Lower rear 10mm brake caliber bolt. Stuck

Supt12 · 02-08-2021, 04:45 PM

I've been reading posts about brake jobs on my 89' C4 and I see that the 10mm hex head bolts that hold the rear caliper on are notoriously challenging to get lose. I actually got lucky and got all but one to break free. Except the lower bolt that must be accessed through the swing arm. I've soaked it in Kriol and added heat to get the juice in deep to no avail and now as you can see the bolt is not looking good.

I've looked at using a bolt extractor but it looks like it might be hard to get a good start on the drill through the swing arm. I'm concerned about hitting the aluminum threads and having to replace the caliper. Has anyone had to deal with this?

I'm looking at removing the swing arm and taking everything to a machine shop for extraction. Who knows what kind of can of worms this might turn into: eek:

Hopefully this is the right place on the forum to ask this question.

AOW162435 · 02-09-2021, 04:04 AM

I would use a sharp cold chisel to nudge it loose. Place the edge of the chisel such that it will turn the bolt counterclockwise when struck. This has worked for me countless times over the years to free stubborn bolts.

Andreas

Supt12 · 02-09-2021, 06:01 AM

Thanks, I'll give that a try. I have a 1/2" chisel in the freezer now.

AOW162435 · 02-09-2021, 06:04 AM

Quote:

Originally Posted by Supt12

Thanks, I'll give that a try. I have a 1/2" chisel in the freezer now.

LOL

Andreas

Supt12 · 02-09-2021, 12:31 PM

A couple hours into banging on the chisel and I have a nice grove on the hex bolt head but no movement. Not the easiest to get a good swing under the car since I only have a quick jack. I'll keep banging but in the mean time, any other suggestions I can try?

Has anyone out there ever had to deal with this particular bolt head striping before braking lose?

Supt12 · 02-09-2021, 02:44 PM

I posted this earlier but I must have done it wrong because it never showed up?

Anyway, a couple hours of banging on the bolt with a chisel and I have a nice notch in the head of the hex bolt but no movement. I did see a wisp of smoke come up and I assumed it was from the braking of tensions but nothing.

This is turning out to be a four month brake job. Has anyone had experience with this particular bolt on the rear left caliber? It's the bottom one that must be accessed through the swing arm. I can't get anything on it. Should I start drilling and try an extractor bit? Or start a complete restoration of the car around getting the one bolt off.

As I posted originally, I've looked at removing the complete swing arm and having a machine shop remove the bolt. Is that what it's going to take?

I could really use a hand here.

Andreas. How important is it that the chisel is cold and why? After it warmed up in my hand I never bothered to cool it off again.

AOW162435 · 02-09-2021, 04:40 PM

Quote:

Originally Posted by Supt12

How important is it that the chisel is cold and why? After it warmed up in my hand I never bothered to cool it off again.

Sorry, I thought you were pulling my leg with the freezer comment! A cold chisel is merely the common name for a chisel used to cut or chip metal (unlike a masonry chisel or wood chisel). It does not refer to the temperature of the tool...

Can you post a better pic of the area around the stubborn bolt? Maybe there is enough room to cut the head off using a reciprocating saw (Sawzall). Once the head is gone, you should be able to remove the caliper. Then it's hopefully a matter of firmly clamping the remainder of the bolt with vise grips and turning it.

Andreas

Supt12 · 02-10-2021, 04:27 AM

Thanks Andreas.

I'd never heard that term and I know that heat/cold can sometimes be used, so I foolishly assumed it mattered. lol, my bad. Anyway, I'll get some better pics and take a look at getting a saw on the bolt. I'll give the chisel some more hits. It's hard to get a good swing because of space.

A friend suggested welding or JB welding a hex key in to the bolt. Welding might be a hard to do without making a mess of the caliper. Anyone had any success with JB weld for this application?

Supt12 · 02-10-2021, 07:32 AM

Supt12 · 02-10-2021, 07:40 AM

Sorry about that third Pic. Didn't spin it first.

The swing and caliper are both threaded so I do not think removing the head would help.

AOW162435 · 02-10-2021, 08:00 AM

I'd be surprised if the caliper mounting ears are threaded. With the head of the bolt removed, the caliper should be able to slide inwards, off the remainder of the bolt, and removed.

My experience is with a few dozen 993s over the years, not 964s, so I could be completely wrong.

Where are you located?

Andreas

Supt12 · 02-10-2021, 09:50 AM

Andreas,

on further inspection of the other already removed rear caliper, you are correct. No threads on the caliper. I thank as long as I don't kink the brass bake line moving off the bolt it should work. I'm sure I could figure out how replace that brass line if needed.

I think I'll JB weld the key in, give that a try and then get the saw out if needed. Once I cut the head off the first option is no longer valid.

Helena, Montana.

AOW162435 · 02-10-2021, 10:05 AM

Quote:

Originally Posted by Supt12

Andreas,

on further inspection of the other already removed rear caliper, you are correct. No threads on the caliper. I thank as long as I don't kink the brass bake line moving off the bolt it should work. I'm sure I could figure out how replace that brass line if needed.

I think I'll JB weld the key in, give that a try and then get the saw out if needed. Once I cut the head off the first option is no longer valid.

Helena, Montana.

Be happy to come by and give you a hand, but you're about 2,128 miles from my house.

