Checking the thermostat valve (Audi 100 C3)

Thermostat valve (see fig. Air filter) controls the damper. If the valve is faulty, there may be interruptions in the engine operation at idle in the warm-up mode, interruptions when increasing the rotation speed, the engine develops insufficient power, and fuel consumption increases. The valve is checked on a cold engine. The damper should turn easily, without jamming. On a warm engine, depending on the ambient temperature, the access of warm air should be partially or completely blocked.

Execution order

1. Remove the filter without disconnecting hoses (5) and (17).

2. Start the engine and let it idle.

3. Disconnect the hose from the valve. The damper should block the supply of warm air.

4. Put a hose on the valve. The damper should open access to warm air.

5. Disconnect the hose. The flap should turn and block the access of warm air. If this does not happen, then the valve is faulty.

(Material republished from the website: «AudiManual.ru»)