This last summer I bought my first Volvo. A '91 740. Now that it is getting colder up here is WI I am finding that she doesn't like to heat up or stay heated up too well. If I let her warm up in the driveway the temp. gauge will start going down when I drive her. The only time that it will stay warm is when I am on the freeway for an hour or so. I thought first I would change the thermostat and if that didn't work I would block off some of the radiator with cardboard. Does this sound logical? Anyways last weekend I got a new thermostat and was ready to replace the old one but then I found out one of the nuts holding the thermostat in won't budge and started to round off. Now what am I to do? The wife suggested taking a chisel to the old nut and replacing it with a new one, but I wanted to see if there were any other ideas before I did this. Thanks

What finally worked for me was to chisel straight down on each nut to split it, and widen the split to break the bond with the bolt.

Both nuts were frozen on my '93 940 (car had sat idle for an unknown period) Snake Oils (i.e. P'Blaster and Kroil) applied repeatedly did nothing. Same for torch heat.

IMO, force with a good-gripping 6-point socket is likely to break those fragile bolts.
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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

First try the 6 point socket... 12 points are bad when things are really tight. Go easy, the bolt isn't that big, you can snap it easy.

I would heat it up as mentioned. Just watch the other Rubber components around it. 'Smoke Wrench' is a wonderful tool.
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'75 Jeep CJ5 345Hp ChevyPwrd, two motorcycles, '85 Pickup: The '89 Volvo is the newest vehicle I own. it wasn't Volvos safety , it was Longevity that sold me

If you have an acetylene torch, quickly heat the nut to cherry red. Let it cool slightly, and at will come right off. If you don't have an acetylene torch, it might be worth going to a muffler shop and having them heat the nut.
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john

Try a set of Bolt-Grip sockets -- they're sold at Sears. It's a hardened socket with "teeth" that grip the nut or bolt harder the more pressure you apply. Use PB Blaster first; these things grab the nut so hard you'll be able to break the stud if you're not careful! They're a bit pricey, but really work.
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87 745T, 97 855

What I have found that works sometimes is to take a good hammer and smack the tops of the bolt heads to set up a vibration that might break them loose. If the heads are not completly rounded you might want to try a good Snap-On 6-point socket. Don't know what it is about these but they seem to grip just about anything. A torch wont do any good as the threads are siezed and you wont get enough heat down to loosen them up so the hammer might be the way to go. A good strong WHAP might do the trick if you have the clearance otherwise a good punch on its head would give you a fighting chance.


Cold in Wisconsin eh? Minnesota isnt any better!

988

Get some PB Blaster spray them and let them sit 15-20 min or so then if possible take vice grips and break them free,then get some new bolts to replace the ones you have rounded.
Good Luck
Poolman