c-class steering woes

[silversixx]

I've read a lot online on various MB forums about steering, and cannot find a post which covers what I'm experiencing with my '96 C36 AMG.

If you're on a super-smooth road surface then it's hard to tell that anything is wrong: the car goes in a straight line and if you stand on the brakes it pulls up in a straight line.

However, if I'm on a road which has had some work done to it (for example, if a channel has been cut out to lay/repair something under the road and then filled in), it's all I can do to keep the car pointing straight. When a wheel touches any imperfection in the road, the car darts either to the left or the right and I have to 'catch' this with the steering wheel. The problem is getting steadily worse. If i hold the wheel at 'ten to two' when going straight-ahead then I often have to steer to 'quarter past one' or 'quarter to eleven' just to keep the thing pointing straight if the wheels find a raised/lowered section of the road surface. At speed, for some reason the problem is barely noticeable (but still there) - but at pedestrian speeds it feels like a 'clown car' - wanting to go wherever the faintest road-imperfection points it. Now, if I need to brake whilst the car is shimmying over road-imperfections at low speed then it becomes a bit of a guessing game as to which way the car will want to dart next.

Obviously something is badly wrong. From the way the steering feels my educated guess would have been that one wheel was steering independantly to the other at times, however having inspected the steering there is no sign of any play whatsoever: ball joints (both new), idler arm, pitman arm etc....all appear to be completely intact and show no signs of play whatsoever.

Having established that all apears to be well underneath the car I turned to the steering box to see if it could proffer any clues as to what is slowly turning the car into a death-trap. This is a further cause of confusion to me: The only car I've had before with a steering box was a BMW, and the instructions were clearly to adjust the play out of the box with the steering on full lock either-way. Every advice I can find on Mercedes Benz's is to dial-out any play with the steering wheel set dead-ahead. The things is: dead-ahead there is no sign of any play in the steering at all - but at full lock there is almost 3 inches of play at the wheel! Steering around a car park for example, where you're likely to use full lock at some point, there is this sickening feeling as the steering wheel reaches full lock and you feel the wheels 'flop' over a few moments later 'on their own'. Horrible....

If anyone could offer me the benefit of their experience on these matters I'd be very much in your debt because this is seriously diluting my driving experience - not to mention starting to become unsafe.

Cheers,
Andy

 

[Number_Cruncher]

>>The things is: dead-ahead there is no sign of any play in the steering at all - but at full lock there is almost 3 inches of play at the wheel!

Yes, that's OK. Leave the steering box alone.

Does your car have a steering damper? If so, fit a new one - they're quite cheap and easy to fit.

 

[silversixx]

Thanks Number Cruncher, I'll do that today - they have the correct damper at GSF.

One thing though - I understand what the damper does, but can't see how this will stop me having to steer right-or-left just to keep the car going in a straight line when running over imperfections.

Nevertheless, on you recommendation I'm off right now to go and get the damper - will report back shortly!

Cheers,
Andy

 

[Number_Cruncher]

To go a little further,...

The BMW steering box advice is correct for most steering boxes. The logic being that most wear happens near straight ahead, and so, if you adjusted such a conventional steering box in the straight ahead position, you would run the danger of the box binding up as you turn.

However, MB steering boxes are designed differently (better IMO), and should become tighter at straight ahead - which is why you should adjust them there (or, more usually, leave them well alone)

Typically large steering angles are only used at low speeds (other than by drifting hooligans!), and so, precision at large steering angles isn't a priority for MB. However obtaining good precision on centre, where the car will spend most of it's time at speed is the aim.

The effect you're describing is sometimes called tramlining. It's usually more of a problem with wide wheels, and can vary between tyre brands.

My logic for suggesting the steering damper is that it can reduce the feedback of steering loads, and can help to resist this type of behaviour.

 

[silversixx]

Many thanks for that Cruncher,

I have the correct damper now and will nail it on after a bite of lunch.

I'm hoping that when I remove the old damper it has very little resistance left - and that the new one will help encourage the wheels to go where I point them. Will report back soon...

By the way, after my BMW experience I was against having another German car ever. I have to say that if I can get this and a couple of other minor niggles sorted then I might have been a bit hasty - the C36 seems to be a good piece of kit.


Andy

 

[silversixx]

Number Cruncher, you've called that one spot-on.

There is stil a very very faint sensation of 'tramlining', but the steering is dramatically better.

The damper I removed was completely 'lifeless' and needn't have been there!

Many thanks again.

Oh and by the way the damper was about £18.00 from GSF.

Andy

 

[Number_Cruncher]

I'm glad the damper has helped the situation - thanks for reporting back with good news! - they're so cheap and easy to fit, and are one of the few things I'm happy to replace almost as a matter of course rather than after diagnostic testing to make sure.

>>There is stil a very very faint sensation of 'tramlining', but the steering is dramatically better.

You *might* be able to tune this a little by making a subtle change in your tyre pressures. Depending upon how your current tyres are wearing, you *might* find an improvement with a couple of extra psi in both front and rear tyres.

The logic for suggesting this is to even the load across the tyre's width, and prevent the tyres switching from being loaded on one sidewall or the other. Suggesting upping both front and rears is to make sure the difference between the front and rear axle pressures remains the same, which should approximate maintaining the correct handling balance between front and rear axles. Upping the front axle pressures while leaving the rears the same is a change towards instability, which in a powerful car is doubly undesirable.

Don't go more than a few psi away from standard spec.

 

[BLK]

Have you checked the steering rack mounting bolts? I had an identical problem on a Vauxhall some time ago and after checking or changing virtually everything the problem remained. I checked the rack myself, obviously, but couldn't find any play in it, so I had the rack checked by the dealer who said it was fine and told me it was probably my wheels or tyres that were causing the problem. I had aftermarket alloys and tyres fitted to it, they were on when I bought it, so I bought a set of 4 factory standard wheels and tyres from ebay, and although it improved the ride substantionally it did not completely irradicate the problem.

