Temperature Issues

I've got an '82 244 DL that's giving some issues with temp and I can't figure out what's going on. When I bought the car about 8 months ago the temp sensor was dead, replaced that, and the car has always looked like it runs cold. Then about two months ago, sometimes when I was idling at a light the temperature would start to climb higher and higher until I either started moving or turned on the heat and the fan to max, at which point the temp would rapidly drop back down to around the bottom third of the gauge where it usually sat. Recently I changed the water pump and when I saw how dirty the old coolant was went ahead and flushed the system. While the cleaner and water was in it I noticed it was running hot, but not too hot. After draining the cleaner I checked on the thermostat and found that it was an 82* Wahler thermostat that was busted open, which I think maybe explained why the car would take so long to warm up and ran cold? I replaced that thermostat with an exact copy and the car ran very hot, just a little under the redline. I thought maybe it was just a crappy thermostat so bought an 87* OEM one from IPD, put that in yesterday and still the car is running just a tad under the redline. The temperature is very solid there, only drops a bit here and there but doesn't go any higher even after an hour of highway driving, but now turning on the heat makes no difference like it did before. I'm utterly perplexed as to what is causing this. My only guess is that during the cleaning something clogged up the radiator? But I really have no idea.
Thanks.

You may be running into a problem of trying to get a wonky gauge to behave instead of an overtemp situation.

do not rely on dash gauge, get real measurements with an IR thermometer aimed at the thermostat housing.

go from there, as you have described no actual symptoms of a hot engine

If it's not steaming it's not overheating.

That the temp is stable under load says things are good.

I have a hint of concern for you radiator condition, but if it's not overheating ........

I'm with apache, borked guage. Are you aware there is a gauge voltage regulator? Does it work?

I checked the temp of the thermostat housing with an IR Thermometer like suggested and got an average reading of 74 C or 165.2 F. Not sure where this falls in terms of normal operating temperature, any thoughts?

I know the car was in a front end fender bender sometime long before I got it which potentially damaged the radiator, but clearly not enough to cause any serious issues at this point.

My (perhaps incorrect) understanding was that '82 models didn't have the temp compensator that fails on a lot of the later models and can be bypassed, I didn't realize there was a more general gauge voltage regulator, although that makes perfect sense. I take it that it's just a matter of pulling the instrument cluster and taking a look with a voltmeter? If so I'm sure there's another thread on here somewhere I can look up and get an idea of what I need to do.

Thanks for both of your replies.

QisofrKuin said:

I checked the temp of the thermostat housing with an IR Thermometer like suggested and got an average reading of 74 C or 165.2 F. Not sure where this falls in terms of normal operating temperature, any thoughts?

I know the car was in a front end fender bender sometime long before I got it which potentially damaged the radiator, but clearly not enough to cause any serious issues at this point.

My (perhaps incorrect) understanding was that '82 models didn't have the temp compensator that fails on a lot of the later models and can be bypassed, I didn't realize there was a more general gauge voltage regulator, although that makes perfect sense. I take it that it's just a matter of pulling the instrument cluster and taking a look with a voltmeter? If so I'm sure there's another thread on here somewhere I can look up and get an idea of what I need to do.

Thanks for both of your replies.

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take multiple readings at various reading on the dash gauge, figure out what is going on before pulling parts out

A properly functioning 87*C (188*F) thermostat should read just about that with an IR gauge on the thermostat housing. That should put the dash gauge at the upper end of the gauge since that is hotter than OEM.

There is also the temp sensor that could affect the position of the needle.

Hot I can understand questioning the radiator but cool would point to the new thermostat.

TestPoint said:

A properly functioning 87*C (188*F) thermostat should read just about that with an IR gauge on the thermostat housing. That should put the dash gauge at the upper end of the gauge since that is hotter than OEM.

There is also the temp sensor that could affect the position of the needle.

Hot I can understand questioning the radiator but cool would point to the new thermostat.

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I just installed a new OEM 87* Thermostat as that was what was recommended to me by a Volvo tech, and I've taken a couple more readings and that looks like about what the hot coolant is at. I tried comparing the temp between the upper and lower hose to see if the radiator is doing its job and I got a reading around 105 for the lower hose which, to my limited knowledge, sounds like a pretty decent drop in temp. So I'm leaning more towards the faulty gauge, or that the aftermarket temp sensor I put in about 6 months ago was a garbage one.

I've had bad temp senders out of the box. The last one was a coolant temp sensor for the ecu. Had totally incorrect resistance and would have never worked.

dl242gt said:

I've had bad temp senders out of the box.

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Ditto.

Not everything IPD sells is "perfect."

Forgot about it but I had two new-n-box sensors that worked but the hot temp resistance was off by about 20 ohms which was significant on the gauge. Bought another brand to resolve.

Poking around on the www found a Volvo temp/resistance chart.

