Engine timing chain tensioner O-ring, 12 x 1.78mm. Porsche 911 84-89 / 964 Turbo 3.0L  ❭  99970169040

Engine timing chain tensioner O-ring
This O-Ring is an OE-style sealing ring designed for the engine timing chain tensioner assembly on Porsche 911 and 964 Turbo models. It provides a leak-proof seal between the hydraulic chain tensioner and engine housing. The O-ring measures approximately 12 x 1.78 mm.
Sold individually, 2 required per engine

Fits:
Porsche 911 1984 - 1989
Porsche 964 Turbo 3.3L 1990 - 1992 (Engine code: 3069)

Diagram ref no 11

Installed between the hydraulic chain tensioner and engine housing, the O-ring prevents engine oil leakage while maintaining proper hydraulic pressure within the timing chain tensioner system. Correct sealing is essential for reliable chain tension control and accurate engine valve timing. A compromised seal may result in oil leaks, pressure loss, or reduced tensioner performance.

This O-ring is ideal for preventative maintenance, engine rebuilds, timing chain service work, or replacement during tensioner overhaul procedures.

The O-ring seals the hydraulic timing chain tensioner assembly, preventing oil leakage and helping maintain proper hydraulic pressure within the timing system. This supports reliable timing chain operation and accurate engine valve timing.

Function
• Seals hydraulic timing chain tensioner assembly
• Prevents engine oil leakage around tensioner housing
• Maintains hydraulic pressure within timing system
• Supports accurate timing chain tension operation
• Resists heat, oil exposure, and pressure cycling

Over time, engine O-rings can harden, flatten, or crack due to heat exposure, oil contamination, and age. A failing tensioner seal may cause oil leaks and reduced hydraulic pressure, potentially affecting timing chain tension stability. Replacing worn O-rings during service helps maintain reliable engine lubrication and timing system operation.

When to replace
•  Oil leakage around timing chain tensioner
•  During timing chain or tensioner servicing
•  Hardened, flattened, or damaged O-ring seal
•  During engine rebuild or overhaul
•  Preventative maintenance on high-mileage engines

Related reference numbers
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99970169040

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