So here's my question: if it's not the damper (just replaced it) and it's not the alignment (we'll know soon enough), what could it be? If, when the damper is removed, the self-centering problem goes away, that would seem to indicated that something else is binding, but to such an extent that it's only symptomatic when the damper is installed.

What are some possible/likely candidates as to something else that's binding?

X2 on the ball joint... Mine broke off in the grocery store parking lot this past Friday. Had the same symptoms.

Hmmmm......I have wondered about ball joints (mine are original). About a year ago, I heard what sounded like ball joint creaking. But it went away. I took it to my indie anyway and he indicated that they were fine. He essentially had a blank check to repair them but said they were OK. I have not heard the noise since. But now I wonder....

Based on what everyone is saying, it could be most anything. But I would recommend having your indie (or someone you trust) re-check the ball joints just to be sure. Broken ball joints can ruin your day. See your other thread about ball joints.

That does make sense. This is really frustrating. I wonder if the ball joints can LOOK and FEEL fine, but nonetheless be causing a problem with the steering. When the steering damper is removed, the problem goes away. But it is NOT the steering damper; I just replaced it.

On two different occasions, my indie has looked at my ball joints; on both occasions, I've gotten a clean bill of health. I wonder if I should just replaced them on the ground that they're 20 yrs. old.

I was all set to take it to the dealer....I think I'll back out of that.

Yup, I discovered that this summer when my '79 wagon lurched over on a steep uphill curve and the car dragged to a halt as I quickly found a place to "pull over" ha! :eek::eek::eek::eek:
The RF wheel was cocked sideways, at about a 45 degree angle. Luckily there was no other traffic on the 2 lane road and it was a place that cars could pass without endangering each other.

The ball joint had been groaning, telling me hey! replace this thing before it kills you !!!
DDH

An update: had an alignment done at a local alignment shop. My theory was that, even if they couldn't do it perfectly due to the lack of a spacer bar, they should be able to get it close enough to reveal whether the alignment was the cause of the problem. Unfortunately, the self-centering problem persists.

While it's possible that the problem is still related to alignment and that I'll have to get the dealer to do it, my current suspicion is that there's something in the steering system that is binding. My next stop, wanting at all costs to avoid the dealer if possible, is the best independent MB tech in the area....it's a bit of a drive which is why I don't usually go to him.

That's all for now.

Yes, they can.

That's what I'm betting on, then.

Disconnect the drag arm from the pitman arm. It could easily be a steering box where an owner overtorqued the adjustment in an attempt to cover slop. Does the adjustment screw area look like it has been bothered before?

This enables you to move the steering parts from side to side to attempt to identify or establish if there is a bind somewhere else as well. Changing parts just on suspicion usually is not too productive.

Adjustment screw has never been touched....still has factory paint.

I do not see how the independant mechanic could have determined if you had a seized ball joint or whatever with the pitman arm hooked up to the linkage. By nature a seized ball joint or tie rod end type of joint will usually test tight. Even tie rod ends and others can seize remember.

With the disconnection you can find it if it is there. With the wheels off the ground the system should traverse fairly easy without the steering box hooked up. If not close observation might identify the fault. Technically even if the steering box has not actually been adjusted it may have a form of failure as well. This you would notice when it was disconnected .Hard to turn. It is simply a divide and hopefully conquer method as well.

If the alignment shop gave you a printout you want to see if the castor angles where not a long way off what they should be. They are the principal drivers of aiding the return centering. Adjusting the lower bars length determines the castor. Again on many newer cars the only real adjustment left for alignment shops is basically the toe in unless they change parts. The three axis adjustments are still there on mercedes older cars.

Since many alignment guys do not deal with castor on newer cars he may not understand this. For example if someone changed those two bars at one time and did not adjust them properly could do it but the car would have a difficult time steering straight requiring too many corrections constantly if way off.

So if you know the recommended castor check it against his printout. I noticed even my alignment guy ignored the castor readings on his machine. Technically one side was out enough it should have been corrected. I suspected he did not realise that mercedes had an adjustment for it. Or was just too lazy to do it.

In terms of the indie inspection, I'm beginning to suspect that he too quickly concluded it was an alignment issue....although it still may be.

I don't have a high degree of confidence in the alignment....caster angle is 9.8 left and 10.7 right both before and after, both within range I'm not even sure they did or could adjust it. But in fairness to them, they acknowledged at the outset that they weren't confident that they could do it exactly as it needed to be done.

But it seems like disconnecting things is certainly in order.

Here's a scary story: in researching this, I talked to a first-rate MB tech in PA (Fred's Foreign Cars in Kennett Square). When I told him I was becoming more and more suspicious of the ball joints, he said one time he had his daughter's car....he had looked at the ball joints and they seemed fine. He was driving down an alley at 5 mph and one completely fell apart. So he, even as an experienced professional, missed it...thankfully he was only going 5 mph.

the way I see it is you have either a :

- steering box failure
- ball joint / suspension aged too much

I dont see an easy or inexpensive way to diagnose this from here - the springs have to be compressed and removed and the UCA needs to be released from the spindle. Then you could really feel the lower ball joint and see if it is seized, or loose or what have you.

At that juncture, you might as well replaced the lower ball joint and everything else around that looks worn, whether it is showing signs of wear or not.

I believe lower ball joints are 3 hours of time at the shop each.