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Successful broken exhaust stud removal[900/1992] posted by John Sargent on
Sunday, 26 November 2000, at 1:17 p.m.
My wife's 86 745T had several broken exhaust studs. I was able to drill and remove all broken studs but one. In order to remove it, I pulled the head and put it in the kitchen oven, at 225 degrees F., for about 45 minutes. When I pulled the head out, it was at about normal operating temperature. The broken stud came out with torque that would not remove it at room temperature. The thermal coefficient of expansion for aluminum is very close to twice that for steel. Now the kitchen smells like an automotive machine shop. It is a good thing that Thanksgiving was three days ago, or I would be out on the street. My wife would never let me fix my car this way, only hers. If you choose to use this method, I don't recommend locally heating the head, as you might warp it.
Re: Successful broken exhaust stud removal[900/1992] posted by A. Gary DiFrancesco on
Monday, 27 November 2000, at 8:44 a.m.
Last spring I removed the head off my '87 745T due to a broken stud. In my case, the stud broke flush with the head, so there was no way to get a wrench on it. Took the head to a head shop and had the machinist replace all the studs, figuring that if one stud is bad, more were ready to let go.
The machinist trick to removing the remaining studs was amazingly simple and effective. He hooked up the hot side of his welder to the stud, the ground to the block. Set the welder for about 150 amps., then turned the welder on for 2 seconds. The studs after this treatment are hot to the touch, and the head is a bit warm. But the crud in the threads that makes the stud stick is all burned out. It is the crud that is causing the high electrical resistance. Hence, it is the crud that really heats up and burns off. With the curd burned off, he is able to easily unscrew the stud. He finds better than 90% of stuck studs can be removed this way. And there is not warping of the head since the heat is pretty much contained to the cruddy threads and is only applied briefly.
Just one of those welder tricks I have filed away for the day when I get a welder.
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Gary DiFrancesco