Forgot the picture http://986forum.com/forums/uploads02...1576244078.jpg

Whats the thing between the magnet and the bolt?

The Caliper Bolts are 1 time use. As Woody says most likely the Al threads are stripping and galling causing your problem.
I went to Tarret Caliper Studs so I don't have this problem again.

It's just a magnetic wandhttp://986forum.com/forums/uploads02...1576245852.jpg

oh.

yeah, so the aluminum threads of the knuckle are likely stripped binding the steel bolt.

I waited until 6:00 a.m. when it was in the low thirties to heat the knuckle and try again. success! Thanks for all the helphttp://986forum.com/forums/uploads02...1576249443.jpg

Yay! You are lucky.

Yeah, persistence sometimes pays off.
And maybe patience too? Sometimes I think it takes a while for the Liquid Wrench or homemade "Sauce" or whatever to work its way down the threads. Don't have a ton of experience with these, but I'll usually spray some on there, typically followed by a few light taps of a hammer to help loosen things and help the stuff penetrate. Maybe an hour later I'll repeat. Then, if no luck, do it one more time at night and let it sink in over night. Have had some success with it..

there looks to be some schmoo in the threads of that one bolt, so make sure your knuckle threads are still ok.

You going to use some anti-seize upon reassembly ?

I know you really meant that as a statement not a question ;)

Damn I didn't even think of the caliper being aluminum.
Explains the issue.
good to see you got it out

The bolt threads into the upright or knuckle as some people call it. The holes in the caliper are non-threaded through holes

I use a thin coat of anti-seize on my original caliper bolts, they're only 20 years old.

Thanks for the clarification.
Am I correct in assuming the upright is aluminum????
My thought is that at some point in time that bolt was over tightened.
That tends to draw the threads out of the aluminum. Thus the aluminum material in the bolt threads. Also I like to use anti-seaze on anything threaded into aluminum.

Yes the upright and caliper are aluminum but the bolt is steel. I believe it's a corrosion issue as I see it happen on cars that either spent most of their life in snowy conditions or very close to the ocean. The exhaust manifold bolts have a high rate of corrosion issues too..

I got my new bolts today, just waiting on the m12-1.5 tap to clean up the threads.

Tapped, flushed and torqued. Back on the road. After 17 year, there does show signs of the two different alloys fighting each other.
http://986forum.com/forums/uploads02...1576745018.jpg

Hopefully you used anti seize so this won't happen again............

Yes we did. However, 5 minutes down the road one of the ebrake retainer springs went and shut me down. Where do you find those little gems? Are the boxster s ebrake parts the same as 2.5, 2.7?http://986forum.com/forums/uploads02...1576755069.jpg