S40 V40 Cars: Heater blowing cold with new thermostat

[V40 owner 12]

Hi, for weeks now my 98 v40 has been blowing cold air, so I figured the thermostat was sticking, so I bought one at my local car shop but when I removed the old one, the new one does not have the same flat fitted rubber ring around it, it's a round ring, but once fitted although a bit loose, it went together ok once screwed in. Just as before though it's still blowing cold air, also coolant level appears ok and is on the fill line.
As there is 500+ pages on this site I googled the problem and most of the good results brought me to these forums. So I guess after not finding exactly the answer I'm looking for, my question is, is that non official thermostat any good and should I replace it with a proper Volvo one? And also what else could be causing this?? Any help would be great as my kids, wife and me are freezing!

[stephend]

Personally, I'd start by buying a genuine Volvo thermostat, to be sure it's the correct part. If that doesn't do the trick, I guess you're looking at airlocks, blocked heater matrix, or a problem with the controls...

ps if the thermostat was sticking open, the engine temperature wouldn't get up to normal.

[david philips]

test the old thermostat, it should be closed and if you put it in almost boiling water it should open. if the old one is ok then refit and look for another fault try bleeding the heater or giving it a flush though with a hose in case matrix is blocked.

[m1tch1987]

I would always go with Volvo OEM parts

[pinhead]

a thermostats a thermostat to me, if replaced on any of my cars i just use whats easily available and never had a problem, as mentioned above simply check it by popping in some near boiling water, should see it open

[mikealder]

A simple check you can do with the car is to run it for about five miles to get some heat in to the engine then, with it still running pop the bonnet and feel the temperature of the top hose going to the radiator, if the temp gauge is reading normal then the hose should be hot.
Next get back in the car and set the heater controls to max hot with the blower running, if it's still blowing cold air then you either have an airlock in the system or more probably the heater temp selector has gone kaput - Mike

[V40 owner 12]

Thanks folks, appreciate your replies, I will hopefully report back this week with a result

[V40 owner 12]

Originally Posted by david philips

test the old thermostat, it should be closed and if you put it in almost boiling water it should open. if the old one is ok then refit and look for another fault try bleeding the heater or giving it a flush though with a hose in case matrix is blocked.

How do I do this exactly? Which hose do I take off? And do I remove the cap on the water?

Thanks in advance for any help

[V40 owner 12]

Quick update. Just before I fitted a proper Volvo thermostat and temperature sensor I squeezed all the pipes and I now I have some heat. I have double the heat coming from the right hand vent on the dash only, and the center vents and left vent are cooler? Matrix issue? Anyway fitted the new thermostat and temperature sensor and flushed out the engine and renewed antifreeze. Sadly no change, due to 200k now if it's the matrix I'm leaving it well alone as I've read it's expensive Labour wise. Any thoughts on what you guys think I could try next?

[Dog_Book]

Originally Posted by pinhead

a thermostats a thermostat to me, if replaced on any of my cars i just use whats easily available and never had a problem, as mentioned above simply check it by popping in some near boiling water, should see it open

that's right, aftermarket won't stay as reliable for as long but a new one should work just the same out of the box.