How to Seal a Leaking Main Bearing

The main bearings in an engine support the crankshaft in the engine block and are completely enclosed by the oil pan. A leaking main bearing is actually a leaking seal located behind the rear main bearing. By virtue of its location, it is called a rear main bearing seal. When the seal gets worn, motor oil will leak out of the rear of the engine between the engine and transmission. Much disassembly is required.

Instructions

1

Park the vehicle on a level, paved surface and set the parking brake. Raise the front of the vehicle with a jack and support with jack stands.

2

Remove the transmission from the vehicle. This procedure will vary greatly, depending on what type of vehicle you have.

3

Place a drain pan under the drain plug on the oil pan. Use a ratchet and socket to remove the oil pan drain plug from the pan. Allow the engine oil to drain into the drain pan. Use a ratchet and socket to remove the bolts from the pan. Remove the pan from the engine.

4

Loosen the main bearing caps on all the main bearings about 1/8-inch with a ratchet and socket. Remove the bolts from the rear main bearing cap and remove the cap. You will see that one-half of the seal is in the cap and the other half is in the engine block.

5

Use a flat-head screwdriver to push on one edge of the seal so it rotates in its groove far enough so you can grab it and pull it out of the groove. Do this for both halves of the seal. You may have to use a pair of pliers to grab the half of the seal in the engine block. Note which way the lip of the seal faces so you can put the new seal in correctly.

6

Coat the new seal halves in motor oil. Slide the seal halves into their grooves. Use a flat-head screwdriver to finish pushing them into position. The ends of the seal halves will actually be ever so slightly above the surface of the bearing cap and engine block. This is so they form a good seal when pressed together.

7

Install the main bearing cap and bolts. Use a torque wrench and socket to torque all the cap bolts to the specification for your specific engine.

8

Remove the old oil pan gasket. Scrape any debris from the pan and engine block with a putty knife. Spray parts cleaner on a shop rag and clean the gasket surfaces on the pan and block.

9

Coat the side of the oil pan gasket that faces the oil pan with gasket sealer and mount the gasket on the oil pan. Rubber gaskets do not use sealer, only cork gaskets. The front and rear of the oil pan may have individual rubber gaskets. If so, mount them on the oil pan and apply a small bead of gasket sealer where the ends of the rubber gaskets meet the side gaskets on the oil pan. All rubber gaskets are usually one-piece.

10

Install the oil pan. Install and tighten the oil pan bolts with a ratchet and socket. Install the transmission. Fill the engine with fresh oil. Raise the vehicle, remove the jack stands and lower the vehicle to the ground.