Join Date: Mar 2002
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Re: Broken Bolt in Exhaust Manifold
barfnick: I found myself in the exact same situation once upon a busted knuckle... only I was the bonehead that had done the damage in the first place. The heat cylcing those bolts (and the collar) go through is pretty ridiculous, making the bolts themselves very brittle. Having one break is really no suprise, but it still doesn't excuse them "welding" the bolt head on to it to cover it up.
You have a couple choices that I can think of off the bat, depending on how much patience you have...
a) Keep drilling with the same bit (or at least the same size bit) and re-tap the threads. The downside is the bolt material is significantly harder than the cast collar, so your drill bit will have a tendency to try and "slide off" the bolt. Hard to tell from the picture (thanks, by the way - that helps a BUNCH!), but it looks like that may have happened with what you have drilled already. Is what you have drilled so far centered on the bolt hole?
b) You can take a center punch, ding a starting spot in the center of the remaining stud, and start with a very small drill bit. This will go through much easier, then you have a pilot hole. Then use incrementally larger bits to gradually eat out the stud. Eventually, the remaining stud will be thin enough that you can actually just pick it out - probably in pieces.
c) Get some PB Blaster and spray the siezed stud top and bottom. Go have a beer. [img]images/graemlins/40BEER.gif[/img] Make that several. [img]images/graemlins/40BEER.gif[/img] Come back tomorrow morning and spray it again. Place a punch against the remainder of the stud and hit it with a hammer. Spray it once or twice a day and do the mechanical agitation thing (hammer/punch) for at least a couple days. The longer the better. After both you and the sheared stud have soaked for quite some time, drill a pilot hole in the center of the sheared stud. Re-drill it bigger. Get a stud back-out set and see if you can back the stud out. Do not put too much leverage on the back-out wrench (easy to do) or you will shear off the reverse threaded bit in the pilot hole you made (causes a LOT more cussing [img]images/graemlins/cussing.gif[/img] ).
Option "c" will leave you the most material to get a bite on with another stud. Depending on how much material is left from your drilling, you may not even have to drill and tap new threads.
How much material is there left in the collar below what you have drilled? 3/4? 1/2? Keep in mind that with option "b", you will be dependent upon the material that is left in the collar for the new stud threads to get a bit upon. If you have drilled much more than 1/4 of the thickness of the collar, I'd start to have second thoughts about depending on it.
If the hole you have started is not centered, you don't have enough faith in the material left to try option "b", and you don't have the patience/time to do option "c", the keep the drill as straight as you can (harder than it sounds when you're upside down and cussing) and go on through. You'll probably want a carbide bit (at least one). Use low speed and keep the hole oiled if you can. If you're upside down, you'll obviously have to either squirt oil or stop often and dip the bit in oil.
Good luck and keep us posted!