Subframe weldnut failure?

info2x · Post by **info2x** » 04 Nov 2016, 17:28

It was suggested to me to start this as it's own topic instead of burying it deep inside my leaky Volvo thread.

So here's a problem I never imagined. Today I'm working on the power steering leaks. Since both lines were leaking I figured I would just replace both. I know you can modify the low pressure line, but since the high pressure line was also leaking I settled on just replacing both. After trying to get a wrench on the lines from above and below I came to the realization that the sub-frame needed to be lowered a little to allow access. That's a pain, but OK let's do it.

Jacked the car up moved my stands so I could remove the triangle plates. I removed the 14mm bolts and then went to work on the 18mm ones that hold the sub-frame in. Driver's side was stiff, but it came out. Passenger side started pretty easy and then I found myself with a free spinning bolt. I'm guessing that I'm now super screwed. Any thoughts on what courses of action should be followed? I was thinking of trying to cut the bolt head off, but I'm not sure if that buys me anything.

Does anyone have a picture of this area without the subframe so I can maybe see what I'm working with. If it can be welded from the bottom I can probably get this done in my garage. If I have to cut open the chassis I think I'll have to get t body shop to help me out.

Thoughts?

Post by **theWIFES_S70** » 05 Nov 2016, 00:11

Hey Eric, are you thinking about welding the subframe to the frame somehow? I ask because when I went to replace the motor mounts on my Nissan, I broke a motor mount bolt, one that had a bushing on it. My mechanic removed the bushing and welded it on. And while the ride is not as smooth as it had been with the bushing, and it's now impossible to replace the motor mounts, it's worked for almost a year like that... (The's car's on it's last legs).

Are you thinking about having a shop weld the metal on the frame to the metal on the subframe here? and bypass the bushing? I've seen it work on my Nissan so I could feasibly see it working...

But no doubt it's a hack job... No street cred whatsoever.

But I'd think a weld would be stronger than retapping the threads for the subframe bolts... Especially since those bolts are usually super torqued on.

I can't wait to hear how others chime in. You should post some pictures for us.

info2x · Post by **info2x** » 05 Nov 2016, 10:14

I'll grab a picture this afternoon.

I'm not suggesting welding the subframe to the body though. My suggestion is to perhaps cut into the body so that one can weld whatever I'm threaded into back into place.

Post by **kahl** » 05 Nov 2016, 14:20

You are going to have to cut out a square in the cabin of the floor board. Seat, carpet and pad will have to be removed. Take measurements to find where the center of the bolt is located inside the car. Draw out a 6 inch square on the floor board and use a angle grinder with a cut wheel. Do not make any deep cuts, just the thickness of the floor board. This will expose the unibody rail where the subframe nut is buried. Again marking where the nut is centered cut a two inch square on the top of the unibody rail exposing the nut.
As a precaution note where the fuel lines are positioned under the car. Use of the cut off wheel is on the top away from these lines. Nevertheless you may want to reposition these lines away from any klutzy ops.

I would look in Craig's list to find a fella that can come to your house and re tack the metal pieces you cut out and the retack the nut.

info2x · Post by **info2x** » 06 Nov 2016, 12:47

Can't really see anything in the picture.

kahl wrote:You are going to have to cut out a square in the cabin of the floor board. Seat, carpet and pad will have to be removed. Take measurements to find where the center of the bolt is located inside the car. Draw out a 6 inch square on the floor board and use a angle grinder with a cut wheel. Do not make any deep cuts, just the thickness of the floor board. This will expose the unibody rail where the subframe nut is buried. Again marking where the nut is centered cut a two inch square on the top of the unibody rail exposing the nut.
As a precaution note where the fuel lines are positioned under the car. Use of the cut off wheel is on the top away from these lines. Nevertheless you may want to reposition these lines away from any klutzy ops.

I would look in Craig's list to find a fella that can come to your house and re tack the metal pieces you cut out and the retack the nut.

This seems reasonable although I'm not a huge fan to cutting into the body like this. Anyone had luck with this in the past? Pictures of where you cut and what it all looked like?

info2x · Post by **info2x** » 06 Nov 2016, 16:58

On another note. Once I get the carpet pulled back I have the foam underneath. Looking around it seems that most people suggest just cutting that. Is that still the recommended route or is there a new method?

Post by **cn90** » 06 Nov 2016, 20:11

My thoughts:

1. Leave this alone b/c it is not fun to play with the broken welded nut as you know.

2. If you can lower the subframe just enough (by removing other subframe bolts, but not the troubled bolt) for the Steering Rack job.
Then once done, bolt everything back together.
A broken nut with an intact bolt will hold just fine.
I know this is not kosher but is a shortcut.

info2x · Post by **info2x** » 06 Nov 2016, 20:50

cn90 wrote:My thoughts:

1. Leave this alone b/c it is not fun to play with the broken welded nut as you know.

2. If you can lower the subframe just enough (by removing other subframe bolts, but not the troubled bolt) for the Steering Rack job.
Then once done, bolt everything back together.
A broken nut with an intact bolt will hold just fine.
I know this is not kosher but is a shortcut.

I get where you're coming from, the problem is that the bolt is already lowered a few mm so it's no longer what I would call together anymore and therefore cannot be left as is in my opinion.

GOOD NEWS! I still have my crashed 850 that I use for parts now and then much to my wife's dismay. Well she earned her keep tonight because I used her as a cadaver. As Kahl suggested I took some measurements and figured out approximately where the bolt would be. pulled the carpet back, cut the foam out of my way and found a plug! One of the body plugs matches up with the bolt damn near perfectly. Not sure how it's attached as it doesn't look welded from this side. Plan it to take this apart a little more and see how it's put together.

Post by **theWIFES_S70** » 06 Nov 2016, 21:24

Please keep us posted with this. I can't believe there's a hole for this nut...

I had to do my subframe bushings twice in a few month's time because I had (stupidly) initially installed Proparts bushings, so I know the pain they are to get out and get in. And I was always so "nervous" about all the torque you're supposed to put on those bolts. The only way I could get the appropriate torque was with my 4' cheater and my legs...

I guess breaking it isn't the end of the world, it just makes resurrecting a P80 a hell of a lot harder. Good luck, Eric! We're rooting for you!

Post by **cn90** » 07 Nov 2016, 05:37

There is Red Loctite there, I'd heat it with a propane torch to melt the Loctite.
It will make removal much easier.