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Thermostat Valve Inspection

Model: BMW Serie 5 E39 - Years: 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003
Part: Thermostat

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The thermostat valve is a device consisting of a self-regulating valve associated with a thermostat. The thermostat regulates the valve opening based on temperature.

In the engine's cooling circuit, the valve will open less at lower temperatures and more at higher temperatures: it will be completely closed (preventing fluid flow) for temperatures below the activation threshold and fully open (allowing full fluid flow) for temperatures considered optimal for the specific system.

One common cause of malfunction is blockage, usually caused by dirt or rust.

In the case of the vehicle in question, the thermostat valve is located inside the plastic housing where various hoses converge: once the hoses are disconnected and the mounting pins are removed, it is easy to extract the valve and assess its condition.


Updated on 10 February 2026 by ScegliAuto


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