w123 Steering dead spot, still - after much work
 

Hi all-

I bought a very nice '84 300D a month ago. It had what felt like a 5-10 degree "dead spot" in its steering. When driving on a straight-away, I had to move the steering wheel 5-10 degrees from side to side to make minor directional corrections. It had a very disconnected steering feel. At any speed above 20 MPH, I could illustrate this problem by jiggling the wheel inthat 5-10 degree range without any effect on the car's wheels.

Following much research on this board, it sounded to me like the problem was the idler arm bushing and/or generallt worn front end parts, and that simply tightening the steering box would help.

I took the car to a well-known and respected Mercedes mechanic. He said it appeared as if the car had been tied down to a flatbed by the control arms, which were slightly bent.

The receipt says the following (excluding some other work he did):
Replace Idler arm bushings
Replace both lower ball joints, both caster supports, replace both tie rods
Align front end
Steering PCAT (?)
Adjust steering box

On the parts list, I see (among others):
2x Tie Rod
2x Steering Joint
1x Steering arm

After the repairs, the steering was improved. However, there's still about 3-5 degrees of play. It's starting to get annoying. Another symptom is that if I let the wheel go, the car will very slowly drift left or right, depending on the conditions.
The play is exceptionally annoying during some turns, like on the highway. If I am taking a broad right turn followed by a smaller left turn, that play allows the wheels to go too far to the left, which means I then have to overcorrect to get back on track.

Any ideas? I'd like to take the car back to the mechanic before too much more time elapses. Whunter suggested in another thread that the guide rod mounts might need to be replaced. I'm willing to pay the mechanic to do the work. I just want it fixed! If it's gonna take a new steering box, that's fine, just let me know!

Thanks for all your help!

I have the same issue on my 300SD (84-126)
I think it is the steering box on mine, because even when the box is adjusted to specs I have the play. Depending on how the box it adjusted I feel the end of the dead play zone hard or soft. I perfer the soft feel but I hate the free play. The manual indicates that one inch of play at the steeering wheel is normal. However this is the far end of normal and as you indicate annoying.
I have replaced many of the parts that you have and have been told all the other parts are OK.
I am curious as to what others say, replacing the gear box is not a cheap endevour.
Your drift is probably normal, depending on the crown of the road. When these MB's are aligned to specs this is a common event.

Thre is more to adjusting a steering box than turning that hex nut till it gets tight, the FSM lists several tools and a specific procedure I somehow doubt most shops follow.

I'd want to talk a good bit with anyone rebuilding these before I purchased one, or had it installed.

I agree, my car only has 145K on it and so I am hard pressed to believe the box is worn out.
Any MB mechanics out there that can shed some light on these old steering mechanisms.

STEERING PLAY
 

I know I have a different car, but with my w126 I had developed a pretty bad steering leak. It had gotten pretty bad after about 117k. I purchased a salvaged steering box, $150 compared to $575 new, so I went with it. After installation, I noticed a slight play in the wheel. I have asked the dealership about tightening the box and they advised they quit adjusting them because of all the problems in the boxes when attempting to adjust. I guess in my situation, the play is better than the leak. My opinion is that the gear inside the box is worn some and the only way to fix is to replace with a new box. Hope this helps.

The manual says that?!?!? That's wacky.

When I first talked to the mechanic (Sig at MBI Motors in Portland, a real nice guy who helped me pick the right MBZ to buy) about the problem, his first response was "Have you ever driven a Mercedes before, son?" :) I chuckled and said no, but that I didn't think that kind of play was normal or safe, for that matter.

Since this really only seems to be detectable at speeds about 20-25 MPH, how would one tell if the steering box is bad while parked or on a lift?

How much labor is involved in replacing the steering box?

Thanks!

Does anyone know if there is a rebuild kit for the steering box that might fix this problem?

Hello,
For what it's worth, from the Ponton factory manual(translated from German): 15 to 25mm of freeplay measured at steering wheel rim is acceptable. The later cars with manual or power assisted steering only list the 25mm(1 inch) maximum. I would therefore take 15mm as the minimum(?)
The actual adjustment is a FRICTION adjusment with the box removed from the chassis and bolted to a fixture. I agree with the tech as many drivers that have been driving front wheel drive cars with rack and pinion steering will find a Mercedes steering vague and the car difficult to control in a fast corner.
Before attacking the box to make adjustments or to replace it, check the steering column bearings and the steering coupling, a hard rubber disc in a W123 and strange metal/plastic bush assembly in W107/108/109/110/111/112/113/114/115/116, these things do wear out after 20-30years.
Have a good week.

