Author Topic: Over cooling after 40 mph. Good below that speed.  (Read 329 times)

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Offline smartmart

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Over cooling after 40 mph. Good below that speed.
« on: September 04, 2017, 06:38:02 pm »
Driving in town is fine, everything works as normal.
Drive a bit faster, 40+ mph, the temperature gauge drops. Slow down, it returns to normal.
Any ideas?
Firstly, I was going to change the temperature sensor as they only cost £10.

Offline apav

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Re: Over cooling after 40 mph. Good below that speed.
« Reply #1 on: September 05, 2017, 08:44:46 am »
The sensor works up and down, so it should be OK. It sounds like your thermostat is stack open and the coolant circulates all the time. So when you are driving in the city and idling for long periods without moving, it warms up, but when you start moving, the temperature drops.

Offline stevem100

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Re: Over cooling after 40 mph. Good below that speed.
« Reply #2 on: September 05, 2017, 12:08:33 pm »
Yep all the symptoms point to thermostat stuck open. GO for that first.
Cheers Steve  8)

Offline smartmart

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Re: Over cooling after 40 mph. Good below that speed.
« Reply #3 on: September 06, 2017, 10:50:12 am »
Thank you. Both the Mazda main dealer (RRG) and Halfords Garage services have failed to find the fault.