What would account for steering having difficulty returning to straight position?
 

As I continue to observe my power steering, I guess what I'm observing is as follows: The wheel turns fine when I'm turning INTO a turn. But when I relax my grip on the wheel having made the turn and want the wheel to straighten out, I notice that I'm having to turn the wheel back into the straight position....as opposed to its doing it (mainly) by itself.

My parts guy suggests steering damper. A forum member suggests pump or gearbox. What are anyone's thoughts? It's a 1991 300D.

Thanks.

When I have steering issues, its usually the alignment.

Lower ball joint seized. I've seen more than one.

If it were a ball joint, wouldn't I hear something (like typical ball joint creaking)? Or not necessarily?

In general, caster gives the steering its tendency to return to straight ahead. I go with those who suggest component wear or binding resists the self-centering force if it developed over time. Most MBs of that vintage should have the wheels aligned with the steering box locked. Too many shops align to the steering wheel which might have been repositioned during a previous alignment or other repair.

Sixto
87 300D

A binding ball joint probably won't bind with the front wheels off the ground but a steering gear or damper will. Don't count on a ball joint to make noise. Check for stiffness when returning to center with the front axle off the ground with the engine running and not running because a hydraulic issue in the gear could cause this in addition to gear mesh being adjusted too tight.

Caster does affect return-ability to center. More caster means more tendency to stay on center. 123's and 124's are spec'd with so much caster that the caster angles would have to be a mile off for return-ability to become an issue.

your car needs a correct mercedes alignment done with steering box lock and spreader bar on the wheels. The alignment on W124 seems voodoo to some sears type shops - change one setting and something else goes out.

I learned about steering issues on a diesel ram. Steering threads for those trucks are surpassed only by cracked dash and injection pump threads. Return to center issues can be either hardware or adjustment. The only way to differentiate is to go through the hardware then adjust. The $8/hr monkeys assigned to the machines can't think outside of the box & usually don't understand how the variables relate.

I never ask for an alignment. Instead, I say that the vehicle is doing xxx & ask them to diagnose and price the repairs. If they diagnose alignment as the problem, I won't pay unless it fixes the problem. In other words, buy the hole, not the drill bit.

What kind of container do I need to transport the hole when taking it home ?

I agree with that.... but sometimes it is easy to just set the toe in... that by itself can produce this symptom...

You need at least a 1 ton 4x4 straight shift - diesel of course, preferably with Cummins 12V. Anything else may have trouble climbing the hills.

One can set toe with strings, jack stands & propre drill bit used as a feeler gauge. Good enough for Gubmt work but better used when you know everything is in good shape else you'll be questioning your toe setting.

I opt for lifetime Firestone alignments so I can use their machine frequently with impunity.

I have seen an improperly adjusted steering box cause this too.

X2
An over tight steering box will do this.
Why was it over tightened? Normally because the worm is worn in the straight position & been tightened. when it is away from straight it is too tight.
I lean towards the castor being out being the more likely cause. Positive camber can also reduce return.

I agree. And with that said we do not have the information letting us know if an attempt was made to adjust it prior to the issue.

By way of an update, my indie is looking at it right now and is a bit perplexed. He says it looks like the steering box has never been adjusted....still has factory paint. Says all suspension components look good. Pump is fine. I think next he's going to look at the steering damper.

He doesn't do alignments, so if he continues to be stumped I think I'll get it aligned somewhere else and then see where things stand.