Heater box mounting studs broken! What now?

[Ringmaster]

Today's project didn't go very smoothly I tried to replace my rusty old heater control boxes (cable operated units in the engine bay) with nice new ones but the nuts were rusted on that three of the six mounting studs snapped off!

The studs are inserted into the chassis sheetmetal and there is no way to remove them, access them from the back or install new ones....at least as far as I can tell.

Has anyone had this problem? Any solutions? At the moment it looks like I might have to drill new mounting holes in the heater boxes and use self-tapping screws directly into the sheetmetal

[robmog]

you are not alone.
drill the broken studs out, retap and insert new studs.
there is no other way to do it correctly.
your approach would work too, it is the underside of the car.

[Ringmaster]

Originally Posted by robmog

drill the broken studs out, retap and insert new studs.
there is no other way to do it correctly.

Sorry if this is a silly question but how do I install new studs without being able to access behind the sheetmetal

[robmog]

a stud is a bolt without a head.
both ends are threaded so it will screw in from the outside but
still allow a nut to be fastened.

[MikeDL]

According to 101, the studs are welded on at the factory, and cannot be replaced.

Lots of info via search:
Heater Flap/Box mounting studs.
snapped studs; Heater Flapper Box

[Turboo934]

Drill out broken stud, replace with nutsert. Installs some what like a pop rivet.:

[GaryR]

Originally Posted by Ringmaster

Sorry if this is a silly question but how do I install new studs without being able to access behind the sheetmetal

Here is a "how-to" on drilling out a stud, hope it helps..

http://atvconnection.com/Departments/ATV_Tech/Tech-Tip-14-Drilling-out-Exhaust-Studs.cfm

[Tigerrat]

I have not had to do this but the threaded pop rivet sounds like a good idea if there is not enough metal to just thread. I've used these with success in other applications. Ken

[3.2 CAB]

It really depends on how you want the car to be. You could do a very simple, cheap fix, using self tapping, stainless, hex-headed sheet metal screws. It would work fine, but would look a little different, but not that bad. Another choice would be to purchase a new set of the correct sized studs, and grind down what is left of the broken studs, then drill through them, and using the correct size tap, thread the new holes, and screw in the new studs, and finish off with all new hardware. There are several ways to complete the repairs, just have to figure out which is better for you. Good luck!! Tony.

[john walker's workshop]

ain't no drilling out those things. they were spot welded to the sheetmetal, so there is just sheetmetal behind them. i've snapped a sufficient amount of them in my day, in spite of soaking them and going real easy. use one or two sheetmetal screws to the best of your ability. kinda tight up there.

[robmog]

john,
how about drilling them out then welding in a stud?

[drax911sc]

My two cents

[john walker's workshop]

Good luck with that.

[Flackett]

Originally Posted by drax911sc

My two cents

I snapped a stud removing a rusty old heater box from my 3.2 Carrera. I bought cheap M6 x 12mm barrel bolts on Amazon, chopped the head off one and screwed it onto the remnant of the snapped stud and screwed a bolt in from the other side to take washers and a nut. The rubber gasket and replacement box have such generous sized holes I didn’t even need to enlarge it. Contact me if you want to see pictures. Cheers.

[Dpmulvan]

These either welded or 3m panel adhesive work well.