My wife drives a 2007 E320 Bluetec that we bought certified preowned from a dealership up in Roanoke, Virginia (we now live in Texas) with 8,500 miles back in April 2009. We're now at 39,100 miles and a couple weeks ago she mentioned a grinding noise coming from the back rear brakes. She took the car in on Friday and the dealership shared that the front brake pads were 85% worn and the rears were both metal on metal with scored rotors. They shared that 39K on rear brake pads was actually pretty good. This surprised me. And they were ready to charge me $520 to have new rotors and pads installed on the rear axle.

I'm mechanically inclined and currently the not thrilled owner of two homes so I thought I would have a look and see if it is time for me to do the job myself or at least have an independent shop do the repair.

Well, this afternoon I went ahead and pulled the wheels to see what was up. First surprise was that neither wheel had been pulled at the dealership shop as the corrosion took quite a bit of banging before either tire would break loose.

The second surprise was the there is a brake pad sensor on the passenger side inside pad and it was still in tact (and the reason why no warning had come up with my wife during the past 32K miles). I also noticed that the caliber must have seized as the outside pad was metal on metal even as the inside pad (with sensor) is still roughly 4 mm thick.

The third surprise was that the driver side rear pads had plenty of life left even as the outside of the rotor was somewhat scored.

Question to all of you is whether I have grounds for a warranty service. It seems to me that the caliper failed and the sensor failed in its mission. And the dealership certainly didn't thrill me with the effort they put into their inspection.

Thanks in advance for your advice. It will help me when I'm on the phone with MBA USA tomorrow!

Regards,
Trevor

 

The car went back into the dealer service center today and this time they did pull the wheels and had a better look. And they stuck to their explanation that 4 mm of remaining pad one on side of the rotor and metal to metal on the outside pad does not reflect any malfunction. According to them, the caliber wasn't seized. They shared over the phone (I work 65 miles away during the week) that they had a M series on the rack right next to it that had a similar situation going on.

Left scratching my head I called MB North America and spoke with Bobby on the customer service line. He put me on hold and spoke with others. He came back and shared that my car has traction control and if the driver has a heavy foot (which my wife doesn't) that the traction control applies the brakes to stop the spin and this could cause the outside pad to wear faster than the inside pair. Has anyone heard of this before? I'm mystified. Does this make sense to anyone?

Again, how can a brake pad sensor on one side of the rotor not be triggered while the other side is metal on metal? Mercedes is known for their safety. Why would this be an acceptable design?

Won't someone talk me off the ledge with an explanation?

Thanks for caring.

Regards,
Trevor

 

The reason the brake pad sensor did not trigger is that is not the way it is designed. It will trigger only when the sensor makes electrical contact and completes the circuit. Sensor is not on the pad that is causing the problem. If it was working correctly both pads would be wearing about the same. Sounds to me like you have a stuck caliper piston that is not releasing and wearing the pad. Have you had the brake fluid flushed on the car. It is routine maintenance required every two years. If that has been done then I would continue to challenge the dealer because the explaination your are getting does not make sense.

 

The word is caliper, by the way.

Caliber is a measurement.

 

English is a funny language. Caliper can be a brake caliper and also a measuring tool.
Caliber refers to diameter of the inside of a round cylinder, such as a tube or bore of a firearm. It is also a degree of worth as in a person of high caliber.

 

LOL. I need to be more careful with my typos. I used the right word twice and the wrong one twice. And every time I get an alert that there has been a new posting on my thread I get hopeful that someone is going to provide some feedback that confirms or refutes my concerns about the diagnosis, only to find comments on my poor diction. :-(

Does anyone else have an opinion on my brake C-A-L-I-P-E-R challenge?

Thanks,
Trevor

 

39K on a set of rear brakes is perfectly normal for everyday driving. Brakes are a wear and tear item to dealers. They have seen issues like this many more times than you have. If they say it's a normal condition; go with it. At least it is on record with the dealer and the issue was brought to their attention.

If you know for a fact that the caliper is an issue, you can pay for it to be rebuilt. Just because you think it is a problem, it doesn't mean the dealer has to replace it under warranty. If they get into it and find a defect, then they may help you out, like splitting the cost or covering it under goodwill.

Talk to the service manager, ask for the shop foreman to look at it and he will work with you.

.

 

I did speak with the dealership's Service Manager and he was the first person to agree that having one pad out of four on the rear axle wear down metal to metal while the others have plenty of life and the front pads having 15% life and no pad wear sensors fire wasn't normal behavior for a car with only 40K miles.

Although his techs shared they could not find anything to explain the wear he did comp the fix and is processing it as a warranty repair.

Way too much drama getting to a good outcome, but a good outcome nonetheless. My lesson learned is finding the right person to engage.

Happy motoring. And thanks for the assistance.

-Trevor

 

Glad to hear it worked out for you.