BabyBimmerAfter looking at the lead photo for this article on

3-sehes BMW service tips, you might get the impres

sion that the owners of these cars are a bunch of

crybabies. Quite the contrary. What we do mean tosay is that the information contained in this article

is intended to keep your Baby Bimmer customers

(who just might happen to be baby boomers them

selves) happy and pacified.

BMW introduced their new 3-series line in 1984

as a replacement for the late lamented 320i. Over the

years since then, there have been a staggering vari

ety of BMW models beginning with the number 3.

We've seen the 318i with its four cylinder M10B18

engine come and go, then come back again with an

all new engine. And there have been several differ

ent "small" six cylinder 325 models, using either the

2.7 liter M20B27 "eta" engine or the later 2.5 liter

M20B25 engine.

Once you've decided which engine is in the en

gine bay, the rest should be easy. The original 318i

uses a Bosch L-Jetronic fuel system, while all 325

models have a Bosch Motronic engine management

system. The 318i only lasted for two years, so most

of our engine tips will deal with the more common

six cylinder 325 models. We'll note any differences

in this area where necessary.

All 3-series models, in both four or six cylinder

varieties, share the same basic body and running

gear design. Something of a rarity for a small car

today, 3-series BMWs still steadfastly cling to rearwheel drive.

Many of the performance and safety features

found on larger BMWs have been squeezed into the

3-series body style. You're likely to find ABS, an air

bag, a Check Control Panel, and some power acces

sories on a late model 325. This may be an entry

level BMW, but it's still a BMW.

All of this complexity hasn't seemed to affect

basic 3-series reliability. While electrical problems

aren't unheard of on these cars, they can usually be

solved using basic troubleshooting techniques. Look

for damaged or corroded wiring or wiring connec

tors to cause electrical problems more often than

actual component failures.

BMW revived the 318i last year with an all new

twin-cam, four cylinder engine with four valves per

cylinder. Service information about any problem ar

eas with this engine is still pretty scarce. An all new

re-bodied 3-series line is also scheduled for release

this year. We'll keep you posted before these newer

models start driftmg into your shop.

By The Numbers

We've arranged our 3-series information into

three loose categories. The first group of photos and

captions deals with several items you should be

aware of while performing basic 3-series mainte

nance. Using these tips will help you recognize prob

lems before they have a chance to cause your cus

tomer any inconvenience.

The middle group of photos covers several elec

trical tips to get you pointed in the right direction.

Then we'll finish up with undercar steering, suspen

sion, and brake information.

The 3-series BMW is a rugged piece of machinery

that's designed for use as an every day driver rather

than a pampered play toy. We hope the information

in this article will help your customers enjoy many

miles of trouble-free driving while making your life

a little easier in the bargain.

— By Callan Campbell

i

The six cylinder engine will bend valves if the timingbelt breaks. These belts can break before the recommended 60,000 mile change interval. Changing the

belt at least every four years or 50,000 miles shouldprevent expensive surprises like this. Also check for

water pump leakage during belt replacements.

Two timing belt lengths, several cam sprockets, andtwo belt tensioner designs have been used on the

six. Some of the earlier parts are no longer available.

Only parts marked "Z 127" should used. Later timing belts are one tooth shorter and slightly wider,and must be used with the later tensioner design.

Baby Dimmer

3

The stamped steel camshaft sprocket marked

"Schroth" installed on early sixes had a habit of

breaking loose from its center hub. A blue dot on the

thermostat housing and a round driver's door pillar

label with the number 14 punched out mean the

sprocket has already been replaced under warranty.

Worn rocker arm bushings and rocker shafts can

cause noisy valve train operation. Wiggle the rockers to check for excessive clearance. Rocker feet and

cam lobes may also wear on low maintenance en

gines. Always replace the rubber rocker shaft seals

at both ends of the head during valve adjustments.

7

The oil filter housing bottom cap is a spot to watch

for oil leaks on later 325s. A seal kit is available to

repair housing leaks. It's easier to remove the hous

ing first, then replace the seal with the housing held

in a vice. All housing seals should also be replaced

during reassembly to prevent other leaks.

Remove the radiator fan and fan clutch to reach the

six cylinder cap and rotor. This fan clutch tool slips

over the water pump pulley bolts to keep the pump

from turning. Then a thin 32 mm wrench is used to

loosen the left hand thread fan clutch nut. Now re

move the fan clutch, fan, and shroud.

6

The four and six cylinder engines both use an eccen

tric valve adjustment system. On a new engine, the

eccentric cam adjusting holes (arrow) will point

almost straight up. Start looking for worn valve train

parts if the adjuster is turned all the way around and

the clearance still isn't right.

8

Engine vibration may crack this exhaust system

mount at the rear of the transmission. Transmission

leaks may not be caused by a leaking output shaft

seal. Check the selector shaft seal directly above the

output shaft. Also make sure the shifter console

mount bolts at the top of the transmission are tight.

Baby Bimmer

9

Six cylinders also like to leak along the right edge of

the head gasket. There are several oil return pas

sages along this edge that drain oil from the head

back to the oil pan. Replacement head gaskets with a

printed seal around the oil returns are designed to

prevent leakage in this area.

