Assessor.

LEARNER

TRAINING OFFICER

Date:

Date:

Signed:

Signed:

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