80* C should read about 184 ohms. I am more familiar with Jaguar systems but that is about right. My experience is that all/most temp sensors are similar in temp/resistance reading.

Short Response: Check the grounds and wiring into your instrument cluster.

Long Version:
Two years ago I picked up a running 1986 240DL for dirt cheap off of Craigslist, as in $200 because the owner thought the engine was shot. The B230 was hemorrhaging oil to the tune of about a quart every mile. Luckily it was less than two miles away from my place so it was able to be driven back and not trailered back. Turned out the intermediate shaft seal had popped out, when the timing cover was removed this seal was just dangling freely. Once all of the front seals and timing belt were replaced out the oil leak was gone.

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As I dug deeper, this car was the poster child of deferred and poorly-performed maintenance as there was also a coolant leak to deal with. The PO had been putting straight water into the cooling system which wrecked havoc on the metal pipes and the water pump impeller looked like a crusty starfish. Got those sorted out and then discovering the leak from the thermostat housing. The thermostat was missing the rubber seal and RTV had been utilized to attempt to seal it up. When originally looking at the car the PO did say he had been putting in water for a while due to that coolant leak and additionally, the cooling system was running at higher temperatures so he put in a lower temperature thermostat. Installed a stock-rated thermostat and finally the wagon was not leaking oil or coolant.










After getting all of that sorted, started to run the engine for more than a couple minutes at a time, that is when I noticed the temp gauge was reading very high. This was happening pretty immediately so the gauge was the suspect and not the cooling system. One of the items I added was a large tachometer and a small clock set up. With the instrument cluster out of the car decided to do the temperature compensation board bypass. At the same time hooked up a voltmeter gauge using the wiring for the clock and ran the + wire into the fuse panel. When reinstalling the set up, the temp gauge needle was sitting almost in the red zone.

High Temperature Gauge Reading


Temp Compensation Board By-Pass (Brown Wire)



After reinstalling the instrument cluster, noticed the gas gauge and voltmeter were both dead. It was at that point I decided to put in a spare instrument cluster and with that one in place, the gauges seemed to work & displayed normally. Took the old cluster and hit all of the male pins and connectors with a wire brush to clean them up. Reinstalled it and the temp gauge was no longer climbing up to the red zone. Additionally, noticed the gas gauge was not reading as high as it had been before. Couple days later took the car out on a 50-60 miles test drive and ran just fine with the temp gauge needle sitting at 9 o’clock the entire time. The ground for the instrument cluster should be black wire in the crescent shaped connector. The other item to check would be if your voltage stabilizer is working and in spec. This is the small three pronged, black rectangle on the very back of the cluster behind the gas and temp gauges.

Original Cluster With Non-op Gas & Voltmeter Gauges


Different Cluster Swapped in


Test Drive With Original Cluster In Place


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polaris said:

Short Response: Check the grounds and wiring into your instrument cluster.




After reinstalling the instrument cluster, noticed the gas gauge and voltmeter were both dead. It was at that point I decided to put in a spare instrument cluster and with that one in place, the gauges seemed to work & displayed normally. Took the old cluster and hit all of the male pins and connectors with a wire brush to clean them up. Reinstalled it and the temp gauge was no longer climbing up to the red zone. Additionally, noticed the gas gauge was not reading as high as it had been before. Couple days later took the car out on a 50-60 miles test drive and ran just fine with the temp gauge needle sitting at 9 o’clock the entire time. The ground for the instrument cluster should be black wire in the crescent shaped connector. The other item to check would be if your voltage stabilizer is working and in spec. This is the small three pronged, black rectangle on the very back of the cluster behind the gas and temp gauges.


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Your experience makes me really think this is an electrical issue. My car has the large clock which never runs, except for the odd times when it does and I come out to the car to find the time has advanced a few hours. My gas gauge also seems to run down at an irregular pace. I just performed a full coolant flush after doing my timing belt and front engine seals since when I drained the coolant it was filthy. I took the water pump and it looked like yours, a complete mess. My thermostat, as I mentioned earlier, also turned out to be broken, thankfully open.

When I bought the car the temp gauge didn't work at all, so when I replaced the wire harness with a Dave Barton one I also installed that temp sensor from IPD I mentioned, and since then have had the oddly low and variable temp signals. Once I finished that coolant flush, water pump change, and thermostat replacement the odd behavior went from low to high, but I'm thinking it may be time to go over the entire gauge cluster carefully and clean things up, check grounds, etc. and just get that job over with. But I feel pretty confident at this point I'm not destroying the poor engine driving it everyday. It's my daily so I was worried at first.

The speedometer needle is also broken off so perhaps I can fix that up at the same time. Anyone know where to pick up a new speedo needle for an '82? Or is it a junkyard only sort of item?

Thanks for such a detailed response.