Jeep CJ/Scrambler 1971-1986 Repair Guide

Rear Main Oil Seal

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REPLACEMENT



See Figure 1

4-134 Engine
  1. Raise and support the vehicle on jackstands.
  2.  
  3. Remove the oil pan.
  4.  
  5. Remove the rear main bearing cap.
  6.  
  7. Using a center punch, drive the upper seal out of its groove just far enough to grasp it with a pliers, and pull it the rest of the way.
  8.  

To install:
  1. Apply a light film of chassis grease to the lower seal and install it in the cap.
  2.  
  3. Install the rubber packings in the upper crankcase half. The packings are of a predetermined length to allow about 1 / 4 in. (6mm) protrusion. This protrusion is necessary for a positive seal. DO NOT TRIM THESE SEALS!
  4.  
  5. Apply a small amount of RTV sealant to both sides and face of the bearing cap and install it.
  6.  
  7. Torque the cap to the figure shown in the torque specifications chart.
  8.  
  9. Install the oil pan.
  10.  

6-225 Engine

For removal of both upper and lower seals, the crankshaft must be removed from the engine. Crankshaft removal is easiest with the engine out of the vehicle.

  1. Remove engine.
  2.  
  3. Remove the timing case and gears, and any spacers and shims from the front of the crankshaft.
  4.  
  5. Remove the oil pan and oil pickup.
  6.  
  7. Note the mating of crankshaft and main caps. Match mark them with an indelible inker.
  8.  
  9. Unbolt the #1 main bearing cap. Using a pry bar, carefully lift the cap from the dowels. Take great care to avoid damaging the dowels. Any bent dowels must be replaced.
  10.  
  11. In the same manner, remove the next two caps.
  12.  
  13. To remove the rear cap, rear main bearing bolt remover, special tool W-323 or its equivalent must be used.
  14.  
  15. Match mark the connecting rod caps and remove them.
  16.  
  17. Lift out the crankshaft.
  18.  
  19. Remove the braided seal from the inner groove of the cap and the neoprene seals from the outer grooves.
  20.  
  21. Using a center punch, drive the block seal out just far enough to grasp with a pliers and pull out.
  22.  

To install:
  1. Dip a new block seal in engine oil and force it into place in the block.
  2.  
  3. Insert the new braided cap seal into the groove in the cap and coat it with engine oil.
  4.  
  5. Cut the ends of the braided seals flush with the cap and block surfaces.
  6.  
  7. The new neoprene seals are installed after the cap is torqued in place. These seals are supposed to project about 1 / 16 in. (1.6mm) above the cap. DO NOT CUT THESE SEALS FLUSH WITH THE CAP! Before installation, dip the neoprene seals in kerosene for about 1-2 minutes. After installation squirt some more kerosene on the protruding ends of the seals. Then, peen the ends of the seals with a hammer to make sure of a tight seal at the upper parting line between the cap and block.
  8.  
  9. Installation of the crankshaft and remaining parts is the reverse of removal. Torque the main cap bolts evenly, one side then the other, a little at a time until the torque value is reached.
  10.  

Whenever the second cap is removed, the thrust surfaces must be aligned. To do this, pry the crankshaft back and forth several times throughout its end travel with the cap bolts of the second main cap only finger tight.

4-150 Engine
  1. Remove the transmission.
  2.  
  3. Remove the flywheel.
  4.  
  5. Pry out the seal from around the crankshaft flange.
  6.  

To install:
  1. Coat the inner lip of the new seal with clean engine oil.
  2.  
  3. Gently tap the new seal into place, flush with the block, using a rubber or plastic mallet.
  4.  
  5. Install the flywheel.
  6.  
  7. Install the transmission.
  8.  

4-151 Engine

The seal is a one piece unit that can be removed and installed without removing the oil pan or crankshaft.

  1. Raise and support the vehicle on jackstands.
  2.  
  3. Remove the transmission and transfer case as an assembly.
  4.  
  5. Disconnect and remove the starter.
  6.  
  7. On manual transmission vehicles, remove the flywheel inspection plate, and clutch slave cylinder.
  8.  
  9. Remove the flywheel or drive plate housing.
  10.  
  11. On manual transmission, remove the clutch assembly by backing out the bolts evenly around the pressure plate.
  12.  
  13. Remove the flywheel or drive plate. It is a good idea to match mark the flywheel location for assembly.
  14.  
  15. Using a small bladed screwdriver, pry the rear seal out from around the crankshaft hub. Be careful to avoid damaging the sealing groove or hub.
  16.  

To install:
  1. With a light hammer, tap the seal into position with the lip facing the front of the engine.
  2.  
  3. Install the flywheel or drive plate.
  4.  
  5. On manual transmission, install the clutch assembly by tightening the bolts evenly around the pressure plate.
  6.  
  7. Install the flywheel or drive plate housing.
  8.  
  9. On manual transmission vehicles, install the flywheel inspection plate, and clutch slave cylinder.
  10.  
  11. Install the starter.
  12.  
  13. Install the transmission and transfer case as an assembly.
  14.  



Click image to see an enlarged view

Fig. Fig. 1: Rear main seal installation on the 6-232, 6-258 and 8-304 engines

6-232, 6-258 and 8-304 Engines

This seal is a two piece neoprene type with a single lip.

  1. Raise and support the vehicle on jackstands.
  2.  
  3. Remove the oil pan.
  4.  
  5. Remove the rear main bearing cap and discard the lower seal.
  6.  
  7. Loosen all remaining main bearing caps.
  8.  
  9. Using a center punch, carefully drive the upper half of the seal out of the block just far enough to graph with a pliers and pull out.
  10.  
  11. Remove the oil pan front and rear seals and the side gaskets.
  12.  

To install:
  1. Clean all gasket surfaces.
  2.  
  3. Wipe clean the sealing surface of the crankshaft and coat it lightly with engine oil.
  4.  
  5. Coat the lip of the upper seal with engine oil and install it in the block. The lip faces forward.
  6.  
  7. Coat both end tabs of the lower seal with RTV silicone sealer. Do not get any RTV sealer on the seal lip.
  8.  
  9. Coat the outer curved surface of the seal with liquid soap. Coat the seal lip with engine oil.
  10.  
  11. Install the seal into the cap, pressing firmly.
  12.  
  13. Coat both chamfered edges of the cap with RTV sealer.
  14.  


WARNING
Do not allow any RTV sealer to get on the mating surfaces of the cap or block as this will affect bearing clearance!

  1. Install the rear main cap.
  2.  
  3. Tighten all main bearing cap bolts gradually to 80 ft. lbs.
  4.  
  5. Replace the oil pan.
  6.  

 
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