need brake caliper broken bolt help
 

i snapped off the lower left caliper bolt changing the rotors on my 86 420 sel, i drilled out the bolt and then actually broke off the easy out, in the hole, not good- i have the hole cleared now but will need to tap it, -- any hints on how not to continue to mess this up? thanks, i am taking the rotors to a dealer to remove the hub- those hex bolts have disaster writen all over them.

I had the exact same problem on my 380SE. I used up a bunch of bits moving up to the final one, which was just a smit inside the diameter of the threads of original tapped bolt hole. At that point, a tap was sufficient to clear the remnants of the old bolt from the threads. I was very lucky, in that the first hole was centered and subsequent drills went in fairly straight. And, I didn't break off an easy-out either (that sucks)!
The hex bolts on the inside of the hub that hold the rotor are actually quite easy to loosen, but only with a good quality, exactly-the-right-size allen screw bit.

Thanks for the reply- the local dealer wouldnt loosen the bolts for me because i didnt buy the new rotors from him- theres customer service for ya- the local auto shop did it for me for free, maybe took him 3 minutes. anyway after digging out the broken easy out, the hole is just a tad off center , i am thinking of helicoiling a slightly smaller size bolt in, the main stress should be mainly sheer resistance so i think this would work but any feedback is appreciated......thanks

There must be Locktite on the stuck caliper bolt. Did you try soaking it with a penetrating oil? I'd recommend doing whatever it takes to remove the remnants of the original bolt and replace it in kind, even if you end up replacing the caliper.

Loctite usually cannot be broken using penetrating oil. Almost all Loctite products will break down if exposed to 500 degrees F for 5 minutes. Obviously, one has to be careful of surrounding components with this kind of temp.

Try using a propane torch for a couple minutes to loosen the broken bolt, then try another easy out. If you can see the back end of the bolt (take the splash shield off), give it a coule good smacks with a 5 lb hammer and a blunt punch, too.

The propane torch will get it hot enough to melt the locktite without damaging the knuckle -- acetylene torch is way too hot.

Peter

all good advise and much appreciated, i am new to the mercedes world- its a bit more complex than my volvo and way beyond my suburban- Thanks!

pcmaher, thanks for clarifying that penetrating oil has no effect on Locktite. I wasn't sure, but I thought that it might help the stuck caliper bolt situation.