stuck caliper mounting bolt

[72GT]

Ok, the lower mounting bolt for the front brake caliper on my 72GT came off relatively easy. The upper one is not turning at all. I have soaked it in PB Blaster, wrenched and hammered on it for days - seems that it's never going to move!
My next step is to heat it with a propane torch - has anyone done this before? Is there a best spot to focus the heat?
Thanks for your help!
Bob

[greensmurf20]

i have seen my dad heat up the bolts that hold the calipers on, just not on a Opel. so it must be ok to do.

[sleeper]

On my 74 manta it took one hell of an effort with a breaker bar and some liquid wrench to break loose but it worked in the end, the end of the bolt sticks out the other side of the mounting bracket and rusts. I would worry about messing up the caliper with heat, aren't there rubber bits and seals that will cook?

[kwilford]

Have you tried using an impact wrench? A breaker bar will often just snap off the bolt, while an impact wrench works MUCH better in removing seized bolts without damaging them. If you don't have one yourself, electric impacts are available for rent (you need a 1/2 inch drive with at least 250 ft-lbs pf torque, preferably 350 or 400 ft-lbs, and a six point IMPACT socket is mandatory). Or can you get the car down to a shop (even a brake shop) where you might pay a small amount to get the bolts loosened?

I often heat seized bolts with good success, but you will almost certainly have to rebuild the caliper afterwards if you put a lot of heat to it. Perhaps you are rebuilding it anyway? You will also probably damage the flex hose by heating it. If you do decide to try it, put the heat to the steering knuckle that the bolt attaches to, as expanding that more than the bolt will make it easier to remove. An acetylene torch would be better than a propane torch in getting sufficient, concentrated heat to the knuckle, but you probably don't have access to that. If not, use as hot a propane tip flame and as concentrated as you can, to minimize how much heat you apply to the surrounding parts.

HTH

[72GT]

You are right, removing the calipers is my first step in the caliper rebuild. I have new seals, pads/pins and hoses. It appears that someone attempted to actually seperate the caliper halves - the starhead bolts are mangled. I'm thinking, I might just replace the whole calipers rather than rebuild.
I will try an impact wrench before the torch, then maybe invent some fourletter words and finally take it to the brake shop!
- thanks for the advise!
Bob

[opelbits]

If all else fails, try drilling out the bolt before taking it to the brake shop. Start with a 1/8" bit and drill all the way through the bolt. Then step up in 1/16" or 1/8" increments (depending on what kind of bit ste you have or you time). And use lots of cutting oil. If you drill real straight and get close to drilling away the entire bolt, it will collapse with judicious use of a hammer and punch/chisel.

[72GT]

Finally
a 3 foot pipe on the end of the socket wrench loosened the bolt! This was after lots of penetrating oil, lots of noise with the impact wrench (I only have a cheapo 250 ft-lbs wrench) and heating with a propane torch. The bolt looks OK, but I'm going to replace it anyway - along with the two wrenches I damaged in the process.
I'm afraid to do the math - I think I'm averaging about one bolt a week on this car! Two more weeks and I should have the passenger caliper off!

Thanks for everyone's suggestions.
Bob

[doogank]

I had the same issue with my mounting bolts.

LOL, now that you have spent all that time and $$$ to get them off. You then realize you can not get those pins out to remove the damn pads. OMG! Talk about pandoras box!

I would like to hear the follow up on how or if u get those pins out. Because I am at the same spot!!!!

Kel

[merlindavis]

a quick follow up question that somewhat relates to this...

where exactly can a new caliper bolt be purchased? or, what size and thread is the bolt so that a trip to home depot could be utilized?

the lower caliper bolt on the passenger side backed out on a short trip to the DOL on my way to transfer the title of a '71 GT i was purchasing...

[72GT]

I haven't purchased the replacement bolts, yet. But aside from size and thread pitch you should be sure to get the correct hardness. I'm not sure what selection Homedepot has but you don't want to mount your calipers with common steel bolts.

doogank, I was able to get the pins out! I used a hammer and a centerpunch. But I haven't had any luck with the pistons. They're not moving at all. I decided not to put these calipers back on the car, since I have better ones to use.

[namba209]

O. K. Folks, if you do not want to go through all the heat, impact wrenches, 3 foot breakers, etc., before you put the bolts back in, coat the first 1/4 inch of the threads with anti-sieze compound. The same hold true with the pins. Don't be sloppy with the compound, just wipe the pins and coat them. The same goes for manifold bolts, water pump bolts, and anything that could possibly rust or freeze the threads. Two things I always use when assembling anything on my wheels, a torque wrench and anti-sieze compound where indicated. Especially when bolts go into aluminum castings.

Ron

[opelbits]

All your metric bolt needs can be satified at www.mcmaster.com.

Home Depot will not have suitable hardware for your car. They do not carry a decent selection of metric hardware and most of what they do carry is not 'grade'.

