Type 25 Oil Filler Tube Gasket - Waterboxer Engines

This oil filler pipe base gasket fits between the oil filler tube and the crankcase on 1900cc and 2100cc petrol Waterboxer engines fitted to Type 25 / T3 buses. It is a critical sealing component that ensures the oil filler pipe is securely sealed to the engine case, preventing oil leaks and unwanted crankcase vapours escaping.

On Waterboxer engines, the oil filler tube bolts directly to the crankcase and relies on this gasket to create a proper oil-tight seal. Over time, the original gasket can harden, shrink, or break down due to heat and oil exposure. When this happens, oil seepage around the base of the filler pipe is common, often leaving oily residue around the engine and increasing the risk of fumes in the engine bay.

Replacing this gasket is strongly recommended whenever:

• The oil filler pipe is removed or replaced

• You are curing oil leaks around the filler tube

• Carrying out engine rebuilds or general resealing work

What this gasket does and how it works

The gasket sits directly between the flange of the oil filler pipe and the crankcase mating surface. When tightened, it compresses evenly to:

• Seal engine oil inside the crankcase

• Prevent oil mist and vapour escaping

• Maintain correct crankcase pressure

A good seal at this point is essential for clean engine operation and helps prevent oil leaks that can be mistaken for more serious crankcase or breather issues.

Fitment

• Vehicles: Type 25 / T3

• Years: 1983–1992

• Engines: 1900cc & 2100cc petrol Waterboxer

Fitting notes / related parts

• Always clean both mating surfaces before installation

• Do not reuse old or compressed gaskets

• Often replaced alongside the oil filler pipe and oil filler cap

• Lightly oiling the gasket before fitting can help ensure an even seal

This is a small but essential service item that plays a big role in keeping your Waterboxer engine clean, sealed, and leak-free.