TomFree

I am the veteran of a lot of different cars, and a lot of different brake jobs, but my '04 C320 4M wagon seems to be doing something I've never experienced before - I'm getting what seems to be brake pad deposits on the rear rotors from sitting still! The car is stored outside and driven rarely - maybe once or twice during a week, and 2-3 times on a weekend. 95% of the time, the car is parked without the parking brake set.

When I bought the car in April, it had a little bit of vibration under braking, but after driving it for a few days, it went away. The vibration I have now is a LOT worse, and doesn't seem to go away after a couple of days of driving.

How do I know that it's the rears? Well...I just replaced the front rotors and pads this weekend, and the car still exhibits the same behavior. I bedded in the new fronts (Akebono Euro Ceramics) using the StopTech procedure (10 stops, cool down, 10 stops, cool down). After the bed-in, the vibration/noise is less, but definitely still there. The car only has 47K miles, so I'm almost certain that the pads and rotors on the rear are original. I have new rear rotors and Akebono Euro Ceramics on the way.

So...I feel confident that replacing the rear pads and rotors will take care of my vibration issue, but is there something about this braking system that is unique? Is this issue going to come back? Are the rear pads rusting to the rotors, even though the parking brake isn't set? Is it an issue with the original pad compound?

LILBENZ230

Even with the parking brake set the rear pads shouldn't be touching the rear rotors.

TomFree

Ah, I haven't done the rear brakes on this car yet. Parking brake is a drum that uses the inside of the rotor, I take it.

Great, that makes it even more confusing. I've checked the rears after driving, and I don't notice any unusual heat, i.e. no sticking rear calipers.

Glyn M Ruck

Carefully rotate all the wheels & look for a pad shaped mark on any of the rotors. If such marks are visible they can cause vibration. If the Stoptech bed-in procedure does not clear them you will have to mechanically clean the rotors by sanding or giving them a light cut on a rotor grinder.

Of course the other problem might be a warped rotor - check rotor run-out. Never run cold water on a hot rotor when washing etc. Even running through deep water with hot rotors can distort them.

Ceramic pads are sometimes a poor choice for cars that stand. Ceramic based friction material by it's very nature can be somewhat porous & hold moisture which can lead to rotor spot corrosion. The dusty OE pads take this into consideration.

Good luck!