[houserc]

I've seen a fair selection of metric at the various "hardware" stores, but DON'T count on the grade. The S.A.E. is NOT high enough at the "hardware" stores.

I found the local VW shops to be a great source for local metric bolts, hex screws, thermostats, etc. I found out that you have to take what remains of the bolt or part you are replacing into most shops.

If you call them on the phone, they won't give you the time of day.

AGAIN, do NOT be fooled into using HomeDepot or, other "hardware" store, generic nuts and bolts for high stress connections. Bad Things!

[namba209]

If you go to your local auto parts store and insist on Grade 8 bolts in metric threads, they usually have a complete assortment hiding behind the counter. I've gotten Grade 8 bolts for all my wheels at AutoZone and Kragens. But to be on the safe side take a bolt or nut with you for thread comparison. The metric bolts come in millimeter lengths and SAE in 1/4 inch lengths. One thing I found is that there is one size in metric and SAE that are close enough that you can screw the opposing nut on the bolt. To safeguard against a mismatch, start the nut on the bolt, run the bolt through the nut and see if the nut will wobble or be loose on the bolt. HTH

Ron

[show no go]

If you want to get rusted bolts or nuts loose without the headache try this: get a candle or any wax and heat the area just enough to melt the wax. if you heat the bolt just enough it will draw the wax in just like sweating copper pipes while plumbing, and 95% of the time the bolt will come right out. Everyone thinks I'm nuts when they see that one whole drawer in my toolbox is filled with old birthday candles. I come from the land of the rust bucket (Minnesota "land of the salty roads") and have used this method many times and it hasn't failed me yet. I learned it from a guy that restored model A's anf T's and wanted to keep every original bolt without ruining them.

[jvandyke]

I'm in the process now too. I tried the PB blaster/propane and wax, extender bar on socket, no go.
Considering either taking to a local shop and paying them to loosen or renting an impact wrench. I hope I'm after the right thing, draggy brake, going to rebuild caliper.

[namba209]

PB Blaster is a penetrant, you gotta let it do its thing, it ain't gonna happen overnight, give it a couple of days to a week for the penetrating fluid to get to all the threads. You gotta remember there has been a fair amount of heat transferred to the bolts and probably a fair amount of water too, so rust is gonna be inevitable. Just remember to use anti-sieze compound on the bolts during re-assembly. HTH.

[West Coast GT]

Another option is to drill it out using a high quality drill bit.

[nobody]

jvandyke, you have replaced the rubber line right? But ya by all means take time and most penatrants do a good job. Sooner or later it will come off.

[jvandyke]

Yes, I've done all three rubber lines. (rear was bad, fronts seemed to be okay (could pass air through easily after removal) but I swapped 'em out anyway) And I've undone this one and moved far away from the action. Alright, I'll let it soak up the blaster for a while, is it possible/advisable to try and soak the other end of the bolt, shooting behind the disk? Between the backing plate and the disk?
PS how hard is it to come by the clips that hold the brake hose/line on? One is missing.

I wondered last night if I'm the first to go after this. Odometer on this car says 52,000. She has a mysterious past though, so who knows. Missing clip suggests someone preceded me, I doubt those come off without help.

These brakes were in a pretty sorry state. Rears don't look to have been operational in a long time. Parking brake lever happily traveled to the top (it seemed) and only engaged the brakes marginally. I replaced the rear hose, both rear cylinders, adjusted as per FSM and set the parking brake so at 3 clicks beginning to engage and takes a very hefty hand to get it to 8 clicks.
I think the last major hurdle is this sticky caliper; it drags more than it should. I put it all back together last night and bleed again. I'm going to sneak the car out and beat on the brakes close to home (empty lot) to find the weakest link, then re-attack that caliper, more PB, more heat, more time. I wonder if my experiment with the wax method interfers with the Blaster's penetration?

[Dmcbrass]

It's a good idea to use anti-sieze compound on bolts; however, remember to lower the torque values accordingly. Anti-sieze is such a good lubricant that you can easily stretch bolts if you use the published torque values.

[GTJIM]

Another thing you can try is to use a bit of 5/8" mild steel rod and place one end on the head of the bolt then hammer the other end to transfer the impact down to the threads - DON'T - hit the bolt head itself with the hammer and keep the metal bar in contact with the head while hitting.

Rapid, tapping is better than big hitting .....

Always replace critical bolts like these after subjecting them to increasing levels brutality - The caliper bolts are M12 X 1.5mm pitch by 37mm long. CAUTION - this pitch is a fine Metric pitch and differs from the standard (coarse) 1.75mm pitch of 'ordinary' M12 Metric bolts.

Use Nickel (silver coloured) Anti-seize on these bolts - not the low temperature Copper Anti-seize.

[jvandyke]

I'll try it.
No luck renting impact wrenches around here, got a guy who I can borow one from but I hate that, feel like a mooch. I'll give him a beer, make myself feel better, better drink it with him, just to be social....if the bolt comes out.

Hard to get a good angle on that thing, maybe I should get a lift, or dig a pit!