GM Cutlass RWD 1970-1987 Repair Guide

Rear Main Oil Seal

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REMOVAL & INSTALLATION



See Figures 1, 2, 3 and 4

L-6 Engine

The rear main bearing oil seal is of molded design, and both halves can be replaced without removal of the crankshaft.

  1. Remove the oil pan and the oil pump.
  2.  
  3. Remove the rear main bearing cap.
  4.  
  5. Remove the oil seal from the groove by lifting the end tab, then clean the seal groove.
  6.  
  7. Lubricate the lip and outside diameter of the new seal with engine oil. Keep oil off the parting line surface.
  8.  
  9. Insert the new seal into the cap and roll it into place with your fingers. Use only light pressure on the seal to avoid cutting the outside diameter of the seal with the sharp edges of the groove. make sure the tabs of the seal are properly located in the cross grooves.
  10.  
  11. To remove the upper half of the seal, tap one end of the seal with a brass punch until the other end protrudes far enough to be grasped with a pair of pliers.
  12.  
  13. Lubricate the lip and outside diameter of a new seal with engine oil. Roll the new seal into place by gradually pushing with a hammer handle while turning the crankshaft.
  14.  
  15. Install the rear main cap. Install the oil pan.
  16.  

Buick Built Engines
LOWER HALF
  1. Remove the oil pan and rear main bearing cap.
  2.  
  3. Remove the old seal from the bearing cap and place a new seal in the groove with both ends projecting above the parting surface of the cap.
  4.  



Click image to see an enlarged view

Fig. Fig. 1: Installing rear bearing cap oil seals - Buick built engines



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Fig. Fig. 2: Apply a small amount of sealer to the split line - Buick built engines

  1. Force the seal into the groove by rubbing down with a hammer handle or smooth tool, until the seal projects above the groove not more than 1 / 16 in. Cut the end off flush with the surface of the cap. Use a razor blade.
  2.  
  3. On the 231, 252, and 350, place new neoprene seals in the grooves in the sides of the bearing cap after soaking the seals in kerosene for a minute or two.
  4.  
  5. To install, reverse the above. Use a small amount of sealer on the bearing cap mating surface. The engine must be operated at low rpm when first started, after a new seal is installed.
  6.  

UPPER HALF

Although the factory recommends removing the crankshaft to replace the top half of the oil seal, the following procedure can be used without removing the crankshaft.

  1. Remove the oil pan and rear main bearing cap.
  2.  
  3. Loosen the rest of the crankshaft main bearings and allow the crankshaft to drop about 1 / 16 in.
  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 1 / 2 in. on the end. Generously lubricate the new seal with 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 if 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 specifications. Make sure there is no oil on the parting surfaces.
  14.  
  15. Replace the oil pan. Run the engine slowly for the first few minutes of operation.
  16.  

V8 Chevrolet Built Engines

The rear main bearing seal may be replaced without removing the crankshaft. Seals should only be replaced as a pair. The seal lips should face the front of the engine when properly installed.

  1. Remove the oil pan, and pump as previously outlined, and remove the rear main bearing cap.
  2.  
  3. Pry the lower seal out of the bearing cap with a screwdriver, being careful not to gouge the cap surface.
  4.  
  5. Remove the upper seal by lightly tapping on one end with a brass pin punch until the other end can be grasped and pulled out with pliers.
  6.  



Click image to see an enlarged view

Fig. Fig. 3: Fabricate an oil seal tool - Chevrolet and Oldsmobile built engines



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Fig. Fig. 4: Removing the upper half of the oil seal - Chevrolet and Oldsmobile built engines

  1. Clean the bearing cap, cylinder block, and crankshaft mating surfaces with solvent. Inspect all these surfaces for gouges, nicks, and burrs.
  2.  
  3. Apply light engine oil on the seal lips and bead, but keep the seal ends clean.
  4.  
  5. Insert the top of the installation tool between the crankshaft and the seal of the cylinder block. Place the seal between the tip of the tool and the crankshaft, so that the bead contacts the tip of the tool.
  6.  
  7. Be sure that the seal lip is facing the front of the engine, and work the seal around the crankshaft using the installation tool to protect the seal from the corner of the cylinder block.
  8.  

Do not remove the tool until the opposite end of the seal is flush with the cylinder block surface.

  1. Remove the installation tool, being careful not to pull the seal out at the same time.
  2.  
  3. Using the same procedure, install the lower seal into the bearing cap. Use you finger and thumb to lever the seal into the cap.
  4.  
  5. Apply sealer to the cylinder block only where the cap mates to the surface. Do not apply sealer to the seal ends.
  6.  
  7. Install the rear cap and torque the bolt to specifications. Install the oil pan and pump as previously described.
  8.  

V8 Oldsmobile Built Engines

The crankshaft need not be removed to replace the rear main bearing upper oil seal.

  1. Drain the crankcase and remove the oil pan and rear main bearing cap.
  2.  
  3. Using a blunt-ended tool, drive the upper seal into its groove on each side until it is tightly packed. This is usually 1 / 4 - 3 / 4 in.
  4.  
  5. Cut pieces of new seal 1 / 16 in. longer than required to fill the grooves and install, packing into place.
  6.  
  7. Carefully trim any protruding seal, being sure not to scratch or damage the bearing surface.
  8.  
  9. Install a new seal in the bearing cap and install cap, tightening bolts to 120 ft. lbs. (162 Nm), 107 ft. lbs. (145 Nm), on V6 diesel. Install the oil pan.
  10.  

 
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