am i the only one that like torx's...no i really do they are easy to locat a driver onto (particuallrly upside down), have no clearence issues (see that f&^£&^"£^* bolt on the b230 manafold that hex 10mm and right bloody next to an ally wall so u cant get a sodding driver on it....sorry last weekend is still fresh in my brain!

better the torx gives than the bolt sheers in the block (had that happen once on honda motorcycle whilr final tensioning the head (read head & cylinder body) thru bolts - dont even ask !

nope i like them and if you want MY tip on the engine bolts try a warm engien and apply a large lump of cold steel to the head for 30 seconds before you try an crack it!

The torx head was designed in the automotive industry to accomodate robotic assembly, period. Having said that, it's important to have the right tools for the job. When I first purchased my 850 years ago, I realized that if I were to do any work on the car I had to invest in a set of torx tools. So I did. Having said that, I replaced my thermostat years ago. Using the right tool, it was a piece of cake and had it done in less the half an hour.
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'82 240DL Stock / Masters Class, '94 850 Fully Loaded / Daily Driver, CVC / VCOA Member http://www.capcan.com/tonyg.htm

Next time, use a dremel cutting disc and cut a slot in the head. Fit a screwdriver in the slot and put a wrench on the shaft of the screwdriver. Crude, but it works.

I hate those damned things to. Unfortunately, the European makers aren't the only ones getting in on the act. My tried and true all American 1995 Jeep Wrangler was loaded with them, as is my wifes '02 Jeep Grand Cherokee. I've actually broken a few of the tips off my torx bit sockets on the Wrangler, without stripping or screwing up the bolt, go figure. Thank god for Craftsmans no questions exchange policy on broken hand tools, thats saved me hundreds of dollars over the years.

Easy way to test if a bolt is the same thread type, find a nut that fits the torx bolt properly, then find a hex head bolt that fits that nut. Easy to do in most hardware stores that have those walls of bins and drawers full of nuts and bolts. Not so easy in a place like Home Depot where everything is in sealed plastic bags. Either that or just buy a metric thread gauge.

Norm--I had the exact same problem you had when I changed out my thermostat last week. Like you, I cursed Volvo for that damned torx head bolt, and got paranoid about stripping out the insides and took it down to a garage. Part of the problem with the bolt is the sensor right beneath the thermostat housing. The electricity in the sensor has helped galvanize the bolt into the aluminum head. I managed to loosen the front one, but the back one underneath the fuel line was hell to get at because you couldn't use a 3/8's shouldered socket on it. Had to be a quarter-inch. The mechanic came out, took a straight torx wrench and beat the bejeezus out of the top of the bolt, making me white in the face thinking he was going to bust off the ear. But he didn't and the bolt came loose when he threw the muscle to it, so I drove it home and finished changing out the thermostat.

Why did automotive manufacturers change from hex to torx? I think it had to do with the robotisized assembly lines, that a torx bolt was easier to grab and hold on to the end of an automated wrench than a hex. As to what bolt you need--take the bolt and go down to a nut and bolt store and find a metric hex head bolt the same diameter and length. Then take the two bolts and lay them together side by side. If the thread pitch is the same, the threads will mesh and you won't be able to slide the two bolts back and forth against each other. If the pitch is different, the bolts will ride on top of the threads and you will be able to move them back and forth. It's a tried and true method to check before trying to screw them back in the hole and stripping out the softer aluminum threads.

When you're looking for your bolt, buy some thread anti-seize to stop the bolts from galvanizing to the inside of the head again. You'll discover, if you haven't already, that the bolts holding down the cover over the spark plugs are also hard to remove. Crack them loose as a matter of habit and preventive maintenance, including the two on your thermostat and any others you can see going into the aluminum head before they weld themselves in permanently. Dick

Yep, the old stripped torx on the infamous thermostat housing. I don't know for sure but I suspect the reason for there dang things is that the average Harry Homeowner doesn't have a set sooooooo, it's off to the dealer for routine repairs. Most of this stuff is desigined to eliminate the shadetree mechanic and force him to take the car to the dealer for big $$$ on simple repairs. That's why forms like the BB are so valuable. It's saved me thousands over the years. Hex head cap screws are much more convenient IMHO and less likely to strip out the head.. On the torx on the thermostat housing, a universal joint extension or a wobble extension helps a lot. My guess is that a metric cap screw of that size (probably a #10 or 11) would work