GM Cadillac 1967-1989 Repair Guide

Rear Main Oil Seal

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REMOVAL & INSTALLATION



Except 6-252, 1986-89 8-250, 8-273, 8-307 and 8-350 Engines

See Figures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11

  1. Remove the oil pan.
  2.  
  3. Remove the rear main bearing cap and loosen the bolts holding the other four bearings about three turns each. Remove the old rear main bearing seals.
  4.  

To install:
  1. Clean the groove in the cap and in the block. Lubricate seals with engine oil.
  2.  
  3. Make an installation tool.
  4.  
  5. Start the upper half into the groove in the block with the lip facing forward and rotate it into position, using the tool as a guide. Press firmly on both ends to be sure it is protruding uniformly on each side.
  6.  
  7. Install the lower half of the seal into the bearing cap with the lip facing forward and one end of the seal over the ridge and flush with the split line. Hold one finger over this end to prevent it from slipping, and push the seal into seated position by applying pressure to the other end. Be sure the seal is firmly seated and protrudes evenly on each side. Do not apply pressure to the lip. This may damage the effectiveness of the seal.
  8.  

On vehicles equipped with neoprene type seals, make sure that the seal is flush at the split line to avoid leaks.

  1. Apply rubber cement to the mating surfaces of the block and cap being careful not to get any cement on the bearing, the crankshaft or the seal. The cement coating should be about 0.010 in. (0.25mm) thick.
  2.  
  3. Tighten the bearing bolts to 89 ft. lbs. (121 Nm) for the 250 and 90-100 ft. lbs. (122-136 Nm) for all others. Be sure to tighten the bolts of the other four bearings also. Rotate the crankshaft one full turn to check for binding.
  4.  
  5. Reinstall the oil pan.
  6.  

6-252 Engine

On the 6-252 engine, the factory recommends removing the crankshaft to replace the upper seal, but the seal can be replaced using the method below.

  1. Remove the oil pan and the rear main bearing cap.
  2.  
  3. Loosen the rest of the crankshaft main bearings slightly and allow the crankshaft to drop about 1 / 16 in. (1.5mm), no more.
  4.  
  5. Remove the old upper half of the oil seal.
  6.  
  7. Wrap some soft copper wire around the end of the new seal and leave about 12 in. (305mm) on the end. Lubricate the new seal generously with clean oil.
  8.  
  9. Slip the free end of the copper wire into the oil seal groove and around the crankshaft. Pull the wire until the seal protrudes an equal amount on each side. Rotate the crankshaft as the seal is pulled into place.
  10.  
  11. Remove the wire. Push any excess seal that may be protruding back into the groove.
  12.  
  13. Before tightening the crankshaft bearing caps, visually check the bearings to make sure they are in place. Torque the bearing cap bolts to specification. Make sure there is no oil on the mating surfaces.
  14.  
  15. To replace the seal in the main bearing cap, remove the old seal and place a new seal in the groove with both ends projecting above the mating surface of the cap.
  16.  
  17. Force the seal into the cap groove by rubbing down on it with a hammer handle or other smooth round tool, until the seal projects above the groove not more than 1 / 16 in. (1.5mm). Using a razor blade, cut the ends off flush with the surface of the cap.
  18.  
  19. Place new neoprene seals in the grooves in the sides of the bearing caps after soaking the seals in kerosene for two minutes.
  20.  

The neoprene seals will swell up once exposed to the oil and heat. It is normal for the seals to leak for a short time, until they become properly seated. The seals must NOT be cut to fit.

  1. Reverse the above procedure for installation. Use a small bead of sealer on the outer edge of the bearing cap mating surface.
  2.  
  3. Install the oil pan. Run the engine at low rpm for the first few minutes of operation.
  4.  

1986-89 8-250 and 8-273 Engines

To perform this procedure, use a Seal Removal tool No. J-26868 or equivalent, and a Seal Installer tool No. J-34604 or equivalent.

  1. Remove the transaxle.
  2.  
  3. Unbolt and remove the flexplate from the rear end of the crankshaft.
  4.  
  5. Using a Seal Removal tool No. J-26868 or equivalent, remove the old seal. Thoroughly clean the seal bore of any leftover seal material with a clean rag.
  6.  
  7. Lubricate the lip of a new seal with wheel bearing grease. Position it over the crankshaft and into the seal bore with the spring facing inside the engine.
  8.  
  9. Using a Seal Installer tool No. J-34604 or equivalent, press the seal into place. The seal must be square (this is the purpose of the installer) and flush with the block to 1mm indented.
  10.  
  11. To complete the installation, reverse the removal procedures. Torque the flexplate-to-crankshaft bolts to 37 ft. lbs. (50 Nm). Refill the crankshaft. Operate the engine and check for leaks.
  12.  

8-307, 8-350 Gasoline and Diesel Engines

The crankshaft need not be removed to replace the rear main bearing upper oil seal. The lower seal is installed in the bearing cap.

  1. Drain the crankcase oil and remove the oil pan and rear main bearing cap.
  2.  


CAUTION
The EPA warns that prolonged contact with used engine oil may cause a number of skin disorders, including cancer! You should make every effort to minimize your exposure to used engine oil. Protective gloves should be worn when changing the oil. Wash your hands and any other exposed skin areas as soon as possible after exposure to used engine oil. Soap and water, or waterless hand cleaner should be used.

  1. Using a special main seal tool or a tool that can be made from a dowel (see illustration), drive the upper seal into its groove on each side until it is tightly packed. This is usually 1 / 4 - 3 / 4 in. (6-19mm).
  2.  
  3. Measure the amount the seal was driven up on one side; add 1 / 16 in. (1.5mm), then cut this length from the old seal that was removed from the main bearing cap. Use a single-edge razor blade. Measure the amount the seal was driven up on the other side; add 1 / 16 in. (1.5mm) and cut another length from the old seal. Use the main bearing cap as a holding fixture when cutting the seal as illustrated. Carefully trim protruding seal.
  4.  
  5. Work these two pieces of seal up into the cylinder block on each side with two nailsets or small screwdrivers. Using the packing tool again, pack these pieces into the block, then trim them flush with a razor blade or hobby knife as shown. Do not scratch the bearing surface with the razor.
  6.  
  7. Install a new seal in the rear main bearing cap. Run a 1 / 16 in. (1.5mm) bead of sealer onto the outer mating surface of the bearing cap. Assemble the cap to the block and torque to specifications.
  8.  



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Fig. Fig. 1: Installing rear main bearing oil seal



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Fig. Fig. 2: Rear main bearing oil seal installation tool



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Fig. Fig. 3: Make a rear main bearing seal tool shown from a wooden dowel as shown



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Fig. Fig. 4: Cutting off the lower seal ends



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Fig. Fig. 5: Packing the oil seal



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Fig. Fig. 6: Removing the lower rear main seal



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Fig. Fig. 7: 6-252 lower rear main bearing cap sealer application - do not over-apply



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Fig. Fig. 8: Removing the upper main seal



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Fig. Fig. 9: Rear main oil seal removal tool - 1986-89 8-250, 8-273 engine



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Fig. Fig. 10: Rear main oil seal installation tool - 1986-89 8-250, 8-273 engine



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Fig. Fig. 11: Rolling the new front seal into position

 
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