Mercedes-Benz Forum banner

1 - 20 of 22 Posts

Registered
2000 ML320
Joined
247 Posts
Discussion Starter #1
Replaced a cracked torsion bar bearing on the driver side. While I was tightening the bolt to finish up the job the bolt would no longer advance. No mater which direction I went it wont loosen nor tighten....I can't get the bolt out. Have not tried anything drastic yet.
I saw this thread: https://www.benzworld.org/threads/torsion-bar-bolt-stuck.1703262/

This looks like a PIA job to fix. I am not even going to bother trying to fix this my self. I am going to take this to my mechanic. What do you think is the cost to cut the bolt head off or what's the procedure to remedy this? 馃槱
 

Premium Member
02 ML320 06 ML500
Joined
16,870 Posts
The bolt does not go into a threaded hole. On top of the hole is a cage nut. It has rotted away and that's why the bolt is spinning. See nut in PDF.

It's a very tight fit up there but you have to clamp a vise grip around the nut and remove the bolt.
 

Attachments

Registered
Dallas, Texas
Joined
6,844 Posts
Here is thread showing captive nut at the top of clamping lever.


What original MB document does not state is that in order to do one side you have to relive tension on the other side as well.
 

Registered
2000 ML320
Joined
247 Posts
Discussion Starter #4
Here is thread showing captive nut at the top of clamping lever.


What original MB document does not state is that in order to do one side you have to relive tension on the other side as well.
ah crap I only lifted the side I was working on...ugg lesson learned.
 

Registered
2000 ML320
Joined
247 Posts
Discussion Starter #5
The bolt does not go into a threaded hole. On top of the hole is a cage nut. It has rotted away and that's why the bolt is spinning. See nut in PDF.

It's a very tight fit up there but you have to clamp a vise grip around the nut and remove the bolt.
Thank you, I will give it another crack at if I can fit some vice grip into it.
 

Registered
2000 ML320
Joined
247 Posts
Discussion Starter #6
Okay, I spent more than 6 hours trying to loosen the bolt. That cage nut is seized on the bolt. I just can't for the life of me get my vice grip to hold on to the nut. Just keeps slipping. My hands and arms are supper raw. I don't see any other way to to break it loose.
 

Premium Member
02 ML320 06 ML500
Joined
16,870 Posts
Did you use a locking vise grip?

You probably cross threaded the bolt. New bolt required.

A mechanic friend of mine had the same problem and had to make a three way cut on the body floor to access the nut.
 

Premium Member
2002 ML320, 2003 A160, 2002 ML500, 2018 GLS350d
Joined
4,194 Posts
How far along the bolt is the nut? If there鈥檚 not much thread appearing at the top end, you should be able to back it out. Pass a thin strip of metal through the gap at the top of the box, and jam it between the nut and cage. As long as you haven鈥檛 rounded the corners, that might stop the nut spinning. Can you actually turn the bolt, or is it stuck?
 

Registered
2000 ML320
Joined
247 Posts
Discussion Starter #9 (Edited)
How far along the bolt is the nut? If there鈥檚 not much thread appearing at the top end, you should be able to back it out. Pass a thin strip of metal through the gap at the top of the box, and jam it between the nut and cage. As long as you haven鈥檛 rounded the corners, that might stop the nut spinning. Can you actually turn the bolt, or is it stuck?
@43sqd yes I was using a locking one.

I end up cutting a small square hole along cross bar to expose the nut allowing the 19mm spanner in. Managed to make a few turns with the nut not turning but it then became so hard to turn without using a very long breaker bar. It came to a point that the spanner kept slipping off the nut. I tried a torque vice gripe and it too kept slipping off the bolt. The teeth on the vice grip was just gouging the nut and rounding it off. So that nut is stuck on tight. I drenched it with penetrating fluid for a day. Torched it.....nothing worked. So now it seems my only recourse is to cut off the bolt head. The current ride height is at 49mm. So it's sitting pretty low....
 

