Instability - is it normal(ish)

[Neophyte]

My '92 2.6 190 which has only got 98k on the clock with full merc history (verified) is unstable on the motorway. Merc last serviced it at 94k and I'd have hoped thaty'd spot something anything amiss? I seem to be often correcting (it seems not to happen all the time which made me think it was the wind) the windier the worse. But even if it is that it's still too much I think I'll firstly go for some laser-balancing. Really annoying. I think I saw a thread somewhere that said cars with a full tank are more stable (seems logical).
Am I being paranoid? I've recently read other posts that suggest changing the suspension bushes. This seems a bit excessive as I had a '92 Citroen ZX that was as stable as you could wish at speed. It never had any work done on the suspension in its life.

Any advice is welcomed.

Thanks

 

[SUE.]

Have your shock absorbers checked,they could be worn or leaking,this would cause it to be unstable.

 

[jonathanjhann]

jack the rear of the car up and check for play in the trailing arms, they are prone to wear!

 

[philharve]

Unstable?

Hi Neophyte

When you describe the 190 as being unstable, do you find the problem seems to get worse the faster you go?

You are probably finding that as you go faster the steering becomes lighter, more acute and the car's handling feels nervous, twitchy. Are you constantly correcting the direction of the car and do you feel that if you relax your concentration and grip the car would dart to one or other sides of the road?

If 'yes', it could be any one of a number of things. Much depends on whether the 190 exhibited these symptoms previously? If the car's stability has worsened it is probably due to a shift in the steering geometry or wheel alignment caused by wear parts or even misalignment or incorrect tyre pressures.

However, I have noticed this same behaviour in almost brand new hire cars barely a few weeks old. It is most unlikely that this is caused by wear. The answer may lay with the steering geometry or wheel alignment: a degree or two off will make a dramatic difference in handling and stability.

By all means have all wheels correctly align by laser as this will rule out some of the possible causes. Check all bushes too as weaknesses here will amplify the instability. How does the steering feel, taught and precise or a little loose and vague?

If this were a new car I would include one more item. I have encountered new vehicles in which the steering becomes sharper the faster you go. This behaviour is not to my taste but rally drivers will feel very much at home in such a vehicle. They describe these as 'drivers cars'.

REGARDS Phil

 

[stwat]

This could be your steering box that needs adjusting to take the play out. Id also have a look at your steering damper. I replaced mine not so long ago and it transformed my steering from being vague and wandering to feeling nice and tight and much more direct.

Stu

 

[Neophyte]

Thanks!

Cheers everyone. I had a nice blast on an open road last night and things werent too bad. I know that high speeds will appear to increase the reaction of the car as y'are moving along, but what it really feels like is the effect you get if buffetted by very strong winds. It's not overly dangerous as I'm aware of it now. It's only really noticeable above 85mph. I'm going to have a look see at all the bits and bobs you wise folk have suggested...

Thanks again!

PS - I really love the car and in no way regret getting her! Does anyone else think that the 190 2.6 is quick? I think it goes like a rocket and makes the sweetest of sounds!

 

[philharve]

Hello Neophyte

Did you resolve your handling problem? My car behaves exactly the same and the 'buffeting' suddenly appears around 80 - 90 mph. I daren't risk doing a 100+ because of the fear of losing control.

The steering feels fine. It's just that I have a nagging feeling that the back end is occassionally stepping out of alignment necessitating frequent course corrections.

A colleague has suggested it could be incorrect tyre pressures or worn tyres.

REGARDS Phil

 

[blassberg]

i was thinking tyres as contributing.

do you have a recommended tyre pressure for higher speeds / loads?

see it that makes a difference?

 

[tom7035]

My W124 200E with 130k sits the road like a leech at any speed (at least it did when the gearbox was working!) so I think you must have an error somewhere. Did anyone mention rear control arms/bushes?

 

[orbitalegg]

could be something as simple as under inflated tires or wheel balancing i would check that out first i know it sounds obvious but we tend to suspect the worst and its not always .

 

[Neophyte]

unstable at speed

Cheers guys. Sorry for the tardiness of my response - I kinda forgot about the thread!
Keeping the tyre pressure right does make much more of a difference than I'd ever thought. It's lovely when it's a simple thing! It aint perfect though and my mechanical skills are pretty abysmal - but I couldnt find play anywhere. I've yet to get the tracking/balancing checked/done - I hope to do that after my next payday!

I've also noticed a kinda hissing/escaping gas noise when i go over speed bumps - I presume it's coming from the shocks. I get the distinct feeling that a new set of shocks should be on my shopping list... ?

 

[philharve]

I have been investigating the 'instability at speed' issue and correct tyre pressures plays a significant part. I have experimented with different tyre pressures and deliberately under inflated each tyre in turn to see what effect it had on the driving experience. I soon learned that correct tyre pressures is vitally important. Under inflation results in vibration, steering irregularities and the suspension associated with an under inflated tyre tends to crash when striking road imperfections such as potholes. That's to be expected.

I still haven't driven my car over 100mph because it exibits an edginess or nervousness despite correctly inflated tyres. I suspect make of tyre may also be a contributory factor but this factor is not so simple to experiment with unless you know a friendly tyre fitter.

