Knocking front front when going over pumps

[Nightdriver]

His problem has so far cost me £900 in new bushes ball joints control arms, etc etc but the damn knocking sound is still there.
It only happens going over speed bumps, pot holes or very uneven surfaces particularly when turning steering wheel to left.
It sound like it knock on the descent like something is springing back up when car lands after going over bumps, it's dull thump I can almost feel it beneath me. Ani ideas?

 

[Swotty]

I have this problem with my jaguar XKR. Put it up on a lift yesterday and found it was an upper wishbone bush.

Just a thought.

Stuart

 

[Merc Owner 2B]

Sometimes the quickest, cheapest way to diagnose is to take it for an MOT or ask an obliging test centre to do you a short uncertificated test

 

[brucemillar]

Had this on my C55 Estate. It was the N/S front shock top mount that was loose (not falling off loose) but not spanner tight.

 

[Nightdriver]

Mot centres have failed to find it, they claim car is too heavy to check manually. They check what they can, bearings, ball joints tracking arm, look for moving/shaking parts around the wheel etc but no joy.
The wishbone is one example they can not get any movement by using say a crow bar or whatever they call em, so will not know if it is this without actually changing it, apparently it's not cheap.

 

[Nightdriver]

Apparently this model does not have a top mount for shocks??? I have had some disagreement between mechanics on this.

 

[BlackC55]

It doesn't really have a top mount as such.

I expect the knock is in the shock itself. Very difficult to prove though.

 

[grober]

Steering rack mounts or the rack itself?

 

[Swotty]

To check the wishbone bushes/joints, put the car on a lift, jack up the front until the wheel is clear of the ramp and lever a crowbar under the front tyre. You will hear and feel any movement in the wheel - and, from underneath, be able to see movement . Any garage can do that.

May not be the problem, but worth eliminating before replacing other parts first. It surprised me - I suspected the anti-roll bar bushes or drop links.

S.

 

[grober]

To check the wishbone bushes/joints, put the car on a lift, jack up the front until the wheel is clear of the ramp and lever a crowbar under the front tyre. You will hear and feel any movement in the wheel - and, from underneath, be able to see movement . Any garage can do that.

May not be the problem, but worth eliminating before replacing other parts first. It surprised me - I suspected the anti-roll bar bushes or drop links.

S.

Good call on the roll bar or more likely the drop links--- I had assumed this would have been the first thing they checked. But always dangerous to make assumptions.

 

[m2mb]

I changed a few suspension joints, bushings, cups. The vibrations are still there. Shocks are prime suspects. MOT confirmed one of them shot but dix not get around to change them.

 

[SL350_SWINDON]

I raised the same question yesterday and got zero replies from the forum.

 

[Paddcomp]

I have the same issue with my e class, s211. See my thread on front suspension clunking, between us I'm sure we'll change a full front end.

 

[Nightdriver]

To check the wishbone bushes/joints, put the car on a lift, jack up the front until the wheel is clear of the ramp and lever a crowbar under the front tyre. You will hear and feel any movement in the wheel - and, from underneath, be able to see movement . Any garage can do that. May not be the problem, but worth eliminating before replacing other parts first. It surprised me - I suspected the anti-roll bar bushes or drop links. S.

thanks the anti role bar bushes have been changed. I haven't changed the drop links? Is that also called anti-role bar linkage arm ? It was suggested but they look solid and in tact.

 

[Swotty]

thanks the anti role bar bushes have been changed. I haven't changed the drop links? Is that also called anti-role bar linkage arm ? It was suggested but they look solid and in tact.

Yes, those ........ but if they look and feel O.K., it's probably not them - but they are inexpensive to change. Have you checked out the wishbone bushes/ball joints?

Stuart

 

[grober]

thanks the anti role bar bushes have been changed. I haven't changed the drop links? Is that also called anti-role bar linkage arm ? It was suggested but they look solid and in tact.

The drop links tend to go at the ball joint/s where excessive play gives rise to a knocking noise going over bumps. Play can sometimes be discerned visually or by rocking the static car on its suspension while cupping your hand over the ball joint- you will feel any play- be careful not to get your hand or arm trapped anywhere while doing this. Its a two man job- one hefty bloke to rock the car the other to check the suspension.

 

[Marku]

Had exactly that noise on two vehicles and it was really annoying. Never solved it on the first as it was sold but on the second it was the front anti-roll bar bushes. The bushes may not be that expensive but having MB fit them was.

 

[Nightdriver]

I had the ball joint changed on the other side n/s due to a crunching noise when going over speed bumps. Garage found play in the joint) after £300 spent (240 on the part alone) it still did it, so up it went again. The crunching noise was the bushes on the antiroll bar, a bit of grease on the rubbers and it's gone. So why did I spend £300 on a part that was not the problem oh and it's a special order from Mercedes none returnable!

 

[Nightdriver]

But on the not so bright side, I think I found the cause of the knocking. It seems to be coming from the steering rack, when I punch it on o/s it knocks but not on the n/s. (mercedes only) quote for steering rack wait for it....£1230 +vat + fitting. I think I must now embrace the knocking and learn to live with it.

 

[paul73mt]

i had this when i first got mine and as it was still under warrenty i let MB look at it only to be told 'yes it does make a noise check 5 more cars on site and they done it also'