I have a '92 740 Turbo, and I live in Vermont. I had the thermostat replaced last year, when I bought the car from a mechanic and noticed it was cold and not heating up. I noticed today, when the weather turned noticeably colder, that the needle on the temperature gauge only got about 1/4 of the way up (it has been going to about the middle of the gauge). I'm wondering; is the thermostat going bad again? How long should one last? Is it a relatively easy do-it-yourselfer? Thanks!

Once my stat(non volvo stamped but Wahle,supposedly oem lasted one yr only)Change the stat with genuine Volvo ,which comes with a gasket included.If that fails,it's the temp coolant sensor
Tom non turbo 740,90

Normal operating temperature is only about 1/3 up the dial in the dash, not halfway up. Normal operation should involve turning on the car, having it heat up to between 1/3 and 1/2 of the temperature gauge as you initially drive, and having the tstat then open up to cool the engine back down to normal.

I would second the possibility that your bleed valve on the t-stat (the little raindrop metal thing) is installed in the wrong position. You should pull the houjsing and make sure the hole/bleeder is located at exactly 12 o'clock. Note that the t-stat and housing are below the auxiliary coolant tank, so you should you take it off you will get coolant rushing out. You might want to just drain and refill the coolant while you are checking/pulling the t-stat.

As for teh t-stat being shot... that's unlikely after just a year unless you have some other funky coolant problems breaking it.

-Rick

My 1988 240GL n/a did the same thing - on a 200-mile trip, halfway along the temp gauge dropped to about 7:30 instead of the normal 9:00.

First thought was that something blew and the coolant level was down below the level of the temperature sender. Pulled into a farmyard and got a water hose ready. Full boat, no missing coolant.

Drove home, checked the thermostat. Voila! In the rim of the thermostat is a small hole with a little pin in it. They put it there to allow air bubbles to get out, and instruct to mount the T-stat with the pin at 12 o'clock. In my case, and maybe yours, the pin had dropped down and was jammed into the mechanism and kept the thermostat from closing.

I re-installed the T-stat, used Perma-tex on the old gasket, and set the pin at 10 o'clock. Problem repaired, Zero cost, 2 hours work.

Good Luck,

Bob

:>)

Your thermostat may be OK. It is not a hard job to change, but make sure that you get a gasket when you get the thermostat. A couple of things to consider. Is your heater working well? As well as it did last winter? If so, you may be suffering from a loose connection behind the dash cluster.

You can test the thermostat by removing it and suspending it in a pan of water. Heat the water on the stove. If it opens when the water reaches the temperature stamped on the thermostat and closes again when it cools off, it is OK. You will need the gasket anyway if you open it up to look at it.