My car is 5yr old and it is possible that some of the steering and suspension bushes may have become a little tired. However, I agree with other contributors, check your tyre pressures first, they can make a considerable difference to stability at speed.

There is also another possibility which I've now come to accept. My Merc' is no sports car despite the 'Sport' designation and it doesn't handle quite as well as my Toyota. On the other hand, the Toyota was not as comfortable or as quiet as the Merc'.

Whether one being an automatic (Merc') and the other a manual makes any difference, that's another variable.

I definitely feel I am driving a computer in the Merc' which I didn't experience with the Toyota. Maybe the host of electronic gizmos in the Merc' is responsible for the slightly twitchy ride? Good question.

REGARDS Phil

 

[turnipsock]

When I first got my 230TE, it was all over the road. I replaced the steering damper and played around with the adjustment on the steering box which improved things dramatically.

I then discovered that one of the wheel bearing was worn and needed replacing. I replaced both wheel bearings as they were very cheap and easy to replace.

Have you tried jacking up the car and checking to see if there is any abnormal movement in the wheels?

My latest repair was changing the four rubber mounts that hold the rear axle to the car. The car would suddenly take a wild swerve when cornerning because of the movement in the mounts. The car is now really stable when cornering.

 

[shrekky]

hi neophyte,i own a 190 and can tell you the 4 bushes on the rear sub-frame are prone to wearing alot..........my local stealership (which are actually pretty good) told me ,on older cars,these bushes need changing every 2-3 years......depending on useage and milage.
The symptoms my car displayed were alot like what you describe and also,if you were travelling on a motorway at speed and came to a dip in the road that made the car sit down,it used to squirm at the rear.another classic symptom but not always present as was my case,is a knocking as you accelerate and deccelerate.
Said that another thing that can cause rear end wander as i recently found out,is a worn bush between the bottom arm and the rear wheel assembly,and there wasnt any play i could feel,and sat on the road the bush looked like it was sitting in the right place,wasn't until i jacked it right up,so the suspension was at full reach i noticed it,did orginally want to check out rear mount bushes thinking geeeessssshhhh they cant need replacing already !!,if this is the case i would inspect the stabiliser arms as well because when the bottom bush goes it really stresses this arms out and can cause them to wear fast.
So to save myself some time i replaced 2 stabiliser arms and bottom bush on both sides,she as stable as a rock again

 

[philharve]

Hi All

I've just replaced all four tyres on my Mercedes and the handling, especially roadholding, is much improved. My guess is that the better grip of the new tyres (Toyo Proxes T1R) make for a more stable ride. The directional qualities and the braking are superior to that given by the Continentals that previously adorned my car. The ride is definitely smoother and quieter.

I still can't be certain the there aren't suspension bush or damper problems but I'll deal with them at the next (100k miles) service.

REGARDS Phil

 

[concord]

Hi All
Having read the thread about the wondering problem on motorways, over 70mph, my car have the same symptoms. I dare not drive over 90 as it does not feel safe! I had it checked out by Merc dealers in Beconsfield. they put it on the ramp and checked the underside. also test drove it. The tech. said he could not find anything wrong with the steering and suspension including the steering damper. the damper has been replaced few months ago by the previous owner.

They did say however that the replacement shocks could be a remedy.
at the cost of £500+vat. - ouuuch

So the cause of the waondering on mine still remains a mistry.

Regards
Majid

C200, W reg, 2000, 85K miles

 

[angus falconer]

I seem to be often correcting (it seems not to happen all the time which made me think it was the wind) the windier the worse./QUOTE]

I had this on my last C43 and it turned out to be worn lower ball joints and worn steering damper. Changed them and it was back to normal.

 

[philharve]

I seem to be often correcting (it seems not to happen all the time which made me think it was the wind) the windier the worse./QUOTE]

I had this on my last C43 and it turned out to be worn lower ball joints and worn steering damper. Changed them and it was back to normal.

Hi Angus, Neophyte

My Merc' passed its MOT recently but there were a couple of 'advisorys': a worn lower ball joint and the steering damper was leaking. I was advised they would need attention before the next MOT but I won't leave it that long. They'll probably receive attention in the next week or two.

My Merc' exhibits the 'wandering at speed' phenomina and I, too, wouldn't risk pushing it well beyond the legal limit. I always thought the Merc' was tail happy but I'm now wondering whether the ball joint and steering damper could produce the wandering effect? The Merc' feels fine up to around 90mph but after that I seem to be constantly correcting the steering.

REGARDS Phil

 

[Bolide]

Wandering Mercs

In my experience the shockers are the last things to look at. Depending on model, if you have a Merc that wanders around, I'd look at the following:

* worn rear track control arms
* tyres
* 4-wheel alignment
* worn front arb bushes
* worn front balljoints
* broken front springs
* play in steering box
* worn steering idler
* steering damper

Nick Froome
www.w124.co.uk

 

[turnipsock]

Since my last post on this thread, I have replaced the lower ball joints on my 230TE. It's driving really well now, it's scarey how good it is for 180,000 miles. I'm still cornering faster than a lot of people on the slip roads and the roundabouts.