I recently broke off a bolt head in a thermostat housing on my 1984 cj7 and I don't know how to get the broken off bolt out so I can replace it. Does anyone have any suggestions? Would a tap and die get it?

 

You'll need an EZ-Out (tm). There are several styles, but all involve drilling a hole down through the center of the broken off bolt and inserting the tool. The tool will have essentially reverse threads so that when it bottoms out and you continue to turn, it unscrews the broken off piece. Penetrating oil will help. If you are not familiar with the operation you might want to get professional help. The other alternative would be to remove the next higher assembly, i.e. the intake manifold if that is the location of the housing, and taking it to a machine shop. If the housing is in the block you're pretty much stuck working on it in place.

 

The reason the head broke off is due to severe corrosion on the thread portion of the bolt. For this reason an "easy out" will likely not work for this situation. What will have to be done is the bolt has to be drilled perfectly straight to essentially remove all of the bolt. Once this is done, the hole is drilled to a specific size for the installation of a "heli-coil". This is a coiled thread that is used to repair these situations. The decision to make is whether to remove the manifold and let a machine shop do it or try it yourself in the car. You have to be very precise with the drill and a slip will ruin the manifold so it may be worth while to take the time to remove the manifold and take it to a machine shop or take the whole car to an experienced tech to do it in the car.

 

After it is said & done, don't use bolts, use studs as replacements.

 

A dab of "anti seize" would prevent it from ever happening again. The heli-coil would be steel instead of aluminum anyway and wouldn't have the same problem.