Premium Member
2002 ML320, 2003 A160, 2002 ML500, 2018 GLS350d
Joined
4,194 Posts
Sounds cross-threaded, so use more blowtorch, vice grip, long breaker bar, and elbow grease/sweat/tears in an anti-clockwise direction only, and back the bolt out of it. Good luck.
 

Registered
2000 ML320
Joined
247 Posts
Discussion Starter #11
Well that was just a horrible experience all around. I spent the last 3 days torching and soaking with fluid penetration to no avail. That god damned nut would not break loose. I end up just saying F--K it and sawsall the bolt off. It was really and I mean really hard (with my poor skills) to cut the bolt off. With the bolt cut off I was able to pry off the cage that was holding the nut. Apparently the cage nut is fastened with two sort-of removable pins. A well placed large flat head screw driver, lots of swearing, and back/fort got the cage off. This was the easy part....I can't believe that a new torsion anchor unit (i believe that's the correct name) complete with bracket, bolt, and cage nut goes for over $350!! I looked every where to find just the bolt and cage nut....nope and nope nothing. I almost gave up was ready to just accept defeat and drop 350 for a new set. But i decided to visit my nearest pick n pull yard. I found a 1999 ML320!!! Poor thing was in such a bad state.....so hard to see something like that lol. Well anyways I got under it and I was able to remove the bolt quite easily and I pried off the existing cage nut the same way I removed my busted one. Paid just 5 dollars for my troubles! I took it home and I cleaned the crap out of them. I made sure to apply anti seize. Everything went in nicely. I set my ride height back to 33mm. Honestly I hope to god I wont ever have to do this again. What an awful design!
IMG_2420 (1).JPG
 

Registered
2003 ml500, 2004 ml350
Joined
586 Posts
Glad you got it done was wondering how it was going along for you. Even thought today in worst case he could cut the head off the bolt.

In the future try a mixture of atf and acetone tests have be done and the outcome is it is better then any penitrating oil on rusted seized parts.
 

Registered
2003 ml500, 2004 ml350
Joined
586 Posts
This is typical thread galling. Dirt, poor lubrication and fast speed are most common causes.
Never heard that term before in relation to bolts. Thats why I love this site if you want to learn it is the place to be. I will read the article.

Probably why we could not get the front shock bolt out of the lower control arm when it snapped off.
Thank you Witek
 

Registered
2000 ML320
Joined
247 Posts
Discussion Starter #15
Glad you got it done was wondering how it was going along for you. Even thought today in worst case he could cut the head off the bolt.

In the future try a mixture of atf and acetone tests have be done and the outcome is it is better then any penitrating oil on rusted seized parts.
The head bolt was recessed in the supporting bracket. My Milwaukee dermal just did not have the power to cut it. It kept auto shutting off. And that bracket is one heck of a thick piece of metal. Nothing short of heavy duty cutting would have been needed. With an angel grinder (using a metal cutting disk) I was able to cut a square through the supporting cross section exposing the nut and bolt. I am not happy I had do that. I am not sure how badly it affects the integrity of the cross member. But none the less I made the square just large enough for a vice grip to fit in and also large enough for a sawsall blade to fit through. After I was done I did spray a layer rust preventing paint. I might go and take my car to a welder and have them weld in a square piece to cover that hole.
 

Premium Member
2002 ML320, 2003 A160, 2002 ML500, 2018 GLS350d
Joined
4,194 Posts
Did you install the grease-filled rubber 鈥渂ellows鈥 over the bolt end? This protects the bolt from corrosion to avoid the seized nut scenario.
 

Premium Member
2002 ML320, 2003 A160, 2002 ML500, 2018 GLS350d
Joined
4,194 Posts
A163 988 01 35 / 1639880135 鈥渃ap鈥

$15 worth of prevention, and the last step in this job that the previous person omitted.
2610969
 
1 - 20 of 22 Posts
Top