Rear Main Seal Replacement
Contributed By: Joe Schaefer
This is from the 1973 Jeep Technical Service Manual J-73-1001 and applies to all 258/304/360 and 401 engines.
The rear main bearing crankshaft seal consists of a two piece neoprene single lip seal to effectively seal the rear of the crankshaft. Correct installation of the seal will insure leak free engine operation
Removal and Installation
- Drain the engine oil and remove the oil pan.
- Remove the oil pan front and rear neoprene oil seals.
- Remove the oil pan side gaskets.
- Thoroughly clean the gasket surfaces of the oil pan and engine block.
- Remove all sludge and dirt from the oil pan sump.
- Remove the rear main bearing cap.
- Remove and discard the lower seal.
IMPORTANT: To ensure leak free operation, the upper and lower seal halves must be replaced in pairs.
- Clean the main bearing cap thoroughly to remove all sealer.
- Loosen all remaining main bearing caps.
- With a brass drift and hammer, tap the upper seal until sufficient seal is protruding to permit pulling the seal out completely.
- Wipe the seal surface of the crankshaft clean; then oil lightly.
- Coat the block contacting surface at the upper seal with soap, and the lip of the seal with engine oil.
- Install the upper seal into the engine block.
CAUTION: The lip of the seal must face to the front of the engine.
- Coat both sides of the lower seal end tabs with "Permatex" No. 2 or equivalent, being careful not to apply sealer to the lip of the seal.
- Coat the outer curved surface of the lower seal with soap and the lip of the seal with engine oil.
- Install the seal into the cap recess and seat it firmly.
- Place "Permatex" No. 2, or equivalent, on both chamfered edges of the rear main bearing cap.
- Install the rear main bearing cap and inserts.
- Tighten all main bearing cap screws to the specified torque.
- Install oil pan using new gaskets and seals.
- Tighten the drain plug securely.
- Use new engine oil to fill the crankcase to the specified level.