Greetings,

I'm new here and I come from little country called Croatia in Europe, so pardon my English if it's bad, especially on forums such as this, where I'll probably lack many words to describe my problem.

For the last 1 year, I've been trying to solve this problem and couldn't.
A year ago, I had a good deal and purchased a used 2004 Mercedes C-class W203 (270CDI).
Since then, I spent around $3000-$4000 on servicing that car, changing worn out parts, making it as close to "new" as possible.
The servicing was all done in a local Mercedes-Benz service (not authorized but pretty good one, recommended by many).

So, I changed many parts but one problem persists.
I've been hearing this damped knocking/rumbling noise under braking for a year now and it's now starting to overfill my cup.

It's really like this:
It sticks my nerves every time I press that brake pedal, little by little.
It's coming from the front, under light and heavy braking, especially when going over bumps or other irregularities on the road.
It's also audible while braking+turning the wheel at either direction, for example when you want to do a 180 after the traffic light or so.

It's also audible when going in reverse and turning the wheel.

One thing that I found interesting about this noise is that it somewhat reduces after some time spent driving the car and using brakes. In my modest understanding of our Universe, I'd say it reacts to heat, because it's most apparent early in the morning when starting cold, and least apparent after I spent some time driving the car and using the brakes heavily. Maybe something that contracts and expands?

Anyway, I've been reporting this noise to the service staff several times now (probably >6), they'd always try to look it up, reproduce, and ultimately fail to hear it.
I've been driving them around, and while I'd hear the noise, they wouldn't.
I've been giving them the keys so that they could drive around and hear for themselves, but they wouldn't succeed to.
They probably think I'm nuts or something.

Finally, a few days ago I had to change front discs and pads.
One guy took my car for a ride and said that he can hear the noise - imagine my enthusiasm...
He blamed one of the ball joints (front lower left).

It's this thing:


I was relieved thinking he finally found the culprit, only to be utterly disappointed when I picked up my car the next day and took it for a ride home.
Yes, the noise is still there.

I'll go back there tomorrow and complain, but there's probably nothing they will be able to do.
I won't ask for money back because the previous ball joint really was worn out and needed changing, but it didn't solve this particular noise which is driving me crazy.

I'm thinking of mounting a GoPro camera underneath the car, maybe it will pick up where the noise is coming from, don't know what else to do.

Maybe you have an idea ?

The undercarriage is now, according to them, like new.
There's no gaps, movements (they tested with pry bar), leakages, discs are new, pads are new, all 4 shock absorbers new, all 4 shock absorber mounts are new too, all engine and transmission mounts new, etc., etc. - I could go on with the list.
The steering wheel was checked too.
All fluids are new, too.
Don't know what else to say.

Thanks for taking the time to read, I appreciate it

 

I might have investigated the ball joints as your mechanic did, they do wear out frequently, especially since the roads in Croatia are not glass smooth.

Since you report a suspicion concerning temperature I would be looking at the struts. Just because the shocks are new does not mean they good. There might also be a problem with the spring retainers. For some reason the upper strut bearing mounting and torque settings baffle some mechanics. This can cause clunks as well has a brake rotor that has excessive run out. I have seen cars that had a poorly installed brake pad anti-rattle spring cause clunks while braking.

Your English is fine. Everyone can understand the way you write.

 

Thanks for your reply.
So, you suggest that next time I go to the mechanic I tell them to inspect:
- all other ball joints
- struts
- spring retainers
- brake pad anti-rattle springs ?

Would you just mind showing me a pic of struts and spring retainers from google or so, since I'm unsure whether it's the same thing I'm looking at.

Thanks!

EDIT: Just remembered one important thing that I forgot to mention...when this noise starts happening, I can also feel gentle bumps (really gentle) on my feet, whether they're on the brake pedal or on the floor.

 

Sounds like ball joints to me as I have had that issue many times now sadly... Make sure to use genuine/OES parts as the cheaper ones will fail sooner than they should.

 

Do you perhaps remember how much did you pay for a control arm ?
I paid around €110 ($150) for one control arm (front lower left).

Then this deal is not good or suspicious?

 

LEMFOERDER arms are about $130 and unless you want a Mercedes one that is the only one I would buy (Mercedes ones are made by LEMFOERDER)

 

Did you replace all four control arms? I replaced my upper control arms first when I did the struts, but I didn't get rid of my knocking-while-braking noise until had replaced the lower control arms as well. Then it went away.

Of course i also replaced the sway bar links.

And I still have a slight knocking in the steering linkage ... not sure if it's an inner tie rod ball join or something loose in the pinion gear. It's a very small amount of movement and I only hear/feel it when I go over a bump in the road, such as backing out of the driveway in the morning.

 

If your castor bushes, sway links & bushes & ball joints are all OK & struts are OK.

Make sure that the rack mounting bolts are tight & rack bushings are OK.

 

Had the same problem once a while back. Check all your ball joints. I had my outer tie rods changed (both sides) on the advice of a mechanic, which didn't solve the problem. Went to a 2nd mechanic who found a failed ball joint upon closer inspection. Part replaced. Problem solved. Unfortunately I couldn't remember which arm, except it was silver (like the one in the pic) and not black.

The way he located the problem - hoist the front of the car, then shake each wheel by grabbing and violently pulling/pushing at the 3 and 9 o'clock positions. You can see which ball joint has play.

 

I should also mention, when I had the knocking noise before changing out my control arms, nothing under the car seemed loose. I guess that's why they say to test out teh car joints with a crowbar.

