Hi all,

I wonder if anyone can offer any advice before I go back to my garage. I have a 2015 MK5 Mondeo Estate 180BHP Diesel, which has a strange temperature problem.

The temperature gauge goes up past 60, slowly and then will drop back down a bit and this continues until the engine shows as full warm at 90°. It never overheats.

I have recently had the thermostat assembly changed and this has improved the lack of warm air from the vents, but this issue still remains and it is not consistent, so it is not the way the thermostat is operating. (I don't think anyway!) Not unless I am unlucky and have a knackered replacement thermostat.

Is there a separate coolant sensor on these things, if so can anyone tell me where? As searching online for a sensor seems to not come back with much.

Many thanks in advance.

It’s not completely abnormal for the temp gauge to rise so far then come back down a little before rising to the full running temp. This occurs due to the thermostat opening and the sudden rush of cool water into the block.

 

as for poor heat inside that can be caused by many things. A bad thermostat is one potential cause but this is easy to test by checking the upper and lower rad hoses. It could also be the system just needs bleeding. As often there are a few potential culprits you need to go about the diagnostic process in a methodical manner so’s not to waste time or money.