Check for cracks in the short hose between the inlet

fuel hose union and the cold start injector. Other fuel

hoses may also harden and crack due to high

underhood temperatures. Replace damaged hoses as

necessary, using the correct hose clamps. Small fuel

leaks may go unnoticed until they cause an engine fire.

The six cylinder's thermostat housing elbow (arrow)

can loosen and cause an intermittent coolant leak.

Replacing the housing is safer than trying to glue the

loose elbow back into place. Remove the coolant

sensor, then loosen the fuel rail bolts to reach the

thermostat housing bolts.

Be careful when changing the gas filter on 318i and

early 325 models. The filter is mounted near the

starter and must be removed from below. It's very

easy to touch the starter's battery terminal with the

aluminum filter and risk more than a spark. The filter

was moved to the rear axle area on later 325 models.

Carefully inspect the area around the spark plugs

before removing the plugs. The plugs face downward

in the cylinder head, so a loose part could end up

dropping through the spark plug hole. Remove the

plug in the six cylinder exhaust manifold (arrow) to

check emissions ahead of the catalytic converter.

A faulty vacuum advance solenoid (arrow) on early

318i models may leak vacuum to the distributor at

idle, affecting advance operation. Early solenoids

receive manifold vacuum and battery voltage while

the engine is running. The control unit grounds the

solenoid to open the solenoid above idle speed.

Baby Bimmer

Later 318i models have a different distributor and

vacuum control solenoid. The updated solenoid con

trols a ported vacuum signal. So even if the solenoid

leaks, the timing can't advance at idle. The later

solenoid design must only be used with the revised

distributor and a ported vacuum source.

A no start condition at low outside temperatures on

325e models built before October 1985 may be

caused by a misrouted cable at the firewall-mounted

battery junction block. The cable (left arrow) should

be routed as shown, not connected to the terminal at

the opposite end of the block (right arrow).

The 318i and 1984-7 325 models have a separate idle

control unit to maintain the idle speed. A poor con

nection between the control unit and its harness con

nector may trick you into blaming the idle control

unit for idle speed problems. Plugging in a new con

trol unit may temporarily repair the loose connection.

A set of jumper leads with matching terminals

should be used for tapping into the diagnostic con

nector. Use a remote starter switch for valve adjust

ments by attaching the leads to terminals 11 and 14.

The second jumper set fits the black diagnostic

connector's smaller terminals on later 325s.

The black plastic idle control valves on 318i and

325e models can fool you because they lack an ex

ternal adjusting screw. These valves can be adjusted

by turning the small screw inside the valve. Shunt

into the control valve wiring with jumper leads to

measure the milliamp reading with a DVOM.

20

This large female connector at the A pillar is a good

place to check when diagnosing power window or

door lock problems. Water can get inside the con

nector and cause wiring corrosion. Corroded pin ter

minals can be replaced separately. The door harness

should be replaced if many terminals are damaged.

Baby Bimmer

21

The connector must be properly reinstalled after re

pairs or water will leak in again and spoil your work.

Slip the protective boot over the male door harness

connector first. Make sure the boot fits tightly over

the connector. Now reattach the male door connec

tor to the female connector at the A pillar.

A brake pad warning light that flickers or stays lit

(even though the pads aren't worn out) may be caused

by damaged brake pad wear sensor wiring. Sensor wir

ing often breaks inside the insulation. The open circuit

causes the warning light to come on. Someone has

already bypassed the damaged wiring to this sensor.

If the wiring is broken on the body harness side ofthe sensor connector, cut the body harness about an

inch away from the connector boot. Solder an old

pad sensor connector into the harness. Use heat

shrink tubing to cover the splice. Trim the harness

connector so it fits into the pad sensor connector.

Fuel pump noises may be caused by the transferpump inside the tank going bad, rather than a main

pump failure. The rubber boot connecting the trans

fer pump to the metal supply pipe may also split.

The leaking boot causes the main pump to suck air

when there's less than a third of a tank of gas.

Defective main and fuel pump relays can cause inter

mittent stalling problems. The relay closes, but pitted

contacts won't pass current through the relay. Tap

ping on the relay may cause the engine to stall. On six

cylinder models, the main relay powers the Motronic

control unit and the fuel pump relay windings.

The sealed front wheel bearings are normally

replaced as an assembly. Bearings and hubs are

available separately, however. If a new bearing is

installed inside a used hub, make sure the outer

bearing race fits tightly inside the hub. If not, the

race may turn inside the hub and ruin the bearing.

Baby Bimmer

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27

Check for sagged or broken lower control arm bush

ings (arrow) if the steering shudders when the brakes

are applied. Install new bushings with the arrow

pointing toward the notch on the arm. Grinding a

slight chamfer on one edge of the bushing will help

start it into the arm. Replace bushings in pairs.

Some brake pad compositions can also cause front

steering and suspension vibrations during braking.

Hard pads seem to transmit even slight rotor surface

variations to the steering wheel when decelerating

quickly with hot brakes. Worn suspension parts will

amplify these vibrations.

Mitchell On-Demand Repair Information System.

Circle No. 114 on Reader Service Card

Clunking noises from the rear suspension may be

caused by worn upper shock mount bushings. Worn

bushings let the shock wobble around over bumps. If

the clunking is ignored, the upper mount may dis

connect from the body and really make a racket. The

bushings are available without replacing the shocks.