Water pump thermostat. Porsche 981/982 Boxster / 981C/982C Cayman / 991

The engine coolant thermostat is a small but essential component that regulates coolant flow through your engine. When the engine is cold, the thermostat remains closed to restrict coolant circulation, allowing the engine to reach its optimal operating temperature more quickly. Once the desired temperature is achieved, it opens to maintain consistent cooling and prevent overheating.   Products ref no. 9A712111000 which supersedes from old part numbers 9A110622602 & 9A110622603

Installation Tip: Always position the thermostat’s jiggle pin (bleed valve) at the 12 o’clock position when possible, to ensure proper air bleeding.

Thermostat Temperature Ratings

Many vehicles offer thermostats with different temperature ratings. These ratings indicate the temperature at which the thermostat begins to open.

Common Thermostat Failures

Thermostat Stuck Open (Most Common) The thermostat fails to close, causing continuous coolant flow even when the engine is cold. This prevents the engine from reaching normal operating temperature, often leading to poor fuel economy, rich air-fuel mixtures, and potential catalytic converter damage. Thermostat Stuck Closed The thermostat fails to open, restricting coolant flow through the engine. This results in overheating and may cause severe or even catastrophic engine damage.

Signs of a Failing Engine Coolant Thermostat

Engine overheating Engine not reaching optimal operating temperature Radiator fan not engaging properly       

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Diagram ref no 20