A leaking rear main seal is a problem that many Mustang owners face, but are not always sure on how to make the repair. Since you do have to drop the transmission to replace a main seal, the task can be quite intimidating. Today, we here at LMR walk you through the steps on how to replace a rear main seal on a Coyote-powered S197, but the same procedure works on most modular Ford engines.
Parts List:
Tool List:
- Brake Clean & Towels
- Fresh Engine Oil
- RTV Silicone
- Compressed Air
- Vise
- Large Metal Disc (This is to install the rear main seal into the retainer plate.)
- Hammer
- Drift Set
- Regular Pry Bar Set
- Hook-and-Point Pry Bar Set
- Razor Blade or Gasket Scraping Tool
- Ratcheting Wrench Set
- 1/4" & 3/8" Socket Set
- 1/4" Torque Wrench
Installation Instructions
Step 1: Prepare for the Job
For Mustangs with an automatic transmission, take note of the shifter linkage and automatic transmission cooler lines. Ensure all transmission-related components are already removed from the vehicle.
Step 2: Remove the Crankshaft Sensor Ring
Locate and remove the crankshaft sensor ring (also called a pulse ring or exciter ring).
Step 3: Remove the Separator Plate/Electrical Components
- Disconnect the crankshaft position sensor electrical connection.
- Loosen the sensor hold-down bolt with an 8mm ratcheting wrench.
- Slide the sensor out of the retainer plate.
- If needed, remove the block plug and clean the area with brake cleaner and towels.
Step 4: Remove the Retainer Plate
- Loosen and remove the eight bolts securing the retainer plate (six on the engine block and two on the oil pan).
- Use a hook and point pry bar to separate the retainer plate from the engine block.
Step 5: Clean the Area
- Cover the oil pan with paper towels.
- Remove old silicone from the engine block with a razor blade.
- Clean the area with brake cleaner and towels.
Step 6: Clean and Inspect the Retainer Plate
- Clean the retainer plate and its retaining bolts.
- Brush the mating surface with a wire wheel and blow it with compressed air.
Step 7: Install the Rear Main Seal
- Place the retainer plate face down on a workbench.
- Align the new rear main seal by hand, ensuring it stays in place (gasket side facing you).
- Put a thin metal disc larger than the seal over it.
- Secure it in a large vise and close the vise to press the seal into place evenly, ensuring it's flush with the retainer plate's outside face.
- Verify that the Garter spring is in place.
Step 8: Lubricate the Seal
- Lubricate the seal lips with fresh engine oil or assembly grease.
- Wipe the mating surface on the retainer plate with a clean towel.
Step 9: Apply Silicone
- Apply an 1/8-inch bead of RTV silicone to the mating surfaces (inside of the bolt holes).
- Apply a 5/16-inch bead of silicone to both sides of the oil pan where it meets the engine block.
Step 10: Reinstall the Retainer Plate
- Position the retainer plate into place.
- Use a small flathead screwdriver to verify that the seal's lip doesn't roll inward.
- Hand-tighten all previously removed bolts.
- Evenly tighten the bolts to fully seat the retainer plate.
- Torque the bolts in a crisp cross pattern to 89 pound-inches first, then rotate an additional 45 degrees.
- Torque the oil pan bolts using the same specs.
Step 11: Reconnect Sensors and Components
- Reinstall the crankshaft position sensor.
- Torque the bolt to 89 pound-inches.
- Reconnect the electrical connection, ensuring it clicks.
- Reinstall the crankshaft sensor ring in the correct orientation (teeth facing the engine).
- Reinstall all transmission-related components.
Conclusion
That's it! You should now be able to successfully install a rear main seal in a Modular engine. If you are uncomfortable with this installation, we highly suggest seeking professional mechanical help. For everything, 1979-Present Mustang, keep it right here with the real Mustang enthusiasts, LMR.com.
