I have a broken exhaust stud in my engine head. I have an aluminum head but the stud is steel. The stud broke a little below the surface. I want to mig weld a washer to the stud, but will the weld stick to the aluminum or will it blow a big hole in the head? I will only be using a little 110 mig welder.will I be okay or will that lead to more problems?
Drill out the stud, extract the broken stud, refresh the threads and install a new stud. You'll ruin the head if you attempt to weld.
It will blow a big hole in it if you touch it with the arc. Drill a hole in it sized for an easy out. Use that to unscrew it. Go to an auto parts store or good hardware store. They will know what an easy-out is. Make sure you don't drill the hole too big and it must be centered or you will damage the threads. If that happens you can drill it out bigger and get a thread insert, but that will be harder for you to find.
Drill a hole in the center of the stud. Then go buy a bolt extractor bit. With welding you risk damaging the head and or warping the internal threads.
A 110 volt mig might not get hot enough to fuse to the broken stud but you are on the right track. The heat from welding will loosen the stud slightly sometimes enough to back it out with a sharp tool or slot cut in the broken piece. I have removed many broken bolts and studs in aluminum that were deep in the head with tig, by welding a dab of weld at a time and keep building it up till I could grab it with a pair of pliers. It requires precision welding skills but can be done. You might try it with the mig but you must not allow the arc to touch the aluminum. If you weld the washer to it make sure that the washer is not plated it will create more problems for you (health related). Good luck!
