Stripped rear subframe bolt inside trunk

[drew.carlson01]

Hi this is my first time posting and I am currently doing my subframe bushings on my car. The problem I have is I stripped the driver side front stud mount (the one that is inside the unibody) what is the best way to proceed in fixing this? I was thinking helicoil is this going to work? Thanks!

[Mklock]

Cut the trunk and weld in a new bung. You cant really helicoil that specific bolt.

[drew.carlson01]

I don’t have access to a welder and since the subframe is off what is the best way to get it to a welder. Also why do you say I can’t helicoil that bolt?

[pbonsalb]

Did you try rethreading? If not, maybe timesert instead of helicoil. Similar process and I don’t know whether there is a reason you cannot do this.

The car would be a pain to transport with the rear axle removed. Look on Craigslist for a mobile welder who might be interested in the job.

[drew.carlson01]

I don’t think rethreading is possible because it is stripped pretty badly. What is the difference in strength between helicoil and timesert?

[tjm3]

First thing is, that particular fitting is not accessible from the trunk. It's actually under the rear seat just behind the seat belt anchor (pic). Also, if you've already decided to cut and weld, then do it by cutting the curved panel near the seat belt anchor, peel it back, fix the thread and re-weld. I'm not sure you can get a helicoil or timesert to work but you may be able to cut and weld a thick nut or coupler type fix. You're gonna need to get creative just to fix the stripped threads.

The pic is the old and new style panel that has all the forward mounts. Red is the subframe points, green is the seat belt mounts. The one on the left is a broken front/right mount (we're looking at the piece kind of upside down).
The mounts on the new piece are much beefier than the original part.

The other pic is the entire rear subframe with the broken mounts with 'bolts' one dropped into the bushing and the other laying on top, right/front and left/rear, to give an idea of what they look like inside the frame.

I have lots of pics of this operation. Good luck.

[drew.carlson01]

I was hoping I wouldn’t have to cut and weld. Do you think it’s worth it to try to helicoil it and if it doesn’t work then just cut the old one out and weld a new nut in?

[tjm3]

Another $.02. The helicoil and the timesert are both comparable in strength. The helicoil 'floats' (not really but it doesn't bottom out) in the predrilled and tapped hole. The timesert has a lip and the prep tool in the kit cuts the threads and the recess for the lip. It bottoms out, then the insertion too swages the insert and locks it in place. The issue is the threads are up in the mount point so you're not only working at the far end of the hole but I don't remember how much room you have to work. Might work, might not, but like I said, if you're mechanically creative you can probably make it work.

This is what mine looked like before I fixed it and before the fuel tank was removed before the cutting and welding. It's not an M, but a Dinan modded E36 that didn't originally have the reinforcement plates.

[drew.carlson01]

Since the subframe is already out there is plenty of work space so I think I’ll give the helicoil a shot and see if it holds. Since the timesert creates that lip and since it is up in the mount point like you said I’m not sure if there is space for the lip to exist without hitting the inside of the mount hole although I don’t know for sure I’ve never used one.