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Fiesta 1.25 2010 MK7 With AC - Coolant / Radiator fan issues


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Hi guys, 

Does anyone know what temp the rad fan kicks in at?

So yesterday, my partner was driving home, then hit heavy traffic, at which point steam started venting out of the engine, she didn't remember when the coolant temp light kicked in and there stupidly isn't a gauge in the car.

She pulled over blocking the busiest bridge in Scotland  and called me i got her to whack on the heaters to full, internal fans to full and open the windows before she cooked.

temp light went out and she got home shortly after.

Zero coolant in the expansion tank, i had about 600ml kicking around so i dumped that in to it and it swallowed it up, continued to fill with water and eventually got it full again. oil was a little low and slightly discoloured , more dirty brown then gold and was a little lower than normal, about half way down the stick. IT wasn't white and pasty either on the stick or looking under the rocker cover.

this morning we got it running again and left the expansion cap off for a while, a small amount of really small bubbles was developing on top of the fluid, looked more like what you get when you boil water then anything else.  put the cap on at around 50c and Kept it running i had to go to work at this point so left my partner with it but she didnt have and OBD coms to check temps, she left it running for about another 20 min (30 min in total) and the radiator got hot, shortly after the expansion tank with the fitter cap, was boiling water, which suggests either its getting really hot or theres a lack of pressure in the system.  but the fan never turned on at any point.

So i have a number of concerns, one shes blown a gasket, discoloured oil and possibly the bubbles in the tank making me think that.

Secondly, how did all this happen, is the fan buggered. Can i force the fan on by removing a temp sensor as was the case in previous cars? or what temp should it turn on at

Coolant temp sensor in the thermostat, is that buggered, it seems to be registering on forscan if that is where the PCM gets its temp from ( pretty sure there is an engine temp sensor somewhere, the coolant one deals with the fan?, not sure)

Its been sitting still for the last 2 or 3 hours and the coolant level hasn't dropped and there are no apparent pools under the car.

anyhow, many many questions but I'm hoping someone on here has some experience of these things and perhaps have some avenues to check out, especially around the fan temp.


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the fan would come on well before it boiled. I recall a few years ago a friend had a car. it was overheating. Breakdown service (I can't recall which one) told him the head gasket had gone and towed it home for him. I had a look at it and found the fuse on the radiator fan had blown. We replaced the fuse and it blew again. Then found it was blowing due to damaged fan wiring. That was sorted out and the car was fine for ever more.  

Is fan fuse ok?  I have no idea where the sensor is that turns the fan on.

Some years ago my wife's Fiesta would overheat because the fan came on very late (when temp very high). I rewired the fan so it was controlled manually from a switch on the dashboard. I wouldn't rule out doing such a workaround again if I felt it was easier than solving the original problem.

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I had to have my fan relay replaced as the fan would sometimes not come on causing overheating. Also replaced the plastic reservoir as it had tiny cracks only visible when it was very hot. 

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cheers guys, so i spent the day looking in to this, ECU, Fuse and relay are all good, 14v at the fan connector but she wont play ball, so looks like a faulty fan, cleaned up connectors and nothing. 

Replaced the cap and pressure is maintained, climate heaters are keeping the temps to 80-90c but that's at idle, no climate fans and she boils the coolant,  no mayo as far as i can see sooo, I'm thinking we dodged a bullet here.

Seems ECU kicks in fan at around 90c+ or when AC is turned on at more than 80c.


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