Rear Main Bearing Oil Seal Replacement

Written by: Mike Ervin

The following steps are needed for replacemnt of the rear main bearing oil seal.


Note:  Always replace the upper and lower seal as a unit.

The rear main bearing oil seal can be replaced (both halves) without removal of the crankshaft.  Extreme care should be exercised when installing this seal to protect the sealing bead located in the channel on the outside diameter of the seal.  An installation tool (usually included with the new seal) must be used to protect the seal bead when positioning seal as follows:

1.   With the oil pan and oil pump removed, remove the rear main bearing cap.

2.   Remove oil seal from the bearing cap by prying from the bottom with a small screwdriver.

3.   To remove the upper half of the seal, use a small hammer to tap a brass pin punch on one end of seal until it protrudes far enough to be removed with pliers.

4.   Clean all sealant and foreign material from cylinder case, bearing cap and crankshaft, using a non-abrasive cleaner.

5.   Inspect components for nicks, scratches, burrs and machining defects at all sealing surfaces, case assembly and crankshaft.

6.   Coat seal lips and seal bead with light engine oil.  Keep oil off seal mating ends.

7.   Position tip of tool between crankshaft and seal seat in cylinder case.

8.   Position seal between crankshaft and tip of tool so that seal bead contacts tip of tool.  Make sure that oil seal lip is positioned toward front of engine.

9.   Roll seal around crankshaft using tool as a "shoe-horn" to protect seal bead from sharp corner of seal seat surface in cylinder case.  Installation tool must remain in position until seal is properly positioned with both ends flush with block.

10.  Remove tool, being careful not to withdraw seal.

11.  Install seal half in bearing cap, again using tool as a "shoe-horn", feeding seal into cap using light pressure with thumb and finger.

12.  Install bearing cap to case with sealant applied to the cap-to-case interface being careful to keep sealant off the seal split line.

13.  Install the rear main bearing cap (with new seal) and torque to 10-12 lb. ft..  Tap end of crankshaft first rearward then forward with a dead blow hammer.  This will line up the thrust surfaces.  Retorque bearing cap to 70 lb. ft..