Hi All.

I have a weird issue with my 2010 Fiesta Zetec S. So it is losing coolant, I have replaced just about everything to do with the cooling system, thermostat, water pump, new hoses all around, coolant tank, the cap, the drive belts, new coolant with a bleed and the sorts, but I can't get this sorted.

Driving home the other day the car went into limp mode, with the check engine light flashing, no power and was limping. It seemed to be overheating as I could smell a burning smell and coolant tank was boiling over. So I thought maybe head gasket, but no smoke, no coolant and oil mixture, just the occasional loss of coolant.

Waited for it to cool off a bit and proceeded home, it drove fine until I arrived home then the misfiring started.

The next morning I woke up, check under the car for leaks, none at all. Flushed the coolant and bled it again. Drove it, switched on the heater and no heat unless I accelerated hard, at idle the heater would go back to cold. So I took it to a workshop, they checked ignition system and all is well, it's not even throwing a code. Thermostat and water pump are doing their work. They reported to me that the radiator fan is not kicking in (unless they power up the A/C) and it is misfiring and limping especially when it warms up.

What could be causing this?

Had similar issues with the throttle body a few years ago but then it would fail to start so I rule that out.

Coolant temp sensor maybe, since the fan won't kick in when the coolant starts to boil over?

EGR Valve, no smoke what so ever from car.

Head gasket blown, however the symptoms are not there.

I have this same exact issue on my 1.4 fiesta. Did you manage to find the issue?