N90316801 – Coolant Temperature Sensor O-Ring for VW Golf Mk4 Mk5, Audi A4 B6 B7 | YDU

Description

A failed or deteriorated coolant temperature sensor O-ring commonly presents as a visible coolant leak around the sensor, a coolant smell after driving, or an unexplained drop in coolant level. This small rubber O-ring seals the coolant temperature sensor into the coolant housing or thermostat housing, preventing coolant loss and ensuring accurate sensor readings. It is recommended to replace this O-ring any time the coolant temperature sensor is removed or replaced, as reusing the old O-ring risks immediate leakage. Lightly lubricate the O-ring with clean coolant before fitting to ease installation and avoid twisting. Torque the coolant temperature sensor to approximately 15–20 Nm; always verify the correct torque specification for your specific engine variant using a workshop manual. Allow the engine to cool completely before beginning work to prevent burns from pressurised coolant. After fitting, top up the coolant to the correct level, run the engine to operating temperature, and inspect the sensor area carefully for any signs of leakage.