UK Car Repair Questions? Ask a Mechanic for Answers ASAP
Hi I'm Ross, thanks for trusting me to help you today. I am a diagnostic and repair technician and I look forward to working with you.This sounds like the temp sensor is at fault, however as this happens after 5 mins the thermostat operation should be checked. If you have not already done this, Start the car from cold and put the cabin heaters on full fan and heat. Allow the engine to warm up. If the blowers keep the gauge in "normal" position, it indicates a physical issue with the cooling system such as a blockage or sticking thermostat. If the blowers are warming up as normal and the temp gauge quickly goes to the top with no signs of overheating, I strongly suspect this is simply a faulty temp sensor.
The image attached shows the location of the sensor, it is a thread in sensor with a two pin connector, this is very simple to change.The engine MUST be cold, release the coolant bottle cap to release residual pressure, and refit the cap tightly.Use a ring spanner to loosen the old sensor, then simply unscrew it, coolant will begin to drain but shouldn't be much if the coolant cap is on so if you are quick, very little will be lost. Ensure the old washer is removed and thread in the new sensor and washer, tighten lightly with a spanner, reconnect the plug and top up coolant as required. Run engine and check for leaks.
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