I have a 2000 S80 that keeps over-heating. I have had into the volvo dealership twice, and into firestone 3 times now. No one can find out what the problem is - even with 3 different diagnostic tests!

It is not a head gasket , nor is it the radiator, or thermostat. All of those have been checked.
I have also replaced the coolant tank and thought it might have a pin hole in the tank... this did not help.

I have to frequently put coolant in it - which leaks out - then the car over heats.
This has been happening for quite some time.
Has anyone else had this problem?
Thank you.

 

Probably leaking heater hose, heater core or heater core o-rings. See if your driver's carpet is damp.

 

Did you replace the cap ay the same time as the coolant tank?