KMP Main Bearing Set U5MB0030C (0.030" undersize)

About this part

Main bearings carry the crankshaft in the block and hold it in line while it turns. Worn mains let the crank move, which loads the big ends, upsets oil pressure and eventually damages the block itself.

When to replace it

• A dull rumble from the bottom of the block at start-up
• Oil pressure that drops away as the engine warms
• Excessive crankshaft end float or movement
• Metal particles in the oil filter

Before you order

Keep shells in the order they come out if you are inspecting them: the wear pattern on each one tells you a lot about what went wrong.

Match the number stamped on the part you are removing, or the number in your engine or alternator manual, before ordering. Part numbers are shown for reference so the right replacement can be identified.

Questions