Hey all,
Now that the cold weather has hit, I've been noticing that my '96 850's oil temperature has been dropping on the highway. Is that normal? I seem to recall the needle would be rock solid at about 3 o'clock, once the engine was warmed up. But now the needle wanders all over the place, from 3 o'clock to as low as 4:30 or even 5 o'clock, depending on city vs highway. I was so worried yesterday, that i pulled off the highway twice and idled the engine to get the oil temp back to 3 o'clock.

Do people have ideas as to what's going on? And, if there is indeed a problem, could it be something I could fix myself?

 

Oil Temp? Do you have an aftermarket gauge? With The factory engine oil cooler setup (on the turbo cars) engine oil is piped thru a cooler in the engine radiator. So the oil temp should be controlled to close to whatever temp the coolant in the engine radiator is. There is also an oil thermostat that keeps the oil in the engine when the oil is cold. (prevents the engine oil from going to the cooler in the radiator until x temp)

 

Oops. I assumed the temperature gauge was oil temperature. Is it coolant temperature, rather?

 

Yes it is coolant temp on the factory gauge - if the coolant temp goes down when driving at speed when cold outside - you might have a broken/stuck open thermostat or someone could have removed it. Easy to replace, two bolts on the thermostat housing (the upper radiator hose attaches to the thermostat housing) there is an oring on the thermostat - no gasket is required and a new oring comes with a new thermostat

If the thermostat is indeed stuck open/missing you might have noticed the heater not working very well also.

 

I didn't even run the heater b/c I wanted the engine to run as hot as possible. Yes, I thought it might be the thermostat, so thanks for confirming my suspicions, and thanks for the tip about how it's easy to replace.

Do you think tapping or banging on the thermostat could get it to become unstuck? Assuming that doesn't work, do I have to drain the coolant before replacing the thermostat?

 

1. No

2. To be less messy you can drain a little - but the radiator drain plug might not cooperate and come out without breaking on a car that old. Less than a quart will leak out if you just undo the thermostat housing - but it might leak onto the alternator.

 

Thanks for your reply. That sounds like it's beyond my capabilities as an amateur mechanic--especially since I don't have a garage to work in. I think I'll get the part but have a professional do it. Would this be the only part I would need to get?: Engine Coolant Thermostat.

 

That's the right thermostat for your engine - but there are many quality aftermarket thermostats (some are the OEM manufacturer) that are the same part sold for much less but not in a Volvo box. As far as "I think I'll get the part but have a professional do it" - I owned a shop for 38 years. I would not install customer supplied parts. Well I would, for up to three times the labor cost and NO guarantee that the part would work or it would actually fix the problem. Nobody ever insisted I put their parts in.

A shop, to stay in business has to make money on both parts and labor to be able to pay for business related stuff - Insurance, workmans comp, salaries, benefits (health ins/vacation/training/etc) utilities, rent, special and scan tools $$$$, and a bunch of other stuff.

You might be able to find someone to install your part - but how are you going to feel when it does not fix your problem? Are you going to write a review exclaiming how that shop ripped you off? (Yes, that's done all the time)

In other words - you are not going to save any money by buying a Volvo branded part and taking it to a shop to be installed. Call your local Volvo specialist, first ask if he will work on a car that old. (many shops won't) If he will tell him your symptoms, explain that you think it might be a thermostat and ask for an approximate cost to replace it. The cost will be diagnosis, labor, tax, shop supplies and parts. He may insist on all new antifreeze - although if in good condition new antifreeze is not needed for just a thermostat, just a top up. (if you clamp the upper hose and the small hose on the coolant bottle you will lose just a few ounces)

 

That makes sense. I'll just bring it in and have them fix it. Fortunately, I have a mechanic I can trust. (Of the 3 I used after I lost my last mechanic, two of them were rip-off outfits--very discouraging... One of them charged triple the retail cost of a part, which I consider excessive--but that was the least of what shenanigans they were up to.)

Thanks for taking the time to help me figure out what's going on and what to do next!

I will post again, once it's fixed, to let y'all know if it was the thermostat or something else.

 

HELP! The mechanic says one of the bolts on the coolant thermostat is seized and he is afraid to apply too much torque because, if the bolt breaks, he would have to install a new intake. He said something about aluminum. I think he meant the bolt was seized because of galvanic action but I’m not sure. (English is not his first language.) He doesn’t want to use an impact driver or apply heat to the bolt.

Does all this makes sense? Maybe the bolt is just rusted out. I would think he could apply heat or use an impact driver. Someone posted a video on YouTube where he successfully used an impact driver to free up a bolt on a Volvo thermostat.

