LILBENZ230

Hey guys, I have one of these intermittent issues with my C230 that has developed in the past week. I'm at 70,000 miles and this happened right after new tires were mounted. Both nights I have noticed this it has been raining out, I'm not sure that this has any bearing on it but I wanted to mention it. Tonight it was dry and the problem vanished. Here's a description of the issue:

When rolling backwards in reverse, the car would emit a constant metallic scraping noise from the rear. It sounds a lot like a brake pad audible warning, which would make perfect sense. The car has 70,000 on the original rear pads and no rear pad wear sensors. Fine, simple enough, I thought. But if it were a pad wear audible warning, it should do it consistently. In every previous car of mine, once the audible warning starts it will do it every time. The silence tonight from my car is much more disturbing because now I just don't know.

Ideas? Thanks!

Carsy

Simple, remove rear wheels & check brake pad thickness.
If the pads are down to the metal they won't be doing your disc rotors any favours.
I do not feel comfortable unless I know the approx thickness of my brake pads.
Keeping a log of them is a good idea ( Thickness Vs Kms ) & you will be able to forecast the rate of wear .

e1000

There's no audible warning clip on any MB pads. You'll hit metal to metal if you don't have the wear sensors in place. You can check the thickness of the pads with a flashlight without taking the wheel off if you can find the right angle.

Glyn M Ruck

Do you have one of those strange cars with 1 pad wear sensor up front?

I think you are out of back pads.

The only other things likely after rear wheels off are:

Wheel not tightened
Hoist damage to an exhaust heat shield through carelessness
Tyre shop lost a lug bolt & replaced with a longer one that is fouling the park brake mechanism (common)

e1000

This one's got my vote too.

FYI, I think all US spec w203's 2005 and up only have 1 wear sensor on the front pads and 1 in the rear, both on the passenger side.

glocati

Good call on your last point Glyn. Matt mentioned he just had tires installed, so that is definitely something to check that most would not even think of....

LILBENZ230

My car has just one sensor on the front. There's not a sensor on either side on the rear. I'm gonna check this out today. I assumed that with the lack of a sensor on the back, Benz would have made sure that you weren't suddenly metal on metal with no warning.

Glyn M Ruck

e - around the world these cars vary from 4 brake wear sensors like mine to 1 like Matts. Wierd - I know. Cost cutting at Benz.

e1000

Yeah I know, I just always thought in 2005 they had one on the front passenger and one on the rear passenger. I know that's how mine is. I've actually seen a chart somewhere that has all the models and years and where the senors are. Can't seem to remember where I saw it though.