1. Principle

• Function: Prevents engine oil leakage from the rear of the crankshaft (where it exits the engine block).

• Design:

  • Double-lipped fluoroelastomer (FKM) seal for superior heat/oil resistance.

  • Spring-loaded inner lip maintains constant pressure against the crankshaft.

  • Metal outer casing ensures a tight press-fit into the engine block or rear main housing.

2. Purpose

• Critical for:

  • Maintaining proper engine oil pressure.

  • Preventing oil contamination of the clutch/flywheel (in manual transmissions).

  • Avoiding oil leaks that could damage the transmission or exhaust components.

• Common Symptoms of Failure:

  • Oil leaks near the transmission bellhousing.

  • Burning oil smell (if leaking onto hot exhaust).

  • Low oil level warnings without visible top-end leaks.

3. Installation Method

Tools Required:

• Crankshaft locking tool (BMW-specific, e.g., BMW 11 2 300).

• Seal driver kit (appropriate size for the seal diameter).

• Clean lint-free rags and oil-compatible sealant (if specified).

Step-by-Step:

1. Access the Seal:

   • Remove transmission, clutch/flywheel (if manual), or flexplate (if automatic).

   • Clean the crankshaft flange and seal housing thoroughly.

2. Remove Old Seal:

   • Use a seal puller or pry tool (avoid scratching the crankshaft or bore).

3. Install New Seal:

   • Lightly lubricate the seal lip with clean engine oil.

   • Align the seal squarely and drive it in evenly with a seal driver (hammer blows must be centered to prevent distortion).

   • Ensure the seal seats fully against the housing shoulder.

4. Reassembly:

   • Reinstall flywheel/clutch or flexplate with proper torque specs.

   • Refill engine oil if drained.

Torque Specifications (Example):

• Flywheel bolts: 60 Nm + 90° turn (varies by model).

• Crankshaft pulley bolt: Replace (one-time-use, typically 100 Nm + 180°).

Key Notes:

⚠ Critical Tips:

• Never reuse an old seal or install it dry (lubricate the lip!).

• Misalignment during installation causes immediate leaks.

• BMW engines often require timing tools to lock the crankshaft during seal replacement.

Vehicle Compatibility Table