Page 42 - REPOWER REFERENCE GUIDE (2020)

Engine Failure Diagnosis
Bearing Failures

Typical bearing failures are shown in the following illustration.

c
a b

d e

f
g
34209

a - Scratched by dirt
b - Dirt imbedded in bearing material
c - Tapered journal (overlay worn from entire surface)
d - Lack of oil (overlay partially worn off)
e - Worn area caused by radius ride
f - Bright or polished sections caused by improper seating
g - Craters or pockets caused by fatigue failure
When analyzing bearing failures, consider the following:
• Debris contamination on only specific bearings indicates that the debris broke loose from an area that is close to the
affected bearings and away from the unaffected bearings.
• Debris introduced via the oil cooler will affect all bearings: cam, main, and rod. Debris from an oil cooler will collect first at
the back of the engine, moving forward as the oil is pushed through the engine's oil passages.
NOTE: Oil from the oil cooler does not pass through the filter before entering the engine, and therefore any debris from the
cooler does not get filtered.
• An engine that has oil but has not been properly primed will have a dry block. Starting an engine in this state will result in
excessive wear at the front of the engine, with lesser wear occuring toward the rear of the engine and the oil pump.

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