~Overheating...

[Clifford Pope]

The thermostat housing is mounted on studs with nuts, fortunately, so the most extreme removal method merely involves sacrificing the nut without damaging the thread on the stud. If gentle tapping with a cold chisel doesn't work I'd use an angle grinder and cut a flat on one side, just clearing the threads. Usually the combination of heat and weakening one face of the nut does the job.

[Clan]

Originally Posted by Clifford Pope

I don't know whether "genuine" Volvo thermostats are better quality, or are they all made by the same manufacturer anyway?

Volvo specification Wahler thermostats are much better quality , they work as you'd expect , for 120000 miles or more , i have noticed QH thermostats react as you say ..

Regarding coolant it should protect down to -37 C when the correct volvo coolant is used in the 50-50 mix get 3 litres of volvo coolant and use to refill , fit and forget , it never needs changing ..

[Patrick Garland]

The basic principle of the thermostat is that water around the engine helps to cool it. As the engine is started it begins to generate heat once it gets to a certain temperature the valve or thermostat opens and allows the water to circulate through the radiator where the air cools the water and allows it to pass back to the engine to cool it. If your thermostat doesn't open at the correct temperature the water around your engine will just keep heating until it boils. If you get a thermostat, put it in a saucepan of water and pop it on the stove you will see the valve open as the water gets hot. Here endeth the sum total of my knowledge on thermostats !!

[morsing]

Originally Posted by Clan

...get 3 litres of volvo coolant and use to refill , fit and forget , it never needs changing ..

?

Until two years have passed, that is...

[Clan]

NO , genuine coolant doesnt need changing it's the best on the market .. ( The coolant they put in at the factory isnt anymore and i would change that after 3 years ) but the coolant you buy from volvo parts is ..

[morsing]

Originally Posted by Clan

NO , genuine coolant doesnt need changing it's the best on the market .. ( The coolant they put in at the factory isnt anymore and i would change that after 3 years ) but the coolant you buy from volvo parts is ..

So all the sludge and rust forming in your engine, you just leave in there?

[Clan]

Rust and sludge in a volvo engine? Only in a realy neglected one . you havent been using the right coolant! honestly .. coolant contains corrosion inhibitor thats just as important as the anti-freeze function , especialy in alloy engines and will keep the engine coolant passages as clean as the day they were made .