Chevrolet Full Size Cars 1979-1989

Rear Main Oil Seal

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REMOVAL & INSTALLATION



Chevrolet V6 and V8 Gasoline Engines
TWO PIECE SEAL


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Fig. Fig. 1 Dimensions for making an oil seal installation tool



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Fig. Fig. 2 Removing the lower rear main seal from the bearing cap



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Fig. Fig. 3 Removing the upper rear main seal



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Fig. Fig. 4 Packing the rear main oil seal

A 2-piece can be found on most Chevrolet produced gasoline engine through 1985. Most 1986 and later Chevrolet engines are equipped with a later design 1-piece seal.

  1. Remove the oil pan from the engine. For details, refer to the oil pan procedures earlier in this section.
  2.  
  3. Remove the oil pump and the rear main bearing cap.
  4.  
  5. Using a small pry bar, carefully pry the lower half of the oil seal from the rear main bearing cap.
  6.  
  7. Using a small hammer and a brass pin punch, drive the top half of the oil seal from the rear main bearing. Drive it out far enough, so it may be removed with a pair of pliers.
  8.  
  9. Using a non-abrasive cleaner, clean the rear main bearing cap and the crankshaft.
  10.  

BTo install:
  1. Fabricate an oil seal installation tool from 0.004 in. shim stock, shape the end to 1 / 2 in. long by 11 / 64 in. wide.
  2.  
  3. Coat the new oil seal with engine oil; DO NOT coat the ends of the seal.
  4.  
  5. Position the fabricated tool between the crankshaft and the seal seat in the cylinder case.
  6.  
  7. Position the new half seal between the crankshaft and the top of the tool, so that the seal bead contacts the tip of the tool.
  8.  

Make sure that the seal lip is positioned toward the front of the engine.

  1. Using the fabricated tool as a shoe horn, to protect the seal's bead from the sharp edge of the seal seat surface in the cylinder case, roll the seal around the crankshaft. When the seal's ends are flush with the engine block, remove the installation tool.
  2.  
  3. Using the same manner of installation, install the lower half of the seal onto the lower half of the rear main bearing cap.
  4.  
  5. Apply sealant to the cap-to-case mating surfaces and install the lower rear main bearing half to the engine; keep the sealant off of the seal's mating line.
  6.  
  7. Install the rear main bearing cap bolts. Using a lead hammer, tap the crankshaft forward and rearward, to line up the thrust surfaces. Torque the main bearing bolts to specification.
  8.  
  9. If not done already, install the oil pump
  10.  
  11. Install the oil pan and properly refill the engine crankcase.
  12.  

ONE PIECE SEAL


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Fig. Fig. 5 Carefully pry the seal from the retainer at these locations



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Fig. Fig. 6 One piece seal installation tool

A 2-piece can be found on most Chevrolet produced gasoline engine through 1985. Most 1986 and later Chevrolet engines are equipped with a later design 1-piece seal.

  1. Remove the transmission assembly from the vehicle. Refer to of this guide for removal procedures.
  2.  
  3. Remove the flywheel from the engine.
  4.  
  5. Using the notches provided in the rear seal retainer, carefully pry out the seal using a small tool.
  6.  

Extreme care should be taken when removing the seal so as not to nick and damage the crankshaft sealing surface.

To install:

  1. Before installation lubricate the new seal with clean engine oil.
  2.  
  3. Install the seal on J-3561 or an equivalent seal installation tool. Thread the tool into the rear of the crankshaft and tighten the screws snugly, this is to insure that the seal will be installed squarely over the crankshaft. With the tool properly positioned, tighten the tool wing nut until it bottoms.
  4.  
  5. Remove the tool from the crankshaft.
  6.  
  7. Install the flywheel to the engine.
  8.  
  9. Install the transmission assembly to the vehicle.
  10.  

ONE PIECE SEAL RETAINER AND GASKET

A 2-piece can be found on most Chevrolet produced gasoline engine through 1985. Most 1986 and later Chevrolet engines are equipped with a later design 1-piece seal. On these later vehicles equipped with the 1-piece seal, a rear seal retainer housing is mounted to the rear of the engine block. If necessary, the housing and gasket may be removed for service or replacement.

