2008 XC70 intermittent overheating
 

Hello,
Over the last month I have had maybe 4 orange 'high engine temp, reduce speed' warnings, all when I have been in traffic or idle, I just accept them and move on. Today I progressed to a red 'High engine temp, stop when safe'. I stopped, turned the engine off, jumped out and turned it back on and the fans started blowing on high, the coolant was not bubbling. I unfortunately did not check if the fans were blowing before I re-started the car. I left it 10 secs and then went on my way, no other issues today.

The fans seem to work as expected, when the AC is on they are on and as above they came on high to cool today. They rarely stay on after I stop the car. Average temp is mid-90's here in LA area.

I took it to a mechanic today who said possibly thermostat or waterpump, but I think this was mostly guessing. I was supposed to be driving to Utah tomorrow but now probably won't :( in this car as I'm concerned about longer term damage.

Ordered an OBDII reader to get actual temps out of it which will arrive this weekend.

Any ideas? Specifically how would I diagnose if it was the thermostat or the waterpump? Also read could be fan control module (though fans seem to work as expected) or the coolant temp sensor.

Thanks.

NO DON'T -

A common problem with the 6 cyl motors is the thermostat breaks. It's a reasonable replacement for me (45 years in the Volvo repair business) - but others have deemed it not so easy.

Any way, I have replaced many broken thermostats (the entire housing) on the 3.0/3.2 6 cylinder engines.

Yeah I've found alternative arrangements for tomorrow.

How would I narrow it down to the thermostat, if you don't mind me asking?

Thanks

Take it off and look at the broken plastic. Then bolt a new one on. Sometimes a good visual is the easiest thing.

Connect your scan tool and see what the actual temp is in the engine. Use a non contact thermometer to compare the temp in the engine with the radiator.

Yup as you suggested it was the plastic tabs on the thermostat. Quite a poor design.

Thanks for your help.

https://cimg0.ibsrv.net/gimg/volvofo...17f639b91.jpeg