Recently my 2010 XF Supercharged developed a intermittent Overheating condition. When sitting Idle at say a drive-thru, the Engine Overheating fault will pop up, once I am driving/moving again the fault clears within seconds, and does not reappear. When the fault is on the dash, hot air is coming from vents even though AC is on. Once fault clears, cold air immediately returns. Any thoughts? Thank you.

 

Pop the hood and run the AC, and see if the fan turns on - I suspect it won't, and that's why your car is overheating, but recovers once you're moving again. Btw - these aluminum blocks really don't take overheating well, so minimize driving and having this happen until you've resolved the fault.

It seems the cooling fans are a common failure point - sadly replacements are not particularly cheap, and I have not yet been able to source a replacement speed control unit, which I think is what fails on these units.

 

Yes, I tried that, the cooling fan or radiator fan is running when AC is on. I checked it on 2 occasions, once at start up, then after driving a bit. What I am going to do is drive the car at a bit longer interval, put it in park, then see if the fan is still running. Will let you know what happens. Thank you.

 

Okay, as expected it's definitely the fan. Fan runs at lower Temps, but once engine is warmed up at idle/stops and parked it is not running. Any possibility a blown fuse or relay could cause? Also where are those particular fuses located? Any help is greatly appreciated. Thank you.

 

I'll share my recent experience with how the fan works.

Mine is a 2015 Sport 3.0SC. I thought I was having fan issues, turned out it was a lazy thermostat. If you have a scanner that can read ECT 1 and ECT 2 it will be easier for you to see what's happening.

I noticed on a hot day that the coolant was reaching 220F but the fan wasn't turning on. When I turned the AC on, the fan would turn on like it is supposed to. This made me pull out my handy scanner and start looking at coolant temperatures. What I noticed is that ECT 1 would be very warm (220F) but ECT 2 would still be showing basically ambient air temperature. The fan is controlled by the temperature at ECT 2, this sensor is located in the thermostat housing. If ECT 2 never warms up, the fan will never turn on.

My local shop replaced the thermostat housing and thermostat which resolved the issue. When watching the scanner you will see ECT 1 warm up like normal, then at around 205F the thermostat will start to open and ECT 2 will start to rise from ambient. Once ECT 2 reaches about 195F, the fan will kick on and bring ECT 2 back down to around 165F (on my car in my cooled garage) then turn back off. This will bring ECT 1 back down to normal operating temperature (around 205F on my car on a hot summer day). This cycle repeats over and over to maintain normal operating temperate at ECT 1.

The workshop manual states that the fan operates at variable speeds to maintain temperature. It doesn't state at what temperature the fan turns on. On my car this is 195F as measured at ECT 2.

I would check to see if your thermostat is operating correctly.

Edit: I see yours is a 2010, my workshop manual says it's for 2011-2015 so some of this may not apply (you may only have 1 ECT sensor).

 

Thanks. With my Overheating condition at stops in traffic, or parked/idle it plays tricks at first. The condition will not occur until the vehicle has been driven a while/fully warmed up. Then the cooling fan stops running properly. It took 30-40 minutes of driving for the condition to occur today.