 

I'm sorry but you should find a more experienced mechanic. Yes the thermostat housing is aluminum, and we have been dealing with seized bolts since bolts were invented. Worst case is replacing the thermostat housing which is held onto the head with three bolts that can be removed without moving the intake manifold. If that ends up being needed, note 2 (identical) gaskets are used to seal the thermostat housing to the head.

I do certainly understand any ones reluctance to work on a car that old. Sorry that's just the way it is - many shops put an age limit on cars they will touch. That's why if you have an old car - you had better learn to work on it yourself.

 

Thank you so much for your reply, it's such a great help to have advice from an experienced mechanic!

I live in an apartment building in a tiny studio apartment, do not have a garage to work in, and no room to store equipment. I really love this car, so I'm stuck with trying to find mechanics to do the work. My best mechanic retired after almost 10 years with him. I then tried four different mechanics. Two of them were grifters, as mentioned here above. This guy is honest, and not expensive, so I'm going to try to work with him. I'll go to the other guy, if it doesn't work out.

I will contact the mechanic and tell him what you said. If I understood correctly: if he breaks the bolt, he can replace the thermostat housing -- figure 1 in the diagram -- and needs two gaskets also -- figure 3.

 

If a bolt breaks - 99% of the time you simply extract the broken part. Sure sometimes you might have to drill it out, and rethread or use a helicoil - but that's part of fixing things.

 

Thanks for the explanation. He said something about being afraid to drill it out. I don't know what his reasoning is. I'll ask him what he meant when I pick up the car this afternoon with the bolt still stuck in place. I need it to go to an Xmas Eve family gathering about an hour away by highway. I'm going to take local roads -- about twice as long to get there -- so that sitting at traffic lights will re-warm the coolant. I've found that it's okay in the city, it's the highway where the temperature drops way down and I get scared...

 

The bolt is steel, the housing is aluminum. If you make a mistake centering the drill - you can destroy the housing (aluminum is much softer than steel) But usually the remains of the bolt will come out without having to drill and retap or install a heicoil. If he's not comfortable doing the job - you should find someone with better skills.

 

Roger. I talked with him when I picked the car up. We agreed I'm going to track down the thermostat housing (figure 1 in the diagram -- and two gaskets, figure 3) so that, if he has trouble, he'll have the housing in hand. Thanks again.

 

I blocked the radiator with cardboard so that the engine would run at temperature. In the meantime, I tried various things to unseize the thermostat bolt. I was finally able to do it using a manual impact driver, but now anti-freeze is dripping onto the ground when I run the engine. Is it likely that I cracked the thermostat housing? Or, rather, is it likely that the O rings were deteriorated and wouldn't re-seal the thermostat when I re-tightened the bolts?

 

If you only used the impact driver to remove the bolt, it is unlikely that you cracked the housing (although a "manual" driver could do it). If you did not replace the gasket (I assume 1b in the figure above), then it is not surprising that it leaks. It's standard procedure to use new a new gasket when replacing a thermostat (or just about anything with a gasket).

If you didn't replace the gasket, I would remove the thermostat housing again, clean both mating surfaces (but don't scratch them), make sure you clean the threads of all of the bolts with a wire brush, and reinstall with a new gasket to the recommended torque. I do not know the recommended gasket sealant to use in this application, or if any is recommended, so I would check the service manual.

 

Thanks for your reply. I did use a manual impact driver -- and I whacked that thing probably two dozen times, too. I only loosened the bolt then re-tightened it when I saw coolant dripping under the engine onto the ground. But it still leaks. So, I assume the housing is cracked. But maybe it's the gasket, I dunno. In any event, I'm getting the replacement parts on Saturday and I've got to get it to the mechanic's on Monday. Is there a risk in driving it to the mechanic's? It's not leaking a lot, just dripping. But I read somewhere that it might be dripping onto the alternator, which sounds risky.

 

I think you have a good plan. When you drive in the rain, there is water splashing around the engine compartment, likely on the alternator also. I don't think you will have any problems driving it to the mechanic or even driving it this weekend. If you're really worried, tie a rag around the housing.

My guess is your gasket is leaking, but I suppose you could have cracked the housing. Once you break the seal, it is difficult to reestablish a new seal.

You'll know for sure soon. Sounds like you're a good candidate for a cordless impact wrench (birthday coming up soon?). They're reasonably priced now, but just remember, they are great for loosening but don't use it to tighten anything (well, "perhaps" lug nuts/bolts).