Broken bolts on exhaust pipe/manifold on 1994 GTX

[Rivergator]

Recently my 1994 GTX took on cooling water and it seemed to be coming from under the exhaust manifold. Then I saw a broken allan bolt in the bilge and noticed that 2 bolts on the exhaust pipe/manifold were broken. Actually it was one broken allan bolt and one stud. The remaining 2 allan bolts I removed without a problem, but the one hex bolt that holds the exhaust pipe firmly to the engine (I think it is a M8x35 or 40) broke off as well while trying to undo it. The 2 broken bolts on the manifold I might be able to drill out and extract as is, but that other bolt is in such an awkward position that I either have to remove the 8 bolts from the manifold and remove the manifold or remove the whole engine. What is the best way to go? I don't want to remove the engine if I don't need to, but I am afraid that a few more of the 8 bolts will break when I try to undo them. Drilling out and extracting broken bolts is such a pain. All you guys out there with your bags full of tricks I would love to hear from you. Thanks Rick.

 

[Jeff Walkowiak]

I weld out broken studs those 4 bolts are notorious for falling out or breaking off. weld with a 6011 rod directly on top of the broken stud make sue to take the appropriate precautions to prevent sparks from blowing around inside the hull. After you extend the stud , place a large nut on the new part and weld that real good, while the stud is hot work the piece out by forward and reverse motions do not just turn it out as it will probably bind up and snap off again and you will have to start all over. On the 8mm bolts I just re-tap those holes to 3/8 coarse and buy allen cap bolts to replace the original metric bolts, the 3/8 tap will over size the holes perfectly without the need to drill those original holes out. They are just a bit heavier and hold a lot better. That is how I handle those .

 

[Rivergator]

Jeff, that's an interesting approach. I never thought of or tried welding a piece of material to the stud. Anyway, I tried the 8 bolts holding the manifold hoping for the best and they came out easy and clean. Almost like they were put in there yesterday. Now the manifold is on my bench and I can deal with the broken bolts. 2 have no meat left and probably need to be drilled out, the 3rd one has about 3 mm. I am soaking everything in PB Blaster for a couple of days and then I will try to put the manifold in my vice and see if I can unscrew the bolt. If that does not work I will give your idea a shot. Thanks for all your good advise.

 

[Jeff Walkowiak]

try to avoid drilling out any bolts, that usually ends up going off center , welding them out always works the best for me .

 

[Rivergator]

Jeff, everything is back together. The welding trick did not work for me. The piece of metal I welded to the stud broke off, so I ended up drilling the broken studs out. I agree, staying on center when doing that is a major trick, but since I had the manifold on my bench I mounted it perfectly leveled on my drill press and the drill out stayed right on target. -- Thanks for all your good advise.