hey this is my first post to the site and i could really do with some advice. ive owned my 95' 850 wagon for a few months now and i am beginning to have overheating problems, car runs fine for 10 minutes then the gauge begins to rise and when i pull over and check under hood the expansion tank is over flowing with bubbling coolant. i purchased a new tank and a green cap however the problem has not gone away. the coolant is not brown in colour and the oil isn't milky, the fan switches on as it should and ive replaced the thermostat. im a bit lost as to what to try next as i even drained the fluid and replaced it with no success. my mechanic says he does not believe it is the head gasket as the engine runs smoothly. anyone have any ideas as to why my precious car is having problems? thanks

 

It is possible the new thermostat is not working properly.

 

hey there , i have tried running car without thermostat and i have same problem. could this be caused by water pump? as i cant see a leak anywhere and there wasnt the whining you would expect if this was the case. i am very puzzled as to what could be wrong. a new water pump timing belt etc is going to be $1000 to put in which is almost as much as the car cost in the first place.

 

Running with no thermostat will make it run hot. The thermostat is in there to slow the coolant flow down or speed it up to keep it at proper temp. If it is out it is going through the radiator to fast to cool it properly.
But if it has been overheated a few times the head gasket might be gone now.

 

Seems that its commonly accepted that when a head gasket blows that you are going to get oil in the coolant and coolant in the oil....this is not the case. A headgasket can blow through to a water jacket only. Every time a compression stroke occurs it can blow compressed air into the water chamber super heating the coolant and pressurizing the chamber. It does not mean that an oil chamber has been compromised.
A simple test (not 100% accurate) is to stick your nose down into the expansion tank...sniff....do you smell fuel?

 

thanks very much for the advice,

i have come to the conclusion after trying the sniff test you mentioned and draining my radiator coolant again only to see some oil drop into the pan that my head gasket is blown. i have decided that i want to replace the entire motor, as a second hand one would cost as much as having my HG replaced. my 850 is a 2 litre non turbo, would it be possible to replace it with a turbo motor and ecu from the t5? will everything fit in the same? if not what other parts will i need. i cant find many answers about this (at least not a 2.0 litre model) and so far you've both been very helpful

 

There are many write-ups of people attempting this. It is not by any means easy. There is much more to it than just dropping the engine in. There are of course a small handful of success stories but if you ask them, they wouldnt do it again.

Successful 850 N/a To Turbo Swap....yes, It Does Run And Drive, Quite Well I Might Add! - Performance Modifications - Volvospeed Forums

850 N/a To Turbo Motor Swap__ Whodunit ? - Performance Modifications - Volvospeed Forums

Most have started then fizzled out.