Crankshaft Main Bearing O-Ring, 51x 4.5. Porsche 911 78-89 / 964 / 993 / 996 Turbo / 997 Turbo / GT3  ❭  99970728541

Crankshaft Main Bearing O-Ring, 51x 4.5
This OE Match crankshaft main bearing O-ring is a replacement sealing ring for Porsche 911 1978–1989, 964, 993, 996 Turbo, 997 Turbo, and GT3 models. Measuring 51 x 4.5, it is designed to match the original-style fitment and sealing function within the crankshaft / main bearing area.
Sold individually

Fits:
Porsche 911 1978 - 1989
Porsche 964 1989 - 1994
Porsche 993 1995 - 1998
Porsche 996 Turbo 3.6L 2001 - 2005
Porsche 996 GT3 3.6L 1999 - 2005
Porsche 997.1 Turbo 3.6L 2007 - 2009
Porsche 997.2 Turbo 3.6L 2010 - 2013
Porsche 997 GT3 3.6L / 3.8L / 4.0L 2007 - 2011

Diagram ref no 21

The crankshaft main bearing O-ring helps seal the relevant bearing or housing connection to prevent oil leakage and maintain correct engine oil sealing. A properly sealing O-ring is essential for protecting engine components and maintaining oil system integrity.

What This Part Does / Functions
•  Replaces the crankshaft main bearing
•  O-ring Helps seal the crankshaft / main bearing housing area
•  Supports correct engine oil sealing
•  Helps prevent oil leaks from aged or flattened seals
•  Suitable for engine rebuild, crankshaft, or bearing service
•  Replaces hardened, cracked, flattened, swollen, or damaged O-rings
•  OE Match replacement for Porsche engine sealing repair.

Why Replace This Part?
O-rings can harden, flatten, crack, swell, or lose sealing ability due to heat, age, oil exposure, pressure, and engine service work. A worn or damaged crankshaft main bearing O-ring may allow oil seepage or leakage, affecting engine cleanliness and oil system reliability. Replacement is recommended whenever the related engine components are removed or when oil leakage is present.

When to Replace This Part
•  Engine rebuild or major engine service is being carried out
•  Crankshaft or main bearing components are being serviced
•  Oil leakage is present around the related sealing area
•  The original O-ring is hardened, flattened, cracked, or damaged
•  Bearing housing or crankshaft sealing components have been removed
•  Preventative replacement is required during engine assembly
•  The vehicle is undergoing Porsche engine restoration

Where it fits on the car
This O-ring fits within the engine crankshaft / main bearing sealing area. Exact position can vary depending on engine type and model-specific crankcase layout.


Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99970728541

The product you are viewing cross references to these numbers