Hello,

My 87 240DL wagon has been exhibiting an odd symptom recently and I'm not sure if it's related to the thermostat, an electrical issue, or the cooling system.

Sometimes, and not all the times, when I start the car when cold, the temp gauge will slowly start to climb as usual, and then keep climbing, straight to the top! It doesn't happen all the time, just maybe, I dunno, one out of four cold starts. Tonight it happened when I was just sitting there in the driveway, letting the car get warm-- I like to be nice to old vehicles, let em warm up before driving them.

The thing is, the temp gauge will always, ALWAYS, go back down to the middle after about ten minutes. In fact, the cooling system on this car has always been a champ. Even on long drives in super hot weather, the temp gauge is always slightly below the mid-point, and never above it.

I'm not really familiar with how cooling systems on cars work, but my guess is I either have some kind of electrical problem with my thermostat, or there's something going on with my cooling system where it doesn't start working until the car's been on for a while. I'm really not sure.

One thing I can say is that in the time I've owned this car (three years) I've NEVER drained or flushed the coolant. Ya, bad idea I know. In the past, I've had bad experiences getting coolant flushes at the quick lube places, it damaged an old Acura I had years ago. Is it safe for a 240? Doing it myself looks like a pain, like it requires a lot of basins to catch the flushing liquid without letting it spill into the gutter.

Can someone advise me here?

Thank you for all the help folks on here have provided, I've definitely been posting a lot lately.

 

the thermostat is a purely mechanical device, utilizing a bi-metal disk that pops open/closed based on its temperature. When the engine is cold, its snapped shut, causing the engine coolant to recirculate in the engine block and not go through the radiator. when the coolant rises above a preset temperature (typically around 85C), it opens up, allowing water to go through the radiator. its located under the right angle water fitting that the top radiator hose goes to, on the front left side of the head.

the temperature gauge is reading the resistance of the temperature sending unit screwed into the head just under the intake manifold. this sensor's resistance goes down when the temperature goes up. confusing things, there's a 'temperature compensation circuit' behind the instrument panel that keeps the needle in the dead center of its range unless the engine is too cold or too hot. they put these in to reduce service calls from people freaking out that their temp gauge was moving up and down the range under normal driving conditions.

so... I see two scenarios here.

1) your thermostat is sticking, and not opening until the engine is really hot, then once it opens everything is fine.. sometimes they do this. fix would be a new thermostat.

2) or, your temperature compensation circuit is fubar, and sometimes not working correctly, reading excessively high.

IPD USA actually sells a replacement for the compensator board that removes it and just lets the needle read your actual temperature linearly.

re: warming up... warming up while sitting idling is supposed to be bad for engines. the best thing to do is go ahead and drive the car as soon as its idling smoothly enough not to stall, and just drive gently until the temperature is in its normal operating range.

 

I've heard that too. I recommend it.

Just to add about the temperature compensator board. IPD sells both a new compensator board and a simple jumper wire to get rid of the board and see the "true" temperature. Paying for a 3" chunk of wire with connectors on the ends is too much for me, and the fact that I've had a few bad experiences with IPD is another reason. I would just jumper it with wire and solder.

Here's a link to how to do it:
RWD - How to replace the compensation board with a jumper

 

huh, I've had nothing but good experiences with IPD, excellent customer service, usually very prompt shipment, or good communications when something is backordered. yes, some of their stuff is a bit more expensive than I'd like to see, but they are on my shortlist of vendors for Volvo stuff (along with fcpeuro, tasca, and volvopartswebstore)

 

Is there a way to test a thermostat or would I just replace it? I see aftermarket thermostats are only like $8 from IPD.

Procedure for replacing seems simple, just drain the coolant system, pull the hose of whatever where it's housed, and replace. Any pro-tips?

I need to fix my odometer anyways, so pulling that dash panel apart is going to be a must for me, I suppose I could try jumping that unit as you say. what is the effect on the temp gauge when you say "actual temp?"

Thank you!

 

well, the stock 'temperature compensator' setup essentially holds the needle close to dead center when the temp is anywhere near normal. without it, the needle will wander up and down according to actual conditions, like hot day climbing a steep hill at speed with the AC running, its gonna get pretty warm, cold day coasting down a long grade, its gonna get pretty cold, you'll see the needle reflect this.

re: the thermostat, there's a gasket you should replace. I'm a firm believer in always using real volvo gaskets, and real volvo parts whenever possible. the cheap chinese aftermarket stuff is too flakey.

here's the engine from my 1992 740 turbo wagon, the B230F engines are all basically the same...



see the upper hose on the right (vehicle left side...) ? see that metal elbow fitting where the engine lift bracket is, where that hose is attached to the engine? you take that whole elbow piece off, the thermostat is under there.

the Volvo part, with gasket, is 273459 for 87C or 273307 for 92C, looks like they are $15 at Thermostat kit. Volvo # 273459
(thats a Volvo dealer that sells parts for a reasonable discount). most folks use the 87C one so the engine runs a little cooler.