The engine temparture is acting weird in my car. Prior to last week, engine temp would rise nicely to the halfway mark on the aguge and stay there. Then suddenly it started misbehaving. Now at highway speed, the engine temperature drops almost all the way back down and when I stop the car, the electro-static radiator fan keeps going for quite a while even though the outside temp is -15 Celsius

Stephane

You need to replace your thermostat and thermostat sensor. It's an easy job...

Yes, Again -"replace your thermostat and thermostat sensor..."
There's also other similar posts. I beliefve if you don't soon cold running could cause other problems to pop up. we had soonner than later an Air-pump failure then a front O2 sensor go bad... figure that?
D~

That sounds like what happened when my thermostat failed. Has your "check engine" light come on yet?

-Sam

No engine check light yet. I'll book an appointment to get the thermostat fixed.

Thanks

I had the same problem recently. Changed the thermostat and ECT sensor. You can get the parts for $12 and roughly $60 online, or add 20-30% from the dealer.
If you don't need to replace the coolant just clamp off the upper hose, screw off the housing and careful not to drop the screws down there. (If not doing yourself, caution your mechanic). Lift it straight up with screws in then remove. Ect sensor unscrews and plugs right in. Took me 10-15 min. Also make sure the thermo goes in bleeder valve facing fwd!!
I followed the descriptin on volvospeed.

Cheers

I also just encountered this problem during record cold in New England. Any idea what causes the thermostat and ECT to fail at the same time?

Bay 13 suggests using a 7 inch long 40 torx bit(3/8 drive) to remove the thermostat cover, but my auto supply/hardware stores only carry a torx 3/8 inch socket that is too short and fat to reach the back screw. Can anyone suggest a source for the longer torx bit?

If I don't want to drain the coolant, what kind of clamp are people using on the radiator hose to prevent spillage?

Thanks.

its not that they necessarily fail at the same time, but its well worthwhile to change both while you are there. They both have the habit of failing and no point doing the work for one only to find out the other was the problem.

It's been so cold, I had to try changing the thermostat immediately. I have an ECT on order, but so far the problem seems to have been fixed. Thanks.