Volvo Overheating on Freeway
 

Hello,

I've got an 88 Volvo 240 wagon with about 129k miles on it. I've owned it for about 3 years and it has always been GREAT as far as engine temps. Never went above the 1/2 line. Recently I was having some trouble with the thermostat (I think) during warm-ups. Start the car, and sometimes, maybe one out of every five cold starts, the temp gauge would climb straight to the top, even though the engine wasn't warm yet. Then after about a block or two it would go back down. I was guessing thermostat was sticking, then eventually opening.

I did a coolant flush and that seemed to solve the problem. That hasn't happened since. A week after that I took it to Jiffy Lube (mistake? maybe) and ever since then it's been a bit more finnicky about engine temp.

I drove it from SF to San Diego yesterday and after the first two hours of driving, once I had reached the long, straight I-5, cruising about 80, the temp gauge started going up and I had to let off the gas and slow down to about 60 for it to go back down.

The whole rest of the way down I had to check the gauge and vary my speeds. Sometimes it would stay way low, below the half mark, cruising at 75-80, up hills, whatever, then sometimes, on or off the highway, on surface streets or freeways, barely working the engine or jamming it 65 up a hill, it would creep up. Seemed inexplicable sometimes.

I'm not really sure what could be causing this. I'm pretty sure I did the coolant right; I drained the system, ran a hose through from the reservoir, filled with fresh 50/50 blend, squeezed the top hose to let out any air. Fresh engine oil and good tranny fluid, although my tranny fluid is a little overfilled, but that hasn't caused any problems on long trips in the past. It only started since I visited Jiffy Lube, which was probably a mistake, I only took it there because I had a coupon that made it cheaper than buying the oil/filter. The Lube guys said I had the 'wrong oil filter' on there, which is odd because I took it to an actual auto shop the last time I had an oil change. Who knows.

Anyways, any advice would be great. My first thought is maybe the thermostat is not working right. Other than that, maybe Jiffy Lube guys messed something up, used the wrong weight oil, wrong kind of oil filter, I'm not really sure. Or perhaps a "hot spot" in the cooling system from not doing the coolant right but I doubt that.

Thank you!

Did you ever change the thermostat? It's a $10 part and a bad can cause a lot of damage! It may be sticking OR you may be having a partially blocked radiator; either way your coolant circulation is impeded. Is your heater OK? if so, no air bubble is likely. You can take the thermostat out, I run many cars without one especially in warm climates, to see if things improve... If not, your radiator will be next thing I'd look at.

Thank you for the quick response! Is my heater okay? It works. You're saying if there was air in the coolant system the heater would malfunction?

Sounds like thermostat is in order. Curious, could the flush have loosened but not expelled any gunk in the system, causing a blockage that isn't related to the thermostat?

I wouldn't drive it until you get it sorted out. From what I've read here, one of the few weak points on this block is that overheating will quickly warp a head gasket or worse.

I have some float switches, buzzers and lights ordered to fab up coolant level sensors for my 740's.

Hmm. It never goes to red, it just creeps past half and I slow down. I don't see anything catastrophic unless it is pinned in the red. I have a 40 minute drive tomorrow and I'll see how it goes. Maybe replace the thermostat before driving the 500 mi back to SF.

any other suggestions of what it could be besides the thermostat? I thought air in the system could be expelled by simply idling the car with the radiator reservoir cap off, which I've done.

As long as you stay on top of it, yes.

Hell yes replace that! Probably overdue anyway if it's over 10 years old, the ones I had fail were 10 years or older (although mine failed open, car ran cold).

When you flushed the coolant the first time, did you see a lot of contamination? The old coolant could have been original since you live in a warm region. If so, maybe you did loosen up some crud (I think modern coolants have 'lubes' in them to help water pumps) and lodge something in the thermostat that's preventing it from opening fully, or as Lev said, your radiator is partially blocked due to same. If replacing the thermostat doesn't fix it, you might try recovering the new coolant, doing a caustic flush, replace the coolant, and see if it happens again.

If the caustic flush causes the radiator to fail, then you probably were going to need one soon anyway IMO.

The other thing I can think of is to inspect the temperature sending gauge connections. It could also be the sender, or (less likely IMO) the gauge itself. Hard to imagine that would peg the gauge though (I have an erratic gauge on my '92 that I'm going to sort out once it's back from getting exhaust work).

The only thing I can think of would be to inspect the water pump belt and make sure it's not slack and possibly slipping at speed, then loosen the water pump belt and turn it by hand, looking for any play, etc., although I would be surprised if that's the problem.

Anyway, thermostat first.

Merry Christmas!

I'd verify that engine IS in fact running hot, and you're not just chasing a flakey temp gauge.

I take a lot of risks with engines but one area I am careful with is the cooling system: overheating a Red Block is the major reason by far of engine failure.

Take the thermostat out, run the car without it and you'll know if the radiator is blocked or not... Cheap, fast and easy...

Hello,

Well I didn't replace the thermostat in San Diego. During my 40 miles drive on X-mas day, the car didn't over-heat at all, temp gauge was normal. I went for it and drove back to San Francisco as-is. No problems the entire way. Twice passing through LA the gauge started to creep past the half way mark. I decided instead of immediately taking my foot off the gas, to instead just see what the gauge did. Oddly enough after going to about 3/4 of the way up, it went right back down on it's own to below center. For most of my drive it was below center while I was cruising 70-75 the whole way. Never went past half way between LA and SF. I'm wondering now if it's not the thermostat but some crud that was dislodged when I did the coolant flush. Maybe it occasionally blocks something for a second, I don't know.

Should I do anything about it? I'll probably do the thermostat just for kicks since it's so cheap and easy.

Thanks for all your advice!!

that does sound like an intermittently sticky thermostat.

Once you're driving on the freeway though, wouldn't the thermostat be fully open? I thought it was maybe a stuck thermostat when it would start overheating AFTER I got off the freeway, because the thermostat could have closed, and stuck once I started driving again.