According to the 1991 Owner's Manual for my '91 745 Turbo SE (and the 1990 and 1992 manuals too), the thermostat for the B230FT is supposed to start to open at 92deg. C, or 198deg. F. I have been using the lower temp. 87deg. C, 189deg. F t'stats because that is what the FAQ says.

Now that I can finally get around to replacing the cylinder head on the Turbo, I have ordered the 92. C thermostat for it. Do any of you have any opinion on using the higher temp. t'stat on the turbo engine, or experience with it vs. the lower temp. one? Will it run better (maybe even get a bit better mileage) because it will now run at the temp the computers expect? Will this bring on too high a level of stress on a nearly 20-year-old cooling system? Etc.
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1955 Human, Scott; 1991 745 Turbo, Brunhilde; 1990 745GL, Snuggle Bunny

There is much confusion, never made clear by volvo, for this. None of the green volvo manuals nor the volvo parts specify which to use, just the part numbers for both. The owners manuals do specify but they are inconsistent. If I recall the earlier owners manuals said 92 for the turbo, then they switched at some point and went back again. I believe the turbos were designed to run hotter and should have the 92 thermostat.

I have had both installed and notice no perceptible difference.
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Paul NW Indiana '89 744 Turbo 145K/ '90 745 turbo 127K

Thanks for the correction, which will go to the FAQ.

Steve

I wouldn't worry too much about the difference, and I would expect imperceptibly better mileage.

Regardless of everything else, if your hoses/radiator are original, it's time for a new one. I hated to buy something with plastic end tanks, but my new aluminum radiator cools much better than my 3-row brass radiator, even after it was rodded out.
If you have the brass radiator and replace the coolant, DO NOT use authentic volvo coolant - it will eat the solder. A fact they don't put on the bottle.
Also, people say not to use Dex-Cool, but I'm not sure exactly why.


I'd recommend replacing all your hoses, water pump, radiator, thermostat, and definitely your radiator cap (with the factory pressure). A chain is only so strong as its weakest link, or hose.
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1990 740 Turbo, on its way to stock specs, maybe beyond

Thanks for the info Will. The whole cooling system is new, hoses, pump & everything. The oldest component is the Nissen's radiator which is 6 years old, and will be replaced in 2012 whether it leaks or not. And, since I use the aluminum Nissen's, I use only genuine Volvo coolant. That stuff stays clean and perfect, and keeps the cooling system that way too. It is a bit expensive, though.
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1955 Human, Scott; 1991 745 Turbo, Brunhilde; 1990 745GL, Snuggle Bunny

Sweet! That's good to hear. A lot of people have one new hose and only that one because it had split. Haha, oops.

I'm going to have to set a similar replace-regardless time for my radiator. I hate plastic.

But that's good to know about the Volvo coolant. I would use it, but it's expensive and I'm miffed that the dealer didn't warn me about it destroying my oem radiator. Assuming that was the actual cause.

Happy bricking!
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1990 740 Turbo, on its way to stock specs, maybe beyond