So the other day I started to hear a weird grinding noise in my beloved 98 SL2. I noticed the frequency of the noise was about the same as the wheel revolution speed, and it seemed to happen mainly when I had my foot on the gas, it wasn't near as bad when coasting.

I took off the wheel and found a bunch of metal shavings and saw newly worn metal on the CV axle right where it sits over the subframe! The wide part of the shaft looked to be in contact with the subframe. Sure enough turning the shaft a bit I could recognize the same grinding noise. My best guess is the subframe got bent up due to a rock impact or something and now it's grinding on the CV shaft..

I can think of the following options to deal with this

1. Take off the cv shaft and bend/beat the subframe away from the shaft so it doesn't touch anymore
2. Add some shims to where the subframe bolts on to the rest of the car to artificially lower the subframe away from the shaft.
3. Let the shaft keep grinding and hope all the metal gets cleared out so it rotates cleanly, hopefully without damaging the frame/shaft/boot too bad in the process. Seems sketchy!

Anyone got any better ideas?
Not sure if I'm missing anything here, or if there's a better way to fix it.



CV shaft in contact with the frame

 

BTW, it's the one on the front passenger side.

 

I suspect that you have a failed engine mount on that end of the engine.

 

Are you sure the CV axle is still fully engaged in the transmission? Inner and outer joints still properly connected?

I have run over an entire dead deer in my '97 SC2 and I did not bend twist or distort the subframe..
.(It was lying dead in the road on its side so I didn't even pop the radiator)

Make sure you check the engine mounts and transmission mount. If one of them collapsed......

Are yo

 

Thanks for the advice 02 LW300 and derf, you guys are right! I just checked and it seems the studs that anchor the top passenger side motor mount have actually pulled right out of the engine!

It's hard for me to understand why this happened as I don't think they were over-torqued. The only thing I can think of is I drove the car slowly on the steeply banked side of a road for 20 feet last week, which tilted the car quite a bit and would have put some unusual horizontal pull force on the studs. The mount (less than 2 years old!) looked to have failed on one side, so this may have helped create a bad loading on the studs.

I actually ordered a new top right motor mount yesterday in case putting a fresh mount could lift the engine/tranny a bit and get the shaft off the frame temporarily, but I did not imagine that the mount/studs had fully failed!

Has anyone heli-coiled these holes with good results? Or do I need to tap them out to a larger size now?

 

Are you saying the studs didn't back out of their holes, they actually pulled out of the threaded holes in the block, trashing the block threads?

Were these replacement studs or did you use the existing ones with the new mount?

You can't really over tighten them. If you try just like over torquing the nuts, the studs just twist off. I think it's something like 22 ft pounds.

I think it's more likely that the studs began to work their way loose, leaving the stud and melting hole threads and the nuts on the studs to deal with the force of holding up and trying to stabilize the engine on that side. This in turn eventually ripped the mount as well.

Way back in the day, a Saturn Tech told me to always change out the studs when replacing an upper Torque axis mount on the s cars. He said something about wear on the threads and that they were really only designed as single-use items. Maybe this is an extreme example of what can happen. I've never read anywhere about this happening before.

You cannot really go up in size because the through holes in the mount that are attached to the rubber don't have very much diameter difference to play with. You'd have to have somebody machine them out probably to the same ratio as they are now.

Someone else will need to speak to helicoil.

 

I'm guessing that somebody installed the bolts with an impact driver and fractured the threads.

Helicoils if properly installed are actually stronger than the original threads.

If you have not used helicoils before - find someone who has. These are a critical bolt and they need to be done right - which means a straight tapping - and antiseptically clean threads before intallation...

 

I can see the threads on the top parts of the holes are stripped out (and there are aluminum shavings), but there are still some good sections of thread in the holes it looks like. Also there was some weird metallic silver substrate on the threads on the lower part of the studs, it makes me wonder if someone put JB weld or some adhesive down in there previously.

I screwed the studs back in and put on a new mount and the studs are holding the engine up so far, but I'm worried they will come out of the engine again. Should I loctite them in or use adhesive or something to hold better?

Maybe I should keep a heli-coil kit and another engine mount in the car in case it falls out again and I need to fix it

 

The new mount did not come with new studs, so I left the originals when I changed it about two years ago. I know the mount was replaced previous to that, but I'm not sure if they replaced the studs then or not.

 

Does your engine vibrate excessively at idle?

I've never heard of the studs stripping out the holes on the engine. Now I have but you know what I mean.
Sounds like JB weld.
Previous owner truly needed new studs but was too lazy? To get said studs. They kept working loose so they JB welded them in. Unfortunately, If you have a gap between the stud thread and the hole, it will never stay tight. If you JB weld them together, and whichever metal is stronger is going to rip the other threads right off.

Were they possibly cross-threaded and therefore maybe not in all the way? This would explain why only the top of sections of the threads tore out. Because the stud wasn't in contact with the bottom section of threads in each.

I'm taking the time to try to sort this out before you try to fix it because I don't think we are sure yet what the actual issue was. We know what eventually happened, but not how or why it happened. And if we don't address that, it will simply remain an issue. If there's no JB weld at the bottom of those mounting holes, I'm thinking they were crossed threaded and wouldn't go all the way to the bottom.