Help.. ran into problem during lower ball joint removal!
 

Hi guys.. I got a problem on my hands. Everything is going well... EXCEPT the darned nut thats attached to the upper ball joint. This is a 126 300SEL. The nut just keeps spinning. Its moving... because I see it move, and the nut is not stripped, however I spent a good 10 minutes turning the nut but its not coming off. I don't think it even moved much. What should I do???:( I need this fixed ASAP since this is my only car. Help on this matter is greatly appreciated....

P.S. This is my first ever "project". I wonder if replacing the lower ball joint is too advanced for a beginner DIY, but I am up for the task:D

Sounds like you need a nut splitter

Hmm... the nut is not stripped, just it keeps turning around the threads, but not coming off. Don't know how thats possible. Before I get nickel and dimed to death with buying more parts.. is there another way to work around this????

The ball pin (that is the shaft that your nut is on is called in MB speak ;)) is rotatating. Jam a self made tool in there to wedge the pin back into the "cone" by levering the nut away from the knuckle and then unscrew nut while levering it. I've used a small crowbar and it worked. Job #33-400 (check step 13 on assy. to see what I'm talking about). I think this will help.

On some aftermarket UCA's there is an Allen receptacle on the end of the threaded shaft (pin), but not on OE or OEM, as far as I've seen.

Put a floor jack under the control arm and lift up on the arm hard (so the vehicle is almost raising up on that corner) and then loosen it. The added pressure should keep the stub from rotating. In a shop, you can usually get these to free up by repeatedly reversing with an impact gun.
The hard part about this job is getting the ball joint out of the steering knuckle and reinstalling it.

Gilly

jbaj007... thanks for your input. I took a look at the diagram on how to make the tool, but am a bit confused. It doesn't tell me the units. cm would be too big, and mm I think would be too small. Let me know if this is the tool you're reffering to.

You can also use slip joint pliars to hold the tapered pin in the lower control arm joint and unscrew the nut. You're actually lucky because I had to buy a longer two jaw puller to pop the joint. My shorter one became slightly twisted.

My bad. I didn't understand the problem initially.

I just referenced the tool (which is more for installing than removing) and the area of the FSM so you would see the idea of the shaft rotating.

The diagram is in millimeters. I wouldn't bother making the tool, though.

Gilly's method or wbain's are more in line with what the pros would do; so I'd just do that. A short demo bar worked for me.

update: I went and followed the advice some of you gave and still no luck. I used a different tool this time so I can see if the pin is actually spinning with the nut or not. I can positively say that the pin is not moving but the hex is. I don't know how its possible... but it is. I can't tighten nor unscrew the hex, it just spins in place. I tried various techniques... nothing works :( I hate giving up half-way into the job

Hmmm...maybe my advice is good after all. :)

It might be the tool I need to get a hex nut off, but it will have to wait. I am not going to shell out $70+ for something I will use once. I will wait untill the UCA will need to be replaced and then use a dremel tool to cut through that SOB. Thanks for the help though... i'm just frusturated when I have to stop half way. Oh well.

I think you're describing a situation in which the pin threads covered by the nut have succumbed to corrosion. Essentially there are no threads on which the nut can advance to the exposed threads.

If the nut spins freely on the pin then there's a chance the ball joint will dislodge in the course of driving. The nut should keep it from coming off completely and the pin is probably nicely cold welded to the spinde, but over time it some play can build and cause noise over bumps.

BTDT - I just fixed that problem in a sway bar link in the Caravan that spent its first 100K miles in VA.

You should be able to borrow (AutoZone) or rent (anywhere else) a nut splitter. Or if you're really crafty, pry between the nut and the spindle as you turn the nut. You might get it to catch a good section of thread.

Sixto
95 S420
87 300SDL

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=40929

It's cheaper (perhaps in more ways than one ;))

hammer & chisel ??