Fastening a hex key into the bolt head with JB Weld is certainly an option. Just make sure both the key and the recess are thoroughly clean (brake cleaner). Then let it cure a few days before attempting to turn it.

Andreas

KNS · 02-10-2021, 02:12 PM

You might want to try posting this in the 911 Tech Forum or even Off Topic. Start off the thread by saying there is less traffic in the 964/993 forum (less eyes on it) and you're looking for more help.

The knowledge base in the 911 Tech forum and Off Topic is huge. Both forums , especially Off Topic, have professional mechanics in there everyday. Good luck.

LM964 · 02-11-2021, 02:25 AM

Hi Helena, I couldn't but help notice a few things from your pics that may help - no guarantees though

The chisel you have or used is not a cold chisel - it's a woodworking chisel with a solid plastic handle (by the looks of it). The plastic handle will absorb most of the shock force of the hammer. Also the blade steel is hardened for wood use (not metal) and is easily damaged. A cold chisel is all solid hardened steel for metal to metal force contact. Hope the attached pic helps.

https://5.imimg.com/data5/SI/GT/MY-51134566/cold-chisel-500x500.jpg

The M12 calliper allen bolts (or hex cap/cheese head bolts) are torqued up reasonably high - 63ftlb (or 85Nm) and probably not loosened off ever since leaving the factory. Steel bolt to aluminium interface over the decades certainly doesn't help. Wonder if some other removal tool will help, like stud removal tools (pic below too). Not sure how much room you may have but if a removal tool will fit in the limited space maybe there is a chance.

https://i.ytimg.com/vi/ojn3cYI4wfU/sddefault.jpg

To give yourself as much arm/hand/tool room space as possible I would remove the aluminium brake disk back plate (many owners leave these off). Also, I wouldn't worry too much about the calliper copper/nickel brake pipe being damaged. Least of your priorities for now. Remove it if it helps.

Agree too that posting your challenge up elsewhere will invite more solutions. After all it's a common calliper bolt problem across on any car with disk brakes.

Hope some of this helps. Good luck and be patient, you'll get there eventually

AOW162435 · 02-11-2021, 09:48 AM

Quote:

Originally Posted by LM964

The chisel you have or used is not a cold chisel - it's a woodworking chisel with a solid plastic handle (by the looks of it). The plastic handle will absorb most of the shock force of the hammer.

Good eye! Yes, OP, get your hand on a 6" or 8" long 'cold chisel' with about a 5/8" wide tip. Then attack that bolt head again.

Andreas

Supt12 · 02-11-2021, 04:06 PM

Thanks for the good advice. I decided to try patients and the chisel some more today before posting to the suggested forums.

I have now ruined one cold chisel (old and who knows who ground the hardening off) and now have a new one. I might end up cutting the bolt head in half with the chisel before it brakes.

I give the bolt area 15-20 minutes with the heat gun then hit it with Kriol. Wait for it to cool then bang on the chisel until my arms go to sleep from laying on them and hitting the chisel with a 3lb sledge.

I've bought a reverse drill bit and "spin-it-out" tool. Drill a hole in the bolt and set the spin-it-out and slowly hope it brakes. I kind of have my doubt about getting this bolt free.

I have all those other extraction tools and none will fit in the space.

AOW162435 · 02-11-2021, 04:23 PM

What kind of access is there behind the swing arm? How thick is the swing arm where the hole is (for the hex key)? Can you drill the bolt head through the swing arm? If so, drill the bolt head with a bit slightly smaller than the head. Only drill to the depth of the head. Then hit it with the hammer & chisel. It will come off.

Then slide the caliper free.

Andreas

LM964 · 02-12-2021, 12:28 AM

Wow, really feel for you, this is one bolt that is not going without a fight! Personally I hate dealing with calliper bolts - heat, water, brake dust, galvanic corrosion. A perfect recipe for a seized bolt.

Now probably the time (little choice left) to remove the brake disk with calliper as a unit and deal with drilling the bolt out for stud extraction - or very carefully drill the bolt out gradually up to (and not beyond) its tapping drill size 8.5mm. The brake pipe female nut feeding the calliper might need some persuasion (plusgas etc) before rounding off the hex sides

Disconnect the pad wear indicator and clamp off the brake flexi pipe - may as well bleed all the brakes when refitting the disk and calliper. Good luck.

Supt12 · 02-12-2021, 05:02 AM

Andreas.

Yes there is access for a drill through the swing arm. 2 inches to get threw the hole to the bottom of the head. When you say only drill to the depth of the head, do you mean as deep as the hex would go in. So about a 1/4 inch? I have already started this hole. I need to build some kind of a "sheath" for the aluminum swing arm hole. (don't want to damage) thinking rubber stopper.

LM964.

"time (little choice left) to remove the brake disk with caliper as a unit and deal with drilling the bolt out for stud extraction"

I've looked at this and I believe that I would have to remove the entire swing arm. Is what you are talking about? I'll look at it again this morning but if/when I have to do that I might as well order all the parts to do the bushings and replace bolts. This is a project that I have on the to-do list. The car has 120k miles. I have a parts estimate from Elephant racing to replace the shocks and bushings. lower to ROW and stiffen up slightly for DE and canyon carving.

"very carefully drill the bolt out gradually up to (and not beyond) its tapping drill size 8.5mm."

Can you describe this further? "up to (and not beyond) its tapping drill size 8.5mm"

Thanks again everyone. Maybe today will be the day.