Stan944

The bolts holding the brake calipers are very hard to remove (well above 150 ft lb) on my car. I mean not just loosen them, but turning the wrench over and over.
Is it the design, or the bolts were overtightened, and the threads are damaged?
I alreadu put them back, but for the next time:
I could put new bolts, but the nut is a part of the stearing knuckle, and can't be replaced. Is is OK to uso tap/die to repair the threads? I'm hesitating since I heard these are "locking" (?) bolts.
Other sugestions?
Thanks, Stan

Joe Jackson

Somethings wrong. Sounds like the bolts were either crossthreaded at some point damaging the threads or someone replaced them with a bolt of the wrong pitch (very likely). I can't remember offhand the correct pitch (12mm diameter I believe) but can look it up for you when I get home. Chances are, even though a tap might clean up the threads enough to make a bolt easy to thread in, they probably won't be strong enough any more to hold the torque. If that is the case, you'll need to drill out the holes and install Helicoils or some sort of thread insert. Or, swap out the spindles for good ones. No easy fix here.

peanut

Its probably just surface rust that has clogged the threads on both the nuts and bolts. I never cease to be amazed at the poor quality of fixings used in the 944 I dread trying to remove any of the intake/exhaust nuts and bolts as they have virtually disintergrated through rusting even though I regularly wire brush and oil them.
It shouldn't hurt to run the correct tap through the threads carefully. If the bolts were to shear because they were too tight you are going to be in a bit of trouble.

Greg86andahalf

Could also be Loctite the "red " version of Locktite can make bolts seem welded on. Use PBlaster penetrating oil and let it soak in overnight. When the bolts are out, look for a white powder which may indicate Loctite has been used.

Clean the threads on both the bolts and the Knuckle. then try running the bolts in by hand. A tap and die set makes a good thread cleaner if you use the original size taps and dies. I'd replace the bolts for safety.

greg

Stan944

Thanks,
I use WD40 instead of PBlaster (PBlaster not available around here). Are these two of comparable quality? Honestly, WD40 hardly ever makes a big difference for me...
I'll probably use tap/die next time.

Greg86andahalf

PBlaster is much better for this ap.

billybones

peanut, just a FYI. do not useoil on any threaded parts. that just turns to black carbon.. Use antiseize coumpond. You can get it at most auto parts stores. It is basically flaked aluminum and copper in a moly grease. the grease burns away but the copper and alum... flakes stay to givethe threads something to turn against on removal.. Straight oil just leaves a carbon depsoit,,, well something along those lines but it works.. I ain't no chemist..

Greg86andahalf

PBlaster to get the old bolts out.

I agree with Billy regarding anti-sieze when re-installing the bolts. There's some hi-temp stuff which is good for caliper aps.

Russian Rocket

I know exactly what you're going through, i had to lie under my car and push the wrench with my leg in order to unscrew it. the bolt doesn't even go smoothly, your hand basically starts violently jerking all the way down The worst part is that you had to do it for like 25 Minutes in order to get a bolt out. My guess is that they're rusted inside, when i finally removed mine they were all covered in rust residue 60% along the bolt. PB blaster is not a big helper on this one, i soaked mine for like 1 week and the problem is deeeeply inside the screw hole. It's a big pita to remove them, but when you put them back in throw some antiseize compound on them, it really helps!!!
Vlad.

Stan944

Thanks,
I also put antiseize on the bolts before installation. It definitely helps in the future. With the caliper bolts it didn't help though. I think tap / die is necessary.
I heard that professional mechanics heat them up to red color, and then they turn easily. For now I prefer not to do it, as potential for damage is high.

peanut

When I get a bolt thats so tight it squeaks when it comes out I usually undo a turn at a time then turn it back in. The bolt actually acts like a tap and frees some of the rust and crap from the threads . Its good to spray the bolt to keep it cool too cos if it gets hot it expands making things worse.

Thanks for the tip billy. I would use antiseize on the threads of a bolt going back in but I also wire brush and oil the exposed thread ends of my manifold bolts periodically in an attempt to stop them rusting too much. Oil is good at keeping water and air out to prevent steel rusting.