Trouble Shooting Chart
1. Loose motor or com-
Loose motor or compressor pulleys are a very common cause of
compressors knocking. Tighten pulley clamp bolt and set screws.
2. Lack of oil in crankcase.
Check for proper oil level; if low, check for possible damage, to
bearings. Dirty oil can cause excessive wear.
3. Worn connecting rod
Remove connecting rod cap and inspect bearings; if worn or
4. Worn piston pin bushing.
Remove rod and piston assemblies from the compressor and
inspect for excess wear. Replace excessively worn piston pin or
pistons, as required.
5. Burned out bearings.
Replace worn or burned out bearings and remedy cause of
failure, (usually insufficient or dirty oil).
6. Excessive crankshaft
Remove the cylinder and head assemblies from the running gear
and check crankshaft for end play. If end play can be felt, remove
one thin bearing adjustment shim (where used) at a time, and
recheck end play after each removal. The bearing, when properly
adjusted, should have a very slight drag when turned over by
hand. This adjustment should never be made while the rods are
still connected to the crankshaft.
7. Loose valve assembly.
Remove valve assembly and valve assembly gasket from the
head, replace valve assembly gasket with a new one, and
reinstall valve assembly after examining the valve pockets in
the head and the valve assemblies for possible damage.
Carefully tighten valve assembly holddown screws sufficiently
to hold the valve solidly in place.
8. Piston hitting the head.
Remove the compressor head and inspect for carbon deposits
or other foreign matter on top of the piston. Replace head with
new head gasket and intercooler gaskets if necessary.
9. Noisy check valve:
Oil in the
1. Worn piston rings.
Replace with new rings.
2. Compressor air intake
Clean filter. Check for other restrictions in the intake system,
3. Restricted breather.
Clean and check breather valve for free operation.
4. Excessive oil in com-
Drain down to full level.
5. Wrong oil viscosity.
Check lubrication section of this manual for correct viscosity.
6. Connecting rod out of
Have rod with piston attached checked and realigned. Most
automotive engine rebuilding houses have equipment available
to make this test.
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