Strange "kvack kvack" noise - solved

[Herlax]

Many professionals tried to diagnose the strange speed dependent noise coming from somewhere from the front or middle of the car. Including Mercedes authorized service with specific request to find out and remove the "kvack kvack kvack" -noise, typically between 20-70 kmh. It was a sporadic noise, not always present. It took about 3 months to finally solve it. By accident.

I had the front brake disks and pads changed. After removing the right side disk it could be seen that the brake dust shield was loose. Could not be seen without removing the disk. Now the car is finally silent again.

I wanted to share this, perhaps obvious discovery to many, so that no one else is forced to drive with "kvack kvack" car without checking the brake dust shields.

 

[ray_hennig]

Many professionals tried to diagnose the strange speed dependent noise coming from somewhere from the front or middle of the car. Including Mercedes authorized service with specific request to find out and remove the "kvack kvack kvack" -noise, typically between 20-70 kmh. It was a sporadic noise, not always present. It took about 3 months to finally solve it. By accident.

I had the front brake disks and pads changed. After removing the right side disk it could be seen that the brake dust shield was loose. Could not be seen without removing the disk. Now the car is finally silent again.

I wanted to share this, perhaps obvious discovery to many, so that no one else is forced to drive with "kvack kvack" car without checking the brake dust shields.

Good to know.

I had a 250CE back in the 70s and a rather limited budget. One day I was aware of a dreadful "bag of nails" sound from the back. Immediately though that the diff was about to disintegrate. Doom, despondency.

I looked underneath and could see no problem. I just happened to ease the brake dust shield aside and a small piece of gravel dropped out. Problem solved.

RayH

 

[Herlax]

Many professionals tried to diagnose the strange speed dependent noise coming from somewhere from the front or middle of the car. Including Mercedes authorized service with specific request to find out and remove the "kvack kvack kvack" -noise, typically between 20-70 kmh. It was a sporadic noise, not always present. It took about 3 months to finally solve it. By accident.

I had the front brake disks and pads changed. After removing the right side disk it could be seen that the brake dust shield was loose. Could not be seen without removing the disk. Now the car is finally silent again.

I wanted to share this, perhaps obvious discovery to many, so that no one else is forced to drive with "kvack kvack" car without checking the brake dust shields.

F.Y.I. My vehicle is W211 220CdiA Sedan, 2008, 160.000 miles. The dust shield fasteners were ruined by corrosion. Like 2 different quality metals tend to react. Very strange.

At least these potential sources for the noise were checked and ruled out before the reason was finally discovered:
- gravel in the brakes
- broken alloy rim
- all bearings and supporting structures
- rim fastening bolts: if penetrating through the rim a bolt may touch material on the back side of the rim.
- "hand brake" (parking foot brake) joint at the brake end. Known to cause "kvack kvack" if not anymore as it should be.

I feel a bit frustrated that it was I who finally determined, not professional authorized MB service engineers, to open the brakes with a slightly "premature" front brake reneval to seek for possible "kvack" source.