T25,T4,G3 Thermostat O-Ring - Waterboxer Engines

This replacement O-ring seals the thermostat cover to the thermostat housing, preventing coolant leaks and helping the cooling system maintain the correct pressure. It fits Type 25 waterboxer petrol engines and a wide range of T4 5-cylinder petrol and diesel engines, plus selected VR6 applications and other later Volkswagen models using this 60mm x 3.5mm seal.

The O-ring sits between the thermostat cover and housing, compressing as the cover is tightened to create a watertight seal. If the seal becomes flattened, brittle or damaged, coolant can leak from the thermostat housing, often causing staining, coolant loss and overheating risk. Replacing the O-ring when changing the thermostat or removing the cover is good practice and helps ensure a reliable repair.

This seal is suitable for T25 waterboxer petrol models, T4 2.4 diesel, 2.5 petrol, 2.5 TDI and 2.8 VR6 models, and a range of VR6-equipped Golf, Vento, Passat and Sharan models. Always check the thermostat housing and cover for corrosion or distortion before fitting, and inspect the thermostat itself if the system is already dismantled.

Vehicle Fitment

Volkswagen T25 / T3 1983-1991
Waterboxer petrol models

Volkswagen T4 1990-2003
2.4 Diesel: AAB, AJA
2.5 Petrol: AAF, ACU, AEU, AEN, AET, APL, AVT
2.5 TDI: AJT, AYY, ACV, AUF, AYC, AXL, AXG
2.8 VR6: AES

Volkswagen California T4 1996-2003
2.4 Diesel, 2.5 Petrol, 2.5 TDI, 2.8 VR6

Volkswagen Golf Mk3 1992-1999
2.8 VR6, 2.9 VR6

Volkswagen Golf Mk4 1999-2002
2.8 VR6

Volkswagen Bora 1998-2005
2.8 VR6

Volkswagen Vento 1992-1998
2.8 VR6

Volkswagen Passat B3/B4 1991-1997
2.8 VR6, 2.9 VR6

Volkswagen Passat 3B / 3BG 1997-2005
2.5 TDI, 2.8 V6

Volkswagen Sharan Mk1 1995-2000
2.8 VR6

Product Details

• Inner diameter: 60mm
• Thickness: 3.5mm