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Peter Zavarelli
Peter Zavarelli,
Category: UK Car
Satisfied Customers: 29116
Experience:  Technical Consultant at Just Answer
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Customer Question

On longer journeys the temp gauge will occasionally quickly rise from normal into the red zone and after a few moments quickly return to normal. Very occasionally it will also activate the dashboard overheat warning light but this is very rare. the erratic readings appear at random and the last time it happened was twice on a 100 mile journey. The car never appears to be hot or overheating when you open the bonnet to look, it is not using any water there are no leaks. The radiator has been back flushed and brand new coolant and antifreeze added. If it is dodgy cylinder head or radiator fan sensor will plugging it in to a fault code reader identify any faulty sensors. Could it be a very small leak from the head gasket that allows a small gas pocket to form and cause a high temp reading before the gas pocket is flushed out the system by the water flow?? I assume the system will not over pressurise if this is the case as the expansion resevior cap has a spring loaded safety vale
Submitted: 1 year ago.
Category: UK Car
Expert:  Peter Zavarelli replied 1 year ago.

Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.My info is somewhat limited on your model here but I had seen no one else has responded and would like to see if I can help here.If at any time you feel that I cannot help with this please let me know.

If the engine does not appear to be over heating at all with this issue here when it occurs and this occurs randomly this can be a fault with a faulty engine coolant temp sensor needing replaced.I have seen the engine coolant temp sensor fail in the past before causing intermittent issues like this here.Having a code reader/scan tool plugged into your vehicle to read out fault codes will help identify if this is the cause here for sure if a code has set for this issue.It may display a fault for the engine coolant temp sensor which will help identify that it is the cause here.

It is possible a cylinder head gasket leak is the cause as well but usually this would occur all of the time if this was the case.

I would have the fault codes checked first and engine coolant temp sensor tested.If a fault is found with it then it will need replaced but if this all checks out o.k. then I would have a block test done to see if a head gasket is an issue here.Most shops can do the block test in less then an hours time to see if there is a leaking head gasket issue.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete