AERA members have reported engine oil leaks at the rear of 1990-94 Ford 4.0L engines. This leak has often been misdiagnosed as a leaky rear main seal. The cause of this leak may be uneven mating surfaces on the rear main bearing cap.
The repair requires the oil pan to be removed and thoroughly cleaned of all sealer. The rear main bearing cap must also be removed and cleaned. After all parts are completely clean, they must also be wiped down with denatured alcohol to remove any remaining residue.
To correctly install the rear main bearing cap:
1. Apply small amounts of Loctite 515 sealer, or equivalent, to the cap
mating surfaces in the block.
2. Make sure the bearing insert is in place. Install the cap and finger tighten
new mounting bolts Part #F0TZ-6345-A & #E3TZ-6345-E.
3. Align the rear main cap so the rear main seal bore is concentric and
torque the new mounting bolts to 66-77 ft. lbs.
Care must be taken when installing the engine’s oil pan. After reattaching the oil pump and windage tray, follow the steps listed below:
1. Fill the cavities between the block and rear main cap for the wedge seal
with Loctite 515. Install the seal wiping any excess sealer from the area.
2. Place a 1/8″ bead of Loctite 598 sealer on the four corners of the oil pan
and install the revised (High Crush) oil pan gasket Part #F0TZ-6710-C
3. Place a 1/8″ bead of Loctite 598 sealer on both ends of the block joint
areas. Set the oil pan in place over the 4 studs and snug up the nuts.
4. Align the oil pan within .010″ (.25 mm) of rear block face and torque the pan bolts to 5-7 ft. lbs.
5. Install the rear main seal service Part #D7RZ-6701-A, using the revised
installation tool T95T-6701-A. The two previous design tools may cause
seal damage during installation.