Volvo 2007 XC70 my son bought.
Was overheating, randomly.
Also heater fan in the cab was only on high, then quit working altogether.
I think the heater fan is unrelated as just happen to do at the same time, also when cold weather hit.
I replaced the Heater Fan - the old fan motor did not turn over when wired direct to a battery.
New Fan works perfectly.

Back to the overheating issue - I Replaced the Thermostat.
Still overheating fairly regularly now. As soon as out on highway, it overheats.
If driving slow around town, it seems to be ok. Just running slightly warmer than it should, then it will cool down.
Bleeded system manually, by raising front end, adding coolant slowly, and squeezing top radiator hose repeatedly.

Still overheating, and also noticed (now that Heater fan is blowing) that there is no hot air coming to the cab.
Top radiator hose gets hot, it does seem like the thermostat is working properly.
But other radiator hoses (there are two others) do not seem hot at all.
Engine Fan is blowing on the radiator, all the time, so that is not what is causing overheating.

So, could be one of these options:
- Main radiator is plugged / no flow through it.
- Cab Heater core is plugged / no flow through it.
- A blockage in one of the radiator hoses.
- Or Water Pump - although I would think a water pump would leak or make noise if it was not working.

Is there a way to diagnose? Or do I just have to start taking things apart until I find out what is the cause of overheating.

There is a P0340 Code just started showing up, which is something about the Camshaft Sensor and timing.
Maybe timing belt jumped a cog??
Could this have something to do with it?
It seems to idle smooth enough, but has little power at start up. You give it gas, and it does not do much until slowly gets a bit higher RPM, then it seems to take off and run more normal.

 

1. just purchased the car
2. perhaps now you know why the car was for sale (sorry)
3. Ditto
4. Yes that could be true due to less high pressure air from the turbo being forced into the cylinders (and leaking out into the cooling system)
5. That could be caused by a breach in the head gasket. The combustion gasses being pumped into the cooling system from a damaged head gasket will disrupt the flow of coolant in the engine.
6. Options -- damaged head gasket is not mentioned.
7. use a combustion leak detector on the coolant bottle to test for hydrocarbons in the cooling system would be a good first step.

Does the car happen to have a new/newish radiator? Like it leaked, the car overheated, a new radiator was put in and the damaged was discovered then the car was sold?