With the new wheels and tyres on the problem felt more irritating than dangerous, and it eased it's way through an MOT, even AFTER I told the MOT tester that I thought there might be a problem with the steering, but he said it was OK.

I had several people look at it but no one actually managed to pinpoint the problem, so I reluctantly decided to 'put up' with it.

Some months later I was doing another job under the car and came accross a bolt that was seized solid. I used a long 'breaker bar' on it to get some extra purchase and when it released it did so quite suddenly which resulted in the handle end of the breaker bar geting wedged ender the steering rack, but amazingly, not my fingers! I gave the bar a tap with a hammer to release it and as it did I saw the steering rack move a couple of mm. So excited by this amazing discovery, I immediately gave the steering rack my full and undivided attention, but only to find there were no loose mounting bolts. Not content with the idea that my eyes played a trick on me, I got a crow bar on the steering rack and gave it a gentle push and tug and sure enough it moved again.

I zapped the mounting bolt with WD40 and then went to look up the torque setting. I set my torque wrench to the appropriate value and proceeded to tighten it but it reached torque without any movement. Feeling a little disheartened by this I took my breaker bar and proceeded to remove the mounting bolt. It didn't put up much of a fight and came out quite freely. The thread seemed OK, but the shoulder and flange seemed quite worn so I decided to replace it with a dealer supplied replacement. When I got the dealer they asked me if I wanted the 'spacer' too??? OMG!!! That was all that was wrong with my car... a small steel spacer that sat over the shoulder and up against the bolt flange, thus shortening the shoulder and effectively lengthening the thread to allow a tight and secure fixing. My steering was perfect after this and I replaced my after market alloys and all was well again.

I guess that whoever chose to replace the bolt without the spacer, (FOOL) didn't notice any ill effect, and to be honest neither did I at first, but after driving the car for a couple of months it started to become apparent. I'm guessing that the fault only became apparent after a period of wear on the bolt and mounting hole.

I have no idea if any of this is relevant to a Mercedes steering system as I have not had any steering problems with my Merc, (touch wood), but the problem I have described created identical symptems to those described by the thread author, so I just wondered if it might be adviseable to check all your mountings for movement/wear.

If you are still feeling "tramlining", however faint, it would suggest to me that the problem still exists but has been eliviated somewhat by a new damper.

 

[turbopete]

an amg model will have very wide and very low profile tyres. this means that in their very nature they are more susceptible to tramlining as there is less sidewall to flex to absorb the road imperfections! if any of you have teenage children with their own cars that have huge wheels on (like they all seem to now!) try a short drive in their car, you will see what i mean!

 

[kth286]

the maintenance schedule does indeed include checking for tightness, the three mounting bolts for the steering box (not a rack on this model) to the side wall.

So you might want to do that.

 

[philharve]

drag link idler bush and maybe real axle bushes

Hi silversixx

I have had a similar problem on my 2000 C class, a slight 'nervousness' in the straight ahead position. I have replaced most of the front suspension components, including the steering damper, but a trace of nervousness but is now well above the UK speed limit.

Upping the tyre pressures slightly, as suggested by Number_Cruncher, made a big improvement.

My indie said he will replace the steering drag link idler bush (cheap!) at the next service as wear in the bush can have adverse affects upon steering. He also mentioned replacing the rear axle bushes as wear here 'might' cause the rear axle to steer the car which then has to be compensated for by the driver. However, my indie warns he is reluctant to replace these bushes because the parts alone is GBP200+ and their replacement will necessitate a full geometry check (expensive!). He added he would prefer I wait until these bushes become an MOT advisory before replacing them. As long as I keep below 100mph it is not an issue.

REGARDS

Phil

 

[ianstaley]

wheel wander

Hi ther read this with a lot of interst, i own a W202 estate, with alloys, OEM. This merc has always been a bit sensative to wander at speed, tried evrything, even renewing bushes and so, I still havent fixed the problem fully under high side winds, but try the wheel bearings, they do need adjusting from time to time and its about a 20 minute job each side, take off the wheel, knock off the dust/grease cap there is a bolt with a scew in it, just undo it slightly turn the main bolt by hand (it will do so easy) untill there is no play but the hub turns without udue force, lock the grub scre, replace, problem solved. hope it helps. oh i dont know much about your car but mine is a 1997, C180 station wagon. 1800 cc automatic with 246000 Km on the clock, doesnt use any oil of note, just seems to want to go on forever. hope it helps.
Ian

 

[philharve]

Wheel bearings slackness cause of steering vagueness?

Hi ther read this with a lot of interst, i own a W202 estate, with alloys, OEM. This merc has always been a bit sensative to wander at speed, tried evrything, even renewing bushes and so, I still havent fixed the problem fully under high side winds, but try the wheel bearings, they do need adjusting from time to time and its about a 20 minute job each side, take off the wheel, knock off the dust/grease cap there is a bolt with a scew in it, just undo it slightly turn the main bolt by hand (it will do so easy) untill there is no play but the hub turns without udue force, lock the grub scre, replace, problem solved. hope it helps. oh i dont know much about your car but mine is a 1997, C180 station wagon. 1800 cc automatic with 246000 Km on the clock, doesnt use any oil of note, just seems to want to go on forever. hope it helps.
Ian

Hi Ian

I appreciate the point you are making and I have undertaken the task myself on other makes of vehicle. Curiously, my indie has never once mentioned adjusting the wheel bearings on my W202. The next time I see him I will enquire why. The answer might simply be that they don't need adjusting.

REGARDS

Phil