Jeep CJ 1945-1970 Repair Information

Rear Main Oil Seal

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REPLACEMENT



4-134 Engines

See Figure 1



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Fig. Fig. 1: Rear bearing cap packing used in late L-head and all F-head 4-134 engines

On early L-head 4-134 engines, the rear bearing is sealed by a wick packing. This packing is installed in a groove machined into the rear main bearing cap. On later L-head 4-134 and all F-head 4-134 engines, a steel-backed lip seal is used. This seal can be used to replace the older wick seal, and can be replaced without removing the crankshaft.

WICK-TYPE SEALS
  1. Remove the engine from the vehicle.
  2.  
  3. Remove the timing chain cover and crankshaft timing gear.
  4.  
  5. Remove the oil pan and pick-up unit.
  6.  
  7. Slide the thrust washers and adjusting shims off the front end of the crankshaft.
  8.  
  9. Move the two pieces of the rear main cap packing away from the sides of the cap.
  10.  
  11. Note the numbers of the main caps and block for position when installing.
  12.  
  13. Unbolt and remove the main bearing caps.
  14.  


WARNING
Take great care in removing the caps. Lift them evenly and avoid binding on the dowels. If you suspect that any of the dowels were bent during removal, replace them.

  1. Unbolt and remove the connecting rod caps, taking care to note their position for installation.
  2.  
  3. Lift out the crankshaft.
  4.  
  5. Remove the rear main seal wicking from the grooves.
  6.  
  7. If a steel-backed lip-type seal is being used to replace the older style wicking, go on to the next procedure for later L4-134 and all F4-134 engines. If a wick-type seal is being used, clean the seal grooves, and insert the seal in the grooves with your fingers.
  8.  
  9. Using a round piece of wood, roll the seal tightly into the groove starting at one end and working toward the center, then the other end toward the center.
  10.  
  11. A small portion of the packing will protrude above the surface of the cap. This should be cut off flush with the cap at each end.
  12.  

LIP-TYPE SEALS

The following procedure should be used for later L4-134 and all F4-134 engines with steel-backed lip type seals.

  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.  
  9. Apply a light film of chassis grease to the lower seal and install it in the cap.
  10.  
  11. 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!
  12.  
  13. Apply a small amount of RTV sealant to both sides and face of the bearing cap and install it.
  14.  
  15. Tighten the cap to the figure shown in the torque specifications chart.
  16.  
  17. Install the oil pan.
  18.  

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 the engine form the vehicle as described earlier in this section.
  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 pick-up.
  6.  
  7. Note the mating of crankshaft and main caps. Matchmark them with an indelible ink marker.
  8.  
  9. Unbolt the No. 1 main bearing cap. Using a prybar, 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. Matchmark 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.  
  23. Dip a new block seal in engine oil and force it into place in the block.
  24.  
  25. Insert the new braided cap seal into the groove in the cap and coat it with engine oil.
  26.  
  27. Cut the ends of the braided seals flush with the cap and block surfaces.
  28.  
  29. The new neoprene seals are installed after the cap is tightened in place. These seals are supposed to project about 1 / 16 in. (1.5875mm) above the cap. Do not cut these seals flush with the cap! Before installation, dip the neoprene seals in kerosene for about 12 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.
  30.  
  31. Installation of the crankshaft and remaining parts is the reverse of removal. Tighten the main cap bolts evenly, one side then the other, a little at a time until the torque value is reached.
  32.  

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.