chapter 11 crack detection repai
DESCRIPTION
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Crack detection & repair
Causes of cracks in heads & blocks• Overheating
• Freezing• Expansion and contraction• Cracks start from water jacket side
Only heads and blocks are repaired
Copyright 2003 Gary Lewis – Dave Capitolo
Crack detection & repair
Design & production problems• Core shifts
• Sharp corners after machining• Siamese valves & ports
Crack detection & repair
Dry magnetic particle inspection for iron parts• Clean area to base metal
• Set up magnetic field on part• Dust with magnetic powder • Cracks will be visible• Test in different directions
Crack detection & repair
Wet magnetic particle inspection• For connecting rods & crankshafts• Clean parts to base metal• Part is magnetized under black light• Spray with solvent carrying magnetic particles• Cracks become visible
• Part can then be demagnetized
Crack detection & repair
Dye penetrants• Used on all materials• Clean parts to base metal• Coat part in penetrant• Wait a few minutes and wipe off excess• Spray part with developer & allow to dry to a powder
Crack detection & repair
Pressure testing castings• Used for heads & blocks on all materials• Water passages are blocked with plates• Pressurize passages to 3 times cooling system pressure• Spray part with soapy water or submerge part
Crack detection & repair
Crack repair pins• Full length must be accessible with drill & tap• Locate the crack• Drill 1/8” hole past each end of the crack• Drill & tap holes• Use tapered reamer to make tapping easier
Crack detection & repair
Sleeving cracked cylinders
• 1/8” and 3/32” wall sleeves• .002” average interference• Press or shrink
Crack detection & repair
Sleeving other holes
• Head bolt holes• Oil passages
Crack detection & repair
Stop drilling
• Drill 1/8” hole past crack• Not done near water, oil, or combustion chamber
Crack detection & repair
Welding Aluminum
• TIG• Prepare crack by gouging
• Preheat casting• Gas acts as a shield
Crack detection & repair
Welding Iron, method #1
• Oxy-acetylene torch• Preheat part to 1300ºF
• Iron filler rod
Crack detection & repair
Welding Iron, method #2
• Flame spray welding• Gouge area
• Preheat casting to 650ºF
• Heat area red hot & introduce powder
Crack detection & repair
Sealing
• Sodium silicate• Heated & circulated for an hour
• Pressurized to 55 psi
• Cures in air in 24 hours
• Used to repair porosity problems• Can be added to cooling system
Crack detection & repair
Vacuum impregnation
• Vacuum applied to resin filled tank • Pressure applied
• Rinsed in water