Main and Connecting Rod Bearings

GENERAL INFORMATION

Main and connecting rod bearing wear types A. Scratches caused by dirt contamination B. Insufficient lubrication, local wiping C. Incorrect bearing installation F. Fatigue wear D. Taper of journals, bearing coating wiped off the entire surface along the length of the bearing E. Formation of a shoulder on the bearing edge

Inspection

PROCEDURE

1. Used bearings should be stored in their installed order for careful inspection, since wear marks on these parts allow the general condition of the engine to be assessed. Bearing shells are divided into size groups by thickness, indicated by color coding.

2. Causes of crankshaft bearing failure include insufficient lubrication, presence of dirt and foreign particles, engine overload and corrosion. Regardless of the cause of bearing failure, it must be eliminated before the engine is final assembled.

3. Remove the bearings from the cylinder block and lay the bearing shells out on a clean surface in the order of installation.

4. To prevent accelerated wear due to contamination, keep the engine clean during assembly. During operation, it is recommended to change the oil and filters more frequently.

5. With insufficient lubrication, the bearing coating material is wiped off the steel backing, and the bearing breaks up from overheating (a bluish tint is observed).

6. Under engine-stressing operating conditions (with the throttle fully open, or at low speed in a high gear), the bearing coating separates from the steel backing in small particles, and the bearings undergo fatigue wear.

7. Frequent short trips may cause corrosion wear of the bearings, since condensed moisture does not have time to evaporate due to insufficient engine warm-up.

8. Incorrect bearing installation during assembly also leads to premature wear. If the bearing clearance is less than specified, lubrication is hindered, which causes wear the same as from "oil starvation".

9. During assembly, do not touch the bearing shell surfaces with your fingers.

10. Main and connecting rod bearing shells must be replaced during an engine overhaul.