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Discussion Starter · #1 · (Edited)
I have a 2003 1.8T AWM and I'm trying to install new rear brake calipers w/ mounting bracket. I cannot remove the old brackets because the fasteners won't budge. Mine are not 6-point head but rather take an 8mm allen to remove. I tried a impact driver at the highest setting and nothing. I tried my breaker bar and broke my 8mm socket attachment. It's a GreatNeck 8mm allen/hex and doesn't look like it's meant for that type of torque since it's a 2-piece with the bit looks like compressed in.

I have not used a propane torch because I'm worried about how close it would be at the top fastener to the brake lines. I suppose I could take the caliper off the mount and then move those lines out of the way (If I'm remembering what it looks like right). Also I will have to get an 8mm hex bit socket so I will probably go for a 1-piece impact bit this time. Home Depot doesn't carry the 8mm hex bit impact in-store but Harbor Freight might, I have to call when they open. Still I am concerned because if I use my impact wrench I might strip the fastener head. I just don't think it can take that impact wrench type of torque. The impact driver has already caused the 8mm hole in the head to widen slightly and I can see the markings in it. In other words an 8mm allen is slightly loose in the head of at least one now and I expect with more torque it gets worse.

Any suggestions? Also I want to order replacement bolts but I sure don't want to go through this again. I found N 906 889 01 in ETKA (part# is for front wheel drive vehicles only, also N90688902 supercedes N90688901 ) which is M10X1.25X20 with the female 8mm hex head. I'd like to replace it with a six-point head (a male hex head) to make it less likely to strip at the head but who knows what alloy they're using or how those screws are made. Do you think it's safe to replace with some other part that is also M10X1.25X20? These seem like pretty important bolts since no rear brakes if they come off. The manual I have for Audi B5 says the torque is only 44 ft-lbs for the socket bolt (I think what this is), and 70 ft-lbs for something called a ribbed bolt.
 

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Discussion Starter · #3 ·
Thanks for the suggestion, I actually broke the left rear free last night but did not have time to update the thread. I needed both propane and my impact wrench at its highest setting. Here's exactly what I did, for the benefit of anyone in a similar situation:

I bought a metric allen impact driver set (crmo) from Harbor Freight. They were the only hardware store around me I could find that stocks an 8mm allen attachment for a 1/2" impact wrench. I attached it to my Ridgid Impact Wrench (R86011) which has 450 lbs of breakaway torque (supposedly). I put it on the highest setting, 3, and those bolts still would not budge even after 15 seconds of impacting. Wow. At least I didn't break the heads off. And yes, I had it in reverse :) I even tried eliminating a 1/2" extension on one of the bolts (in other words tool directly to attachment because you lose torque with every extension piece on an impact) and still nothing.

So next I tried propane. First though I removed the emergency brake cable out of the way and undid the brake line and clipped it to the strut to get it out of the way. The brake line was a constant drip-drip leak so I had to catch the fluid as well. For each bolt I set a 2500F heatshield felt that I put right above the head area I was working to limit the heat. Even though the brake line is technically out of the way the heat rises and would have caught the line so I just configured the felt like a little hood to direct it away. I used a TS8000 torch which is a ridiculous torch at its highest setting so I had it turned down somewhat. I heated each head for about 20? seconds (they weren't glowing but looked like the color was going to change). After that I got them off within 5 seconds each, even with a 1/2" extension back on the impact wrench. I used impact immediately after heating so it was heat->impact, heat->impact and not heat->heat->impact->impact.They were smoking hot when they came off. I did not see any loctite on them. I did not reuse them.
 

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If you can get a good swing with a hammer try rapping the head of the bolt a few times pretty hard straight on. Put your Allen into it and drive the bit with a few good blows. Use a good size hammer like 2-3 pounds. The shock often loosens things up.
 
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