Type 25 Water Header Tank Cap - Waterboxer and Diesel Engines

This replacement reservoir tank cap is designed for the non-pressurised header tank fitted behind the rear number plate on Volkswagen Type 25 / T3 buses. It is a direct replacement screw-fit cap suitable for both petrol Waterboxer and diesel models from 1983 to 1992.

Unlike the pressurised expansion tank cap in the engine bay, this cap is used on the non-pressurised overflow/header tank at the rear of the vehicle. Its role is to securely seal the tank while allowing the cooling system to safely expand and contract without building pressure at this point. A damaged, loose, or missing cap can allow coolant to escape or contamination to enter the system.

Manufactured to original-style specifications, this replacement cap ensures a correct fit on the front reservoir tank and is ideal when renewing the header tank, servicing the cooling system, or replacing a lost or damaged original cap.

How it works

As coolant heats up, excess coolant is pushed into the non-pressurised header tank behind the number plate. This cap seals the tank while allowing coolant recovery as the system cools, helping maintain correct coolant levels and preventing air from entering the cooling system.

Fitment & installation notes

• Non-pressurised screw-on cap

• Fits front header / reservoir tank behind number plate

• Suitable for petrol and diesel T25 / T3 models

• Direct replacement with no modification required

• Not suitable for pressurised engine bay expansion tanks

This cap is a simple but essential component for maintaining a correctly functioning cooling system.

Engine compatibility

Petrol – Waterboxer:

• DF 1.9

• DG 1.9

• DH 1.9

• EY 1.9

• GW 1.9

• SP 1.9

• MV 2.1

• DJ 2.1

• SR 2.1

• SS 2.1

Diesel:

• CS 1.6 diesel

• JX 1.6 turbo diesel

• KY 1.7 diesel