One often overlooked part on 123's that will cause them to be loose as hell is the upper a arms. The feeling is more one of understeer going in with a "rollover" into normal steering. However, the transistion is a bit abrupt. The bonus is they are cheaper and easier to install than a steering gearbox.




Joe

just for fun...

this "free play" drove me so nutty that my dad and i put in rack and pinion this winter. well see how much better it is this spring/summer. (i did compromise my turning radius...but i can deal with that for a crisp steering car)

(the whole front end was tore out, rebuilt with all new rubber, parts, and blasted, cleaned restored arms, ect...still had play in the steering after all of that work)

Jake

You are certainly right about that, all front and rear suspension components and bushes should be check out and replaced BEFORE fiddling with the steering box adjuster. A cheapskate here with a 300SE always complained about instability turning into curves at 70mph+, the rear subframe bushes were softer than jello because he had been *lubricating* them with WD-40!
My W115 has dried out front subframe and suspension bushes and steers *different* from left to right but at least I am not trying to destroy a good steering box by tightening up the adjuster.

steering wheel play
 

There is a normal/acceptable steering wheel play in all the
1977-85 w123 diesel and w126 diesel up to 1986,if it is not
more then 1 inch(2cm) on both sides of the steering wheel,
I would not recommend any adjustments if the play in the steering wheel does not exceed that,take it from me,I might not
be familiar with the newer MB...I have owned 184 old models
(w123/w126 diesel),thats how I put myself thru college...buying
and selling 2-5/month,they all have the same problem,except
if the front end and steering box was recently replaced,you have
to adjust your driving style.

i own a few of those cars, and almost everone i bought had massive freeplay in the steering. i almost always found the upper
control arms blown out causing to car to wander.
as far as the sloppy steering....
did you turn the steering wheel to the left or right stop position while adjusting the hex adjuster nut? i heard from an oldtimer thats the properway.
if the tech "inspected" the whole front end suspension and say that the rubber joints in the steering shaft are in good condition.
me personally, i would replace the p/s gearbox with a exchange unit.
www.meridianautoparts.com
check this place out
good luck

Had the same problem with my box. Had the typical 'adjustment' made and it did VERY little except to 'stiffen' the steering feel. 'Dead zone' still there.

After that, I learned that this adjustment nut that everyone messes with is the wrong way to go. Apparently, it _does_ tighten the steering but actually does nothing as far as removing the dead zone in the steering. My suspicion is that the new stiffness either mask or fools people into thinking that the freeplay is reduced.

As noted, there is an an actual MBZ procedure that involves removing the box and performing some ridiculous adjustment. My indy said that the procedure appeared to be little more than something the engineers cobbled together _just_ to have something to put in the books due to his perception of what the procedure really accomplished.

My indy has built a jig of his own design that he uses for making the adjustment. It does involve removing the box. After having this done, my free play went from ~2-3 in. down to at most .5 in. (if even that much). IOW, the free play is pretty much GONE. It wasn't cheap to have done (much less than a new box tho), but the freeplay was driving me INSANE and I'd already pretty much rebuilt the entire suspension trying to fix the free play issue.

.

Having owned three 124 cars and a 126 and adjusted all of these for steering play, I learned quite a bit:

-Sometimes the box is simply worn out
-When adjusting the box, you can over tighten, crush the mechanism resulting in a worthless box (Don’t ask me how)
-Adjust slowly and avoid the binding/ over-tightened result at all costs. (the steering does not self-center itself when driving around normally).
-I was told to adjust with the wheels off the ground. I did not ever determine why this was necessary but it did seem to help.

On the old 79 240D, I did replace the box after checking out several used boxes at a junkyard. Also, the later boxes do seem to be better and the adjustment goes easier.

Although all these series cars have free play, I was able to resolve the free play issue to an imperceptible / acceptable range.

Hope this helps,

Haasman