2010 XF Supercharged. The issue first started with
the brake pads low message, then throwing engine over heating warnings. The engine does in fact appear to be overheating. This issue occurs when the vehicle is at idle, sitting at stop lights/drive thrus, or driving at lower speeds. When driving at higher speeds the over heating warning clears. The issue will intermittently clear up on its own, and a local shop analyzed the vehicle and found no over heating conditions. I drove the vehicle for 2 weeks straight, and the issue didn't occur. Now it's back. First the brake pads low message showed up, then engine over heating again.

 

Which engine do you have?

The over heat message might go away when cruising at speed as you are moving a lot of air through the radiators and over the engine (as long as you're not racing the engine) which is keeping it cool enough.

 

Engine is the 5 liter Supercharged V8.

 

I don't know the 5LV8 engine as well, but my guess is that there isn't enough coolant being cooled fast enough. This can be any, or all, of the following:

1. Radiator fan isn't working properly and not forcing enough air over the rad to keep it cool, could be the fan, could be electrical connection to the fan but would expect a DTC if the ECU couldn't talk to the fan - check/replace fan.
2. Thermostat isn't working properly and there's not enough coolant going into the rad fast enough, for the 4.2L these seem to last about 80K miles/8-10 years - change the thermostat.
3. The auxiliary supercharger pump has stopped working, this is a common fault on the 4.2L & 5L after 100K/10 years - check/replace the pump.
4. Electronic temperature sensor is playing up, or the connection to it, I'd would have expected to see a DTC for failed sensor though - check/change sensor
5. There's an air lock somewhere in the coolant system, but I wouldn't expect it to to go away when you're driving - check/bleed coolant system.
6. Water pump is failing, but again I wouldn't expect that to go away when you're driving - check, replace water pump.

Without there being other fault codes I'd start with checking/replacing the thermostat and defo check the SC pump is ok.

 

Thanks for the info. As you stated the number 1 possible reason for this issue could be the Radiator Cooling fan. Other forum members have suggested the same. If the cooling fan is failing though, I don't see how I could have driven the car for 2 weeks straight in stop and go traffic without an incident, but with intermittent electrical failure, anything is possible. I am taking the car to the Euro repair shop for investigation. The shop that checked it last was a general repair shop, not Euro certified.

 

It could be a temperamental fan controller module, you should be able to test this from a cold start. Pop the bonnet and start the engine and turn the AC on high to give it maximum engine load, then monitor the engine temp using the OBDII and watch the fan speed as the engine gets hotter. You can force the engine temperature up by blocking the airflow over the rad with a bit of thick cardboard. The ECU should tell the fan to go faster the hotter it gets. If this isn't happening then the fan/controller is busted. When the coolant temperature gets above 90C the thermostat should be opening and letting coolant flow into the rad, by 100C it should be fully open and the hoses to the rad and the rad itself should be feeling really hot, if they aren't then the thermostat is on the blink.

Don't let the engine overheat, you could cause some major damage to it, I think a usual operating temperature is 84-102C. I don't know at what temperature it starts to complain and raise the overheat warning, but at a guess its somewhere around 110-120C.

 

I definitely can see the fan being the potential issue, to my understanding if the fan control module is bad, the entire fan assembly has to be replaced. Just wanted to confirm if that's the case. Thanks.

 

I've not changed a fan myself so I can't be 100% sure, but it also my understanding that you have to change out the whole assembly as the module is built into it and its not replaceable.