We've all heard the old saying, "Patience is a virtue." Wiser words have never been spoken when it comes to exhaust studs. Unfortunately, if you have to remove a stud, chances are it's because it has already snapped and that renders the patience aspect null and void. There are ways to prevent snapping exhaust studs, but any exhaust repair technician, no matter what calibre, has experienced the broken stud. Now, the repair that was supposed to take an hour or two just doubled.
Before the Stud Snaps
The best friend to any exhaust technician is the oxyacetylene torch. Knowing how to use it is crucial, but sometimes access to the stud presents challenges beyond our control. Since there are several types of exhaust studs; manifold to cylinder head, manifold to front exhaust pipe and, sometimes, even downstream on the exhaust pipes leading to the catalytic converter, you must first determine what you're up against. A stud that runs through two flanges is a best-case scenario. These types of studs can be drilled out and a regular bolt and nut can replace them. But manifold-to-head studs don't offer this luxury. Nor do many front pipe to manifold studs. These studs screw in without access to the other side.
The oxyacetylene torch can be used to provide heat to the flange or surrounding area of the stud before attempting to remove it. The idea is to expand the metal surrounding the stud. If you apply direct heat to the stud and surrounding area, all you're doing is expanding both the stud and the internal threads. The heat will also soften the stud and it will defeat your attempt to prevent it from snapping.
Heat the flange only or the surrounding area near the stud and then employ a stud remover (see Resource 1), or a pair of vice grip pliers to gently turn the stud counterclockwise. A telltale sign the stud is coming out is an obnoxious squeaking. If the squeaking stops, apply more heat before continuing.
After the Stud Snaps
In some cases, no matter how hard you try to prevent it, the stud snaps. The best-case scenario is enough of the stud sticking out to be able to continue to use the stud extractor and torch. The worst case is the stud snapping flush to the flange. Expletives and wrench throwing may help you feel better, but will do very little to help your situation. At this point, drilling out the stud is required. During this operation, you have to be careful not to damage the threads to the mating threads of the stud or you'll have to implement a heli-coil for the stud. But if you drill too much off-centre, you'll compromise the placement and alignment of the intended stud.
High-speed drill bits will need to be used. Left-handed drill bits will work best because they will work to turn the stud in the direction of removal. A small pilot hole needs to be drilled into the stud to start and it needs to be centred or all bets are off. Once the pilot hole is started, jump to the next size drill bit and continue this process until the stud is threads are extracted. Sometimes an extractor can be pounded into the pilot hold and employed to pull the rest of the stud out, but if patience isn't applied, you may find the hole you just drilled is now plugged up with a broken piece of your extractor.
Another way to extract broken studs is to weld a nut to the broken piece and then employ a ratchet and socket to remove the stud. This case can only be used when enough of the stud is accessible to weld the nut onto it.