Type 25 Water Header Tank - Waterboxer And Diesel Engines

This non-pressurised coolant expansion (header) tank is a direct replacement for the original upper coolant reservoir fitted behind the rear number plate on Volkswagen Type 25 (T25 / T3) and Vanagon models. Suitable for both petrol and diesel engines, it plays a key role in managing coolant expansion and maintaining correct system levels.

Unlike the pressurised expansion tank in the engine bay, this rear-mounted tank acts as an overflow and recovery reservoir. As coolant heats up and expands, excess coolant is directed into this tank. When the system cools, coolant is drawn back, ensuring consistent coolant levels and preventing air from entering the cooling system. A cracked, discoloured, or leaking tank can allow coolant loss and air ingress, leading to overheating and poor cooling performance.

Manufactured to match the original factory shape and mounting points, this replacement tank fits neatly behind the number plate with no modification required. It is ideal for replacing ageing original tanks that have become brittle over time due to heat and UV exposure.

How it works

This tank collects excess coolant expelled from the cooling system during normal heat expansion. As temperatures drop, coolant is siphoned back into the system, maintaining correct levels and helping protect the engine from overheating or air locks.

Fitment & installation notes

• Non-pressurised upper/header tank

• Mounts behind the rear number plate

• Suitable for petrol and diesel T25 / Vanagon models

• Direct replacement using existing fixings and hoses

• Uses non-pressurised cap – part number: 025121482

This tank is often replaced during cooling system refreshes, radiator work, or when diagnosing coolant loss issues.

Engine compatibility

• DF – 1.9 Waterboxer (08/85–07/87)

• DG – 1.9 Waterboxer (08/85–07/89)

• DH – 1.9 Waterboxer (01/83–07/85)

• GW – 1.9 Waterboxer (08/83–07/85)

• CS – 1.6 Diesel (08/82–07/85)

• JX – 1.6 Turbo Diesel (08/87–07/92)