Ford Mustang/Capri 1979-1988 Repair Guide

Rear Main Oil Seal



Refer to the build dates listed below to determine if the engine is equipped with a split-type or one-piece rear main oil seal. Engines manufactured after the dates indicated have a one-piece oil seal, while those built prior to the indicated dates are equipped with a split-type seal.

4-140 - 9/28/81
6-232 - 4/1/83
8-302 - 12/1/82

Split-Type Seal

See Figure 1

The rear oil seal installed in these engines is a rubber type (split-lip) seal.

  1. Remove the oil pan and, if required, the oil pump.
  3. Loosen all the main bearing caps, allowing the crankshaft to lower slightly.

The crankshaft should not be allowed to drop more than1/32in. (0.8mm).

  1. Remove the rear main bearing cap and remove the seal from the cap and block. Be very careful not to scratch the sealing surface. Remove the old seal retaining pin from the cap, if equipped. It is not used with the replacement seal.
  3. Carefully clean the seal grooves in the cap and block with solvent.
  5. Soak the new seal halves in clean engine oil.
  7. Install the upper half of the seal in the block with the undercut side of the seal toward the front of the engine. Slide the seal around the crankshaft journal until 3 / 8 in. (9.5mm) protrudes beyond the base of the block.
  9. Tighten all the main bearing caps (except the rear main bearing) to specifications.
  11. Install the lower seal into the rear cap, with the undercut side facing the front of the engine. Allow 3 / 8 in. (9.5mm) of the seal to protrude above the surface, at the opposite end from the block seal.
  13. Squeeze a 1 / 16 in. (1.6mm) bead of silicone sealant onto the areas shown.
  15. Install the rear cap and torque to specification.
  17. Install the oil pump, if applicable, and the oil pan. Fill the crankcase with oil, start the engine, and check for leaks.

Click image to see an enlarged view

Fig. Fig. 1: Split-type rear main oil seal installation

One-Piece Seal

See Figure 2

  1. Remove the transmission, clutch, and flywheel or driveplate, after referring to the appropriate section for instructions.
  3. Punch two holes in the crankshaft rear oil seal on opposite sides of the crankshaft, just above the bearing cap to the cylinder block split line. Install a sheet metal screw in each of the holes or use a small slide hammer, and pry the crankshaft rear main oil seal from the block.

Use extreme caution not to scratch the crankshaft oil seal surface.

  1. Clean the oil seal recess in the cylinder block and main bearing cap.
  3. Coat the seal and all of the seal mounting surfaces with oil and install the seal in the recess, driving it into place with an oil seal installation tool or a large socket.
  5. Install the driveplate or flywheel, clutch and transmission in the reverse order of removal.

Click image to see an enlarged view

Fig. Fig. 2: One-piece rear main oil seal installation