Type 25 Thermostat Housing Flange - 1983-84 - 1900cc Waterboxer Engines (DG Engine Codes)

This replacement plastic thermostat housing flange fits VW Type 25 buses equipped with 1900cc petrol Waterboxer engines using engine code DG, covering vehicles produced from August 1982 to July 1984. It is the early-style flange that attaches directly to the thermostat housing and provides the hose connection points required by the early cooling layout.

On early Waterboxer engines, this flange is a critical sealing and junction component. It locates the thermostat housing interface and routes coolant to the surrounding hoses. Over time, original plastic flanges can become brittle, warped, or cracked due to heat cycling and age, leading to coolant leaks, poor bleeding, and unstable operating temperatures. Replacing the flange restores proper sealing and correct hose alignment.

What this part does and how it works

The flange bolts to the thermostat housing and forms a sealed interface for coolant flow. Coolant passes through the flange as the thermostat opens and closes, directing flow to the radiator and engine circuits. A sound flange ensures:

• Leak-free sealing at the thermostat housing

• Correct hose routing and alignment

• Stable coolant circulation and temperature control

Fitment

• Vehicle: VW Type 25

• Years: 08/1982 – 07/1984

• Engine: 1900cc petrol Waterboxer

• Engine code: DG

• Application: Thermostat housing plastic flange (early type)

Note: This flange is for early engines up to 1985 and is not interchangeable with later thermostat housing/flange designs.

Fitting notes / related parts

• Inspect the thermostat housing for corrosion or distortion before fitting

• Always use new seals/O-rings as applicable when refitting

• Check all connected hoses and renew if hardened or cracked

• Refill with the correct coolant and bleed the system thoroughly after installation

A small but essential cooling component that helps keep early 1.9 Waterboxer Type 25 engines sealed, easy to bleed, and operating at the correct temperature.