I just replaced the thermostat in our '97, 850. I had such a hard time removing the rear bolt. The torx bolt just stripped out, and I would up removing the fuel injectors to get just enough room to get a tiny vice grip on the bolt. After many, many failed attempts at removal, I was able to get it out. I replaced the thermostat, and replaced the top part. I put the good bolt in the rear, and then ground a slot on the bad bolt to fit a flat screwdriver. I got it all back together and it works like a champ.

What should I do about the bad bolt. I got it in tight, and there are no leaks. Should I just leave it, and deal with it the next time I replace the thermostat? Should I replace it with a hex hed bolt? What thread size is it, and what is it made of (is it aluminum, steel or what)

Any advice is welcome.

thanks,
Stuart