Crankshaft – Rear Oil Seal Replacement

Overview

This procedure replaces the rear oil seal (commonly called the rear main seal) on the Porsche 944 S2 with its 3.0L engine. The rear oil seal prevents oil from leaking out of the engine where the crankshaft exits the block to connect to the flywheel. A leaking seal can contaminate the clutch, reduce oil levels, and damage components, so replacing it is critical for engine health. This guide is tailored for DIY enthusiasts with mechanical experience, walking you through removing the transaxle, clutch, and flywheel to access and replace the seal.

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Tools Required

• 10mm (3/8 inch) wrench
• 13mm wrench
• 17mm wrench
• 8mm triple square driver
• Torx T55 bit
• Socket set (metric, including 13mm, 17mm, and 19mm)
• Torque wrench
• Jack and jack stands
• Flywheel lock tool (Porsche tool P9206 or equivalent)
• Seal puller or flathead screwdriver
• PVC pipe or seal driver (matching seal diameter, approx. 90mm)
• Shop rags and degreaser

Parts Required

• Rear oil seal – 999 113 426 41
• Flywheel bolts (single-use) – 944 102 235 00 (qty: 8)
• Clutch pressure plate bolts (recommended replacement) – 944 116 027 01 (qty: 6)

Required Additional Procedures

Steps in these procedures are required to complete this process:

• Transaxle Removal
• Clutch Removal
• Engine Oil Change

Step-by-Step Procedure

Step 1: Prepare the Vehicle

1. Park the car on a flat surface and disconnect the negative battery terminal using a 10mm (3/8 inch) wrench.
2. Safely raise the rear of the vehicle using a jack and secure it with jack stands. Ensure it’s stable before proceeding.
3. Drain the engine oil to avoid spills during the procedure. Follow this link to ensure this step – Engine Oil and Filter Replacement – of the process is followed accurately.

Step 2: Remove the Transaxle

4. Follow this link to ensure this step – Transaxle Removal – of the process is followed accurately. This involves disconnecting the axles, shift linkage, and transaxle mounts, then lowering the transaxle from the vehicle.
5. With the transaxle removed, you’ll have access to the clutch assembly and flywheel at the rear of the 3.0L engine.

Step 3: Remove the Clutch and Flywheel

6. Follow this link to ensure this step – Clutch Removal – of the process is followed accurately. Remove the pressure plate bolts (6 x 8mm triple square) and clutch disc.
7. Use a flywheel lock tool (P9206 or equivalent) to hold the flywheel in place. Remove the 8 flywheel bolts using a Torx T55 bit. These are single-use bolts; discard them.
8. Carefully lift the flywheel off the crankshaft. The rear oil seal is now visible behind it, seated in the engine block.

Step 4: Remove the Old Rear Oil Seal

9. Locate the rear oil seal (999 113 426 41) in the engine block. It’s a rubber and metal ring around the crankshaft.
10. Use a seal puller or carefully insert a flathead screwdriver into the notch on the seal’s outer edge. Gently pry it out, working around the perimeter to avoid scratching the crankshaft or block.
11. Clean the seal seating area with degreaser and a rag to remove oil residue and debris.

Step 5: Install the New Rear Oil Seal

12. Inspect the new seal (999 113 426 41). Ensure the lip side (with the spring) faces inward toward the engine and the flat side faces outward.
13. Lightly coat the crankshaft with engine oil where the seal will contact it. Avoid oil on the outer edge of the seal or block to ensure a clean fit.
14. Position the seal over the crankshaft and use a PVC pipe or seal driver (approx. 90mm diameter) to tap it evenly into place. Work slowly around the edge until it’s flush with the block.

Step 6: Reassemble the Flywheel and Clutch

15. Reinstall the flywheel onto the crankshaft. Use new flywheel bolts (944 102 235 00) and torque them to 90 Nm (66 ft-lbs) in a crisscross pattern using a torque wrench.
16. Reinstall the clutch disc and pressure plate. Use new pressure plate bolts (944 116 027 01) if replacing, and torque to 25 Nm (18 ft-lbs).
17. Double-check alignment using a clutch alignment tool if needed (specific to the S2’s 3.0L setup).

Step 7: Reinstall the Transaxle

18. Follow the reverse of the Transaxle Removal procedure to reinstall the transaxle, ensuring all mounts are torqued to 40 Nm (30 ft-lbs) for the S2’s specific bolts.
19. Reconnect the axles, shift linkage, and any electrical connectors removed earlier.

Step 8: Finalize and Test

20. Refill the engine with oil as per the Engine Oil and Filter Replacement procedure.
21. Lower the vehicle, reconnect the battery, and start the engine. Let it idle for 5-10 minutes to check for leaks.

Post Procedure Checklist

• Check for oil leaks around the rear of the engine and under the car after running for 5 miles (8 km).
• Verify clutch operation by shifting through gears (engine off, then on).
• Ensure no unusual noises come from the flywheel or transaxle area.
• Recheck engine oil level after a short drive of 5 miles (8 km).

Sources

• Clark’s Garage
• Pelican Parts
• Porsche 944 Workshop Manual, Volume 1
• Youtube