A couple of weeks ago I mentioned that I had replaced the thermostat on my 240 GLT (because the temperature gauge needle was no longer rising as high as the normal halfway mark) and that, since then, the needle had persistently risen to settle at a point above the halfway mark. It is pointing directly at the little bar alongside the 100 mph mark on the speedo alongside.

The Volvo dealer I bought the thermostat from has since offered me an 80-something degree thermostat instead of the 92 degree one that I replaced. Fitting this would presumably mean that the engine would then run at a lower temperature than the 92 degrees it was designed to run at. But would this be just as harmful as running at a temperature higher than it was designed to run at? What would you do?

Thanks in anticipation, Eric

 

gage has a temperature compensation board that is prone to failure and will give you varying readings(fortunately it can be removed and bypassed, then gage reads actual temperature) . first find out what temp your car is really running at. I would use the standard thermostat if the rest of your cooling system is good, there is no need to buy them at the dealer imho. Running a cold thermostat will use more fuel so I run it the way it was designed. Maybe you just have a bad thermostat.

 

Running a motor cooler isn't nearly harmful as running too hot, but running a motor cooler than engineering specs will cause parts to wear faster. Primarily in your rings, cylinder walls and valve guides. Its not noticable anytime soon, but it will shave miles off of your motors life expectancy.

Cooling systems are one of the most neglected systems in a motor. Sometimes just flushing out the block and radiator with a garden hose can make a world of difference, that and some fresh coolant.

 

Many thanks to Wojeepster and Dingbat for your suggestions. I will start with Dingbat's idea of flushing out the system, then, if that doesn't make an appreciable difference, see if I can find Wojeepster's temperature compensation board. I guess have to find that and bypass it before I can determine what temperature the motor is really running at (or can I do it with some sort of thermometer?).

 

I think all you have to do is start your motor with the radiator cap off, and put a thermometer(like a meat or coffee thermometer) in the coolant and let it get to normal operating temperture, then just comapare the thermometer to the temp gauge. I have'nt dealt with coolant problems in a long time so I might be wrong on that method, but the theory seems right. When you go to flush your system, if you can, pull your radiator out and shake it while you flush it, also pull the temp sending unit and as many connections to the coolant system as you can. This will help all the scale and deposits find a way out and check the holes while your flushing to make sure they don't get plugged up, quick poke with a screw driver is all it takes to clear them. One more thing - mix your new coolant with distilled water(not "spring water"), its not to expensive, available at a grocery store by the gallon and it will make your coolant last longer and work more effeciently. hope it helps

Please keep us posted about the temperture compensation board, I'd like to know were its at and how to bypass it. I don't know if I have one in my car but I like to learn new stuff.

 

http://www.ipdusa.com/ProductsCat.as...668&RootID=629

download the instructions and it will show you where and how to bypass. You can buy their kit or use two computer jumpers with the backs cut off and wire inserted in the back.

 

Many thanks for your further thoughts there, Dingbat. They do raise a few problems, however. Like I don't have a radiator cap I can take off (only the pressure cap on the expansion tank). Nor is my temperature guage calibrated like a thermometer: it just has markings to show where the needle should be (half way up the left-hand side of the dial) and where it shouldn't be (into the red zone). And, furthermore, I rather think that British Volvo 240s don't have a temperature compensation board either!

Meanwhile, I have tried re-fitting the original thermostat that showed me running cold; and the guage has gone back from showing too hot to too cold again. So now I am going to try fitting one more 92 degree thermostat just in case the last one I bought (from Volvo) was faulty. Watch this space!

Eric