Yesterday the heater in my 94 940 stopped working It blows cold even after driving for an hour. The temp gauge also never gets to the half point. When driving slow, sometimes the temp will slowly go up and I'll get a little heat from the heater. when I get upto speed, the temp will drop all the way back down to the bottom and the heater blows cold again. I have plenty of coolant. Anyone have any ideas before I start replacing everything? Driving when its 10f degrees is not fun.

Another problem that I have been having that might be related. I have a slow coolant leak. From time to time I'll have to top it off. Recently however, the leak has slowed down significantly. Are there common fault points in these cars were coolant leaks from?

Thanks in advance for any advice.

 

First things first, before replacing the heater core.
1) I'm not sure if there is a fuse for the heater since I don't have my owner's manual in front of me. But check that out, if there is one.
2) Flush engine, refill with new antifreeze mixture, and replace the thermostat.
3) Check engine for coolant leaks. They are easy to spot, since they appear whitish when dried on the engine. Look under the waterpump and all the coolant hoses, especially at the connections. You can also go under the car to look while the engine is running, but be sure you don't poke your hands or other body parts near any running parts!
4) If these don't pinpoint the problem, then you may have to give serious consideration to the heater core. I've never done that job, but I heard it was "involved."

Good luck!

 

Ditto; yours are classic symptoms of bad thermostat. Replace it; top up the coolant and then ck for leaks until you figure out where the coolant is going.

A new thermostat should fix your heat problem.

 

Thanks guys! I'll order a thermostat and as soon as its warm enough, I'll replace it and go from there.
Oddly, When I brought the car in for repairs about a year ago, the mechanic replaced the thermostat. It really isn't that old.

 

Yeah, be sure to buy your thermostat from a Volvo dealer. I bought an aftermarket one once and it didn't last one year.

 

That's probably why the one in my car didn't last. He charged me someplace around 10$ for for it. It definitely wasn't OEM.

 

I replaced the thermostat and everything seems to be back to normal. However, in the process of putting the new one in, I snapped off one of the aluminum bolts that hold it in. The good news is it doesn't seem to be leaking at all. It was getting dark just as I finished and I couldn't see if the bolt was replaceable. Is it replaceable?

 

I believe it is. If you can't get it out with pliers, you're going to have to drill a hole into the shank and use a reverse thread extractor. Be sure you do not drill through the sides of the broken bolt and hit the threads in the cylinder head. Otherwise, you'll have more work and headaches.

One of my rookie mistakes was overtightening the exhaust manifold bolt. On the first date with the woman who would become my wife, she asked, "Why do you drive around in winter with the windows wide open?"

After a while, you get a feel for these things. Notice how snug the bolt was when you first loosened it. For small bolts around the cylinder head, I use a 6" long, 1/4" drive socket wrench, and I center the wrench in my hand to snug the bolt down. Then, I might go a bit tighter by sliding my hand down to the end of the wrench.