  1. Remove the transmission assembly from the vehicle. Refer to of this guide for removal procedures.
  2.  
  3. Remove the oil pan bolts, then lower the oil pan from the engine.
  4.  
  5. Remove the retainer and seal assembly.
  6.  
  7. Remove the gasket and seal from the retainer assembly.
  8.  

Whenever the retainer is removed a new retainer gasket and rear main seal must be installed.

To install:

  1. Thoroughly clean the gasket mating surfaces.
  2.  
  3. Position a new gasket, then install and secure the seal retainer.
  4.  
  5. Install the oil pan and tighten the retainers.
  6.  
  7. Install a new one piece seal to the retainer using a suitable installation tool.
  8.  
  9. Install the transmission assembly to the vehicle.
  10.  

Buick 231 V6 Engine


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Fig. Fig. 7 The new lower seal may be rolled into position



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Fig. Fig. 8 DO NOT over-apply sealant to the lower main bearing cap 231 V6

On this engine, there are 2 rear main seals. Fabric seals are pressed into the grooves formed in the crankcase and rear bearing cap, to the rear of the oil collecting groove. The fabric seals protect against leakage of oil around the crankshaft. Neoprene composition seals are placed in the grooves to the sides of the bearing cap and seal against leakage in the joints between the cap and crankcase. The neoprene seals are slightly longer than the grooves in the bearing cap but must NOT be cut to length.

When replacing the rear main seals, the upper half of the fabric seal may be repaired, but not replaced, with the crankshaft installed in the block. To completely replace the seal, the crankshaft must be removed. The lower part of the seal and the neoprene seals may be replaced in the conventional manner when the bearing cap is removed.

Place the new bearing cap neoprene seals (not the fabric seals) in kerosene for two minutes before installing them. The neoprene seals will swell up once exposed to the oil and heat when in the engine. It is normal for the seals to leak for a short time, until they become properly seated. The neoprene seals must NOT be cut to fit.

  1. Remove the oil pan and the rear main bearing cap.
  2.  
  3. In order to repair the upper fabric seal, use a blunt-edged tool to drive the upper seal into its grooves (on either side) until it is tightly packed. This is usually a distance of 1 / 4 - 3 / 4 in.
  4.  
  5. Measure the distance the upper seal was packed upward on either side, then cut pieces of the old lower fabric seal 1 / 16 in. longer than required to fill the grooves and install them, packing them into place.
  6.  

The lower main bearing cap may be used a holding fixture when trimming pieces of the old fabric seal which are to be used to repair the upper half of the seal.

  1. Install the new fabric seal into position in the bearing cap. A small wooden dowel may be used to carefully roll and pack the seal into position. Carefully trim any protruding edges of the new lower fabric seal. Do NOT cut the neoprene seals on the outside of the bearing cap.
  2.  
  3. Remove the old neoprene seals from the bearing cap, then remove the new neoprene seals from the solution and install them to the outer grooves.
  4.  

To help eliminate oil leakage at the joint where the cap meets the crankcase, apply RTV type sealer to the rear main bearing cap split line. When applying sealer, use only a thin coat as an over abundance will not allow the cap to seat properly.

  1. Reinstall the cap and the oil pan.
  2.  

Diesel and Oldsmobile 307 V8 Engines


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Fig. Fig. 9 Packing the rear main oil seal



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Fig. Fig. 10 Use the bearing cap as a holding fixture when cutting off lengths of the old seal

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, then remove the rear main bearing cap.
  2.  
  3. Using a special main seal tool or a tool that can be made from a dowel, 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. Measure the amount the seal was driven up on one side; add 1 / 16 in and 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. 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 the protruding seal.
  6.  
  7. Work these two pieces of seal up into the cylinder block on each side with two nail sets 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. Do not scratch the bearing surfaces with the razor.
  8.  
  9. Install a new seal in the rear main bearing cap. Run a 1 / 16 in. bead of sealer onto the outer mating surface of the bearing cap. Install the cap to the block and torque to specification.
  10.  
  11. Install the oil pan and properly refill the crankcase with clean engine oil.
  12.  

 
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