Analysis of scratches and metal particles on the inner surface of the bearing after operation

Appearance：

（1）Scratch marks may be visible on the bearing surface, which are caused by large or hard metal particles sandwiched between the inner surface of the bearing and the journal in the oil film during the operation of the machine, resulting in scratches on the surface of the bearing during relative operation.

（2）Foreign particles are embedded in the lining of the bearing. The bearing shell is a sliding bearing, which not only has high temperature resistance and wear resistance, but also has an important performance of embedding. During the operation of the machine, some sharper, harder, and smaller particles mixed into the oil will embed into the surface of the bearing shells. It is this important feature that better protects the axial journal from damage.

Possible Causes:

1．Improper cleaning of the engine and parts prior to assembly.

2．Road dirt and sand entering the engine through the air-intake manifold or faulty air filtration.

3．Wear of other engine parts, resulting in small fragments of these parts entering the engine’s oil supply.

4．Neglected oil filter and/or air filter replacement.

What can we do?

1. Install new bearings, being careful to follow proper cleaning procedures.

2. Grind journal surfaces if necessary.

3. Recommend that the operator have the oil, air filter, oil filter and crankcase breather-filter replaced as recommended by the manufacturer.