Stripped Steering Rack Stud Hole - fix?

[Ozz]

Long story short - replaced lower control arms, managed to cross thread the power steering rack studs into aluminum frame when I reinstalled them. Retapped both at stock M12x1.75 size. Fixed one and could get full torque on bolt but the other one stripped the threads before I achieved full torque.

My plan is to drill out the hole in the rack from M12 to 1/2" and use a 1/2 grade 8 bolt after drilling (27/64") and tapping aluminum frame with 1/2" x 13 tap. Since the shank of the stock stud is unthreaded, I'll probably mix a batch of JB Weld and smooth it on where the bolt will be in contact with the rack to simulate the stud.
Not sure if 1/2" is enough larger than the M12 (.46") to achieve good threads. If the 1/2" pulls out, I'm looking at M14 (.5512") - and a trip to the industrial tool supply - as the next step up. Since I have a 1/2 x 13 tap, I'm starting there though.

I've never used helicoils - can I use them here? Are there specific metric vs. SAE sizes? If so, where to get?

Serious PITA! :mad2:

Your thoughts?

[RubberCtyRauder]

Depends on how damaged and "oversize" the hole became when stripped. Suspension stuff, you want to be pretty darn sure it is good to go. I don;t believe heli coils are as strong for suspension..but maybe someone else will know more on them..At work, I use these, in the link below, and they hold up well to repeated fastening and unfastening..not automotive but Injection Molds for damaged, worn mounting holes to mount to the press platen.

http://www.catalogds.com/db/service?domain=ezlok&command=browse&category=root

[drewb457]

just drill out the stripped hole to the specified size and put a helicoil in it

[drewb457]

Depends on how damaged and "oversize" the hole became when stripped. Suspension stuff, you want to be pretty darn sure it is good to go. I don;t believe heli coils are as strong for suspension..but maybe someone else will know more on them..At work, I use these, in the link below, and they hold up well to repeated fastening and unfastening..not automotive but Injection Molds for damaged, worn mounting holes to mount to the press platen.

http://www.catalogds.com/db/service?domain=ezlok&command=browse&category=root

those would work a little better than helicoils

[Krytin]

Helicoils are readily available and will work just fine for this application!

[Spectragod]

If you have a Time Sert kit, that would be an alternate method for the repair.

[Comin' in Hot]

At this point I would also use a helicoil, I know that the actual stud should be able to be threaded in by hand and the actual torque spec is suprisingly low, I just dont know it off the top of my head. It's the torque of the retaining nut that is much higher.

[Ozz]

The problem with readily available/stocked Heli-coils is that they skip from M10 to M14... I'd have to special order an M12x1.75. Belive me, I checked all the auto parts stores and they don't carry them.

Because of this I decided to try to tap it one size larger - which happens to be 1/2". I predrilled the hole to 27/64" (which is proper for aluminum as it leaves 75% of the material in the hole to create the threads) and tapped it with the 1/2" x 13. I had to take the steering linkage off as well as the left tie rod so I could move the rack out of the way to access the hole (left side) with my standard length tap.

I torqued down the new bolt to 76 ft-lbs as specified in the service manual and the hole didn't strip. I'll monitor it for a while but I'd say the repair was a success although I now have one M12 stud w/ nut and one 1/2" bolt holding the rack on.

The new lower control arms that I put on (which is why the steering rack studs had to come off) solved the 'pop' issue I had in the front end too. :)

Thanks for the suggestions. If I find that I need to redo this differently, I'll probably order the correct heli-coil as long as the car is still driveable while waiting for the parts.