Another note on bushings -- they may look fine when they aren't. My rear tranny mount had collapsed ... but "collapsed" meant that the rubber was old and was allowing the mount to stretch a bit more than it should. There was no visible torn rubber. Even when I replaced the mount, the new mount seemed to sit almost as low as the old one, maybe 1/8" to 1/4" higher in the yoke. But that was enough -- noise gone.

So my rule of thumb on these cars -- after several years start replacing rubber

 

I was at friend's workshop yesterday.
He's a meticulous person in general, so we spent a good amount of time checking all components.
It is sad that he found something that certified Mercedes service didn't.
He found a damaged bushing on one stabilizer coupling rod and play between left inner tie rod and steering gear. I didn't even tell him that noise comes from front left end, he found it himself.

In regards to ball joints of control arms, we checked them all with a crowbar and they seem to be OK (from the outside and by the amount of play), but who knows, maybe they're damaged inside, which we can't see until we dismantle them - I'm still weighing about doing that.
We also shook all the wheel with hands in position 3 and 9, then 12 and 6, and so on.

Anyway, he has exclusive prices on all Mercedes parts so I might just change all that and be done with it already.

 

I like the car well enough, and I save enough money from DIY'ing, that I'm fine with refreshing the entire front suspension once every several years. I have 110k miles on mine and for the most part it still drives like new, and feels better than most other cars I get behind the wheel of.

 

Definitely, the car feels more like cruiser/tank in comparison with other cars, I love driving it, it relaxes me.
Mine has 125k miles now, I bought it with 110k from a doctor, who knows if he changed suspension parts regularly (I doubt).

 

If you bought it with 110k, you may also want to look at tranny fluid and PS fluid changes -- both expensive systems whose life can be prolonged by good fluid maintenance.

Mine feels nothing like a cruiser/tank though .. it's very sporty with a crisp, taught suspension. (I have the sport though). What brand/model struts and shocks did you put on the car?

 

All the fluids were changed as soon as I bought the car, including the steering wheel fluid, brakes fluid, oil, greases, etc.
Next week I'm changing oil to 0w/40 Mobil-1 fullsynthetic.
Mine is Classic, shocks are Bilstein (don't know exact model - I think basic ones, with black axle) and struts are new too, don't know which brand/model, probably Bilstein too.
The car rides slightly high but that's why it's so comfortable. Count in lazy automatic transmission, heavy diesel engine with lots of torque and you'll understand why it behaves like a tank/cruiser

EDIT: Does your car produce squelching sound when going over speed bumps? It's like the sound of walking in wet shoes... I don't know if that's shocks working or something else failing

 

For PS fluid did you use the MB spec CHF 11S? These systems will get ruined if you put in anything else.

I have the Bilstein TC (black) as well. I guess it's in the springs and sway bar then, since the rest of the suspension should be the same. Unless your diesel engine is a lot heavier ...

Squeeking over speed bumps when the suspension going up and down, is usually the front sway bar bushings. When I replaced mine the noise went away.

 

Honestly, I don't know what fluid did they put in...
It's not the squeeking sound, it's the sound of walking in soaking wet shoes, or dropping a wet towel on the floor, etc. I hope you understand. Is that squelching ?

 

If it's am MB dealer that did the service, then I wouldn't worry about it. But if it's an Indy I suggest you go back and ask them exactly what they put in. There are only a few fluidsthat are approved for the power steering systems in our cars ... if it's not Pentosin or Febi CHF 11S (it has to be CHF 11S) or the Mercedes fluid then you might want to report back what it is and potentially go back to the mechanic to have the correct fluid put in. Incorrect fluid in these cars messes with the rubber seals in the pump and rack, leading to steering shudder and possible leaking, leading to rack and/or pump replacement ... $2-3k. It takes months for the symptoms to develop, and once they do, either the damage is done, or it will take months to nurse the system back to health. I know, I went through it, and the jury's still out on whether the system was damaged or not.

Yeah, sorry, more of a creaking sound ... yes like wet or cheap shoes. That should be the sway bar bushings. These are easy to replace.

 

He said it's MB 345.0 certified oil for steering pump.
What that means, I don't know.
When I asked him what does it mean, he said it's certification that Mercedes gives to any oil manufacturer to produce oil by Merc's specific characteristics...now I hope that's OK, after all they've been a well known Mercedes service for a number of years, I don't think they'd gamble with something like that, otherwise they'd now have a bunch of cars with broken steerings...

 

Yes, that's the one for our cars, so you're good. Mercedes has different spec numbers for each fluid. Engine oil (and diesels are different from gas engines), transmission, PS, brake and differential. All very specific to model generations and engine types.

I don't doubt the expertise of the lead mechanics to know all the nuances -- it's the newly hired assistant mechanic who is not trained/certified that I might worry about making a mistake.

 

Phew... you shortened my life for a bit there

 

Fyi, here is a site that lists all of the MB specs:

http://bevo.mercedes-benz.com/bevoli...ets-sort1.html

You might also be interested in:

* 229.51 diesel engine oil (gas engines use 229.5)
* 235.7 differential gear oil
* 236.14 automatic transmission fluid (replacement for 236.10)

 

Thanks man, I'll check it out.

 

So...
2 days ago we changed inner tie rods (we thought they had some play) and stabilizer coupling rods because their bushings were damaged, but still the noise remains

Old:


New:


I'm beginning to think that the problem is somewhere around front springs. Could they have play?
Also, when I'm maneuvering slowly in reverse and turning my wheel to the left, I can hear knocking in the front left part of the car. As if something knocks down there while stretching/bending. Don't know what part could do that ?

EDIT:
Could you please explain this in more detail to me, since I suspect the problem is around this area...what do I have to do with struts and spring retainers?

 

delete...sorry