A recent febi ProTip described the overheating problems that can indicate a broken water pump impeller. The problem can be seen on various Citroen, DS, Fiat, Ford, Jaguar, Lancia, Land Rover, Mitsubishi, Opel, Peugeot and Toyota models.

Problem
The engine coolant temperature and engine management warning lamps are illuminated. The fault code ‘P0115 coolant temperature malfunction’ is present in the engine ECU.

Cause
The original water pump impeller is made from plastic, which can become detached from the impeller shaft. Therefore, the water pump is turning with no effect and no coolant will flow around the cooling circuit of the engine.

Solution
Ensure the engine is cool, then remove the coolant filler cap. Remove the upper hose to the coolant expansion bottle and hold this over a suitable receptacle. Start the engine - with the engine at idle, there should be a small trickle of coolant flowing. The flow should increase as the engine speed increases. If there is no coolant flow, this would suggest the water pump impeller is not turning.

Remove the auxiliary belt and timing belt. Replace the defective water pump with febi water pump 39304, which has an improved water pump design with a metal impeller. This eliminates the potential failure caused by the water pump fitted with a plastic impeller. When replacing the faulty water pump, febi recommends that the timing belt kit and auxiliary drive belt is also replaced at the same time to ensure the reliability of the engine.

Fill the cooling system with fresh coolant, then vacuum bleed the system to expel all air from it.

To ensure the cooling system is working correctly, start the engine and recheck the flow of the coolant to the expansion bottle. Reset any fault codes stored in the engine ECU.