I would never rely on my transmission to slow the car down! The brakes are peanuts in comparison.

 

Actually you already do it each time you slow down. The automatic lowers gears as you slow, not just to be in the right gear in case you choose to accelerate, but to use engine compression to help slow the car.

The automatic does it conservatively for the sake of comfort. Doing it by hand with the paddles allows you to downshift sooner than the auto would making it less comfortable and more jerky, not necessarily harmful to the transmission.

Have you ever noticed that the MB cruise control downshifts quite abruptly if you are going downhill and start to exceed the set speed?

I don't know, but I suspect the transmission wouldn't let you "paddle-down" to a gear that would be destructive to itself.

Regards,
Don

 

I hate how the CC does it so abruptly, though I understand that it's to hold the set speed at any cost.

I usually let the CC go if I know it's going to downshift hard or brake hard to match speed, then re-engage when it gets to the new appropriate speed.

 

There were NO obvious deposits on the rotors. I do not race my E550. Also, this is a luxury configuration and not the sport. All E550 have drilled front rotors. The brake pads were just fine (they don't give off much dust either, BTW).

Runout can be caused by poor metallurgy. That would lead to high and low spots. The fact that some people have reported pulsating brakes at very low mileage is more an indication of poor finishing by the vendor rather than improper use of the brakes.

 

did you get to keep the rotors at least??

 

Yes agree, there is some kind of defect. Seems to be I hear more of these issues with the 550 as opposed to the E350 w/sport rotors that are perforated. That's the only reason I thought heat and cooling design could be an issue only on that model. I'd be curious if there is now a new part number for the rotors if MB says the issue is solved moving forward.

 

I had mine done 2000 miles ago and wondering if the replacement is a permanent fix or I will be back to see the dealer at 20k? Have any of you with earlier failures had the problem reoccur?

 

I did not ask for the defective parts.

 

I use the paddle shifters often when descending a steep long grade. The transmission is designed to provide engine braking. I have never had transmission issues doing this in any vehicle I have owned. I do not subscribe to this being dangerous or harmful. It is necessary function that works as intended for driving in mountainous conditions. These cars really do not need to be babied.

 

I agree 100% with using the transmission to slow you down prior to braking. I grew up in the trucking business prior to joining the USAF. As a result, everything I originally learned about driving, I learned from professional truckers, including my Dad.

Today, I still drive the way I was taught in the early 60's, regardless if I'm drving an automatic or a manual transmission. Most of my cars have been manuals, simply because I like changing gears. The Vette still has the original ceramic pads I installed the weekafter I bought the car. It now has over 40,000 miles, and visual inspection shows no noticeable pad wear at all, because I use the transmission to slow the vehicle first.

I was involved in a similar thread on the Silverado forum two years ago. Some guys were saying, using the automatic to slow the truck was hard on the transmission. I use my automatic to slow my Silverado all the time. I am usuallly driving somewhat spiritedly and it helps on break wear and fade.

I used the paddle shifters to slow my wife's Ml350 when she had it and I now use the paddle shifters to slow the E350. I have always done it and will always do it, I have never had any transmission issues and have never changed break pads on any new vehicle I have ever owned. I have owned 65 vehciles and 36 of those have been new.

We did change the pads on the ML350 at about 35,000 miles beause my wife drives like Parnelli Jones and uses nothing but the brakes. (She got a speeding ticket coming home from work one afternoon, clocked at 92 mph.) She drove it 95% of the time. That was too heavy of a vehicle to drive like she did, concerning brake wear.

 

Yikes,now I'm concerned.Like you most of my miles (80+%) are Interstate miles so brakes are the last thing I'd think of at 10K...20K..maybe even 50K miles.What *is* "runout" any way.Never heard of it.What are the symptoms of "runout"?

 

Yikes,in my youth I was a bit like your wife (but not 92mph) until I began my 20 year stint working in a large hospital's ER.Since then I haven't gotten a single ticket for a moving violation (now that I've seen what can happen).

 

High and low spots on the rotors, measured with a micrometer, even small amounts will cause pulsating.

 

oj, time to get your wifey a w212 or a vette instead .

 

And let's not forget, pulsating is a braking efficiency issue and, therefore, a safety issue.

 

Yes, absolutely, especially in rainy/slippery conditions, I would imagine, ABS early activation as well.

 

There is definitely a problem with the E550 brakes but Mercedes so far will not admit it. My rotors were warped at 9000 miles. The dealership replaced them free of charge, however the problem reoccurred at 20,000. This time the deal ship told me that I must be riding the brakes, doing panic stops or a lot of mountain driving and refused to fix the problem. I am a very conservative driver and none of this occurred. Further more this is my third e series and I never had an issue before. I called Mercedes and while they were nice they called the dealership and then backed them up. When I told them that there had been many problems reported, they said they only go by their engineering department and not blogs. The dealership also said that both front wheels were bent and that may be a contributing factor but would not consider that the brakes overheating might have caused this as well once again accusing me of being an abusive driver. The new e550 is a very nice car but Mercedes needs to own up to this problem.

 

This is the most common reason for deposits on the rotors; but doesn't sound like you are one of those who abuse them. There is a cooling issue with these brakes on the 550. Modern rotors are made of iron and don't warp, the runout is caused by layers of pad deposits, causing raised areas that pulse the brakes. Seems the pads/rotors or both are not dissipating heat adequately. Many times, after a lot of stop and go, we sit at a light for a long time, with those pads pressed against the hot rotor, which can cause the deposits to form, but this generally only happens at break-in time. Keep us informed of your outcome.

 

I, too, am a VERY conservative driver. NEVER ride the brakes --- my left foot has never left the floor since I had a stick shift in the 70s! I NEVER have panic stops, and had done some mountain driving, during which on long grades I dropped down a gear to take the load off the brakes. In other words, I absolutely do not abuse brakes --- but I don't abuse transmissions, either.

In my case of severe "pulsing" at 9100 miles with even moderate braking, the dealership did what the book tells them to do --- they measured runout on all the rotors -- .005" in front, .004" in rear. (The pads were at 10mm.) The dealer replaced all four rotors and all sets of pads. They then put 10 miles on the car testing and seating the brakes.

(They DID imply, however, that had I reached 10,000 miles, they would not had covered the repair. After some discussion, they modified that to 12,000 miles.)

I am now at 18,500 miles and things are great. Let's hope I don't have your experience at 20,000 miles!!! I have another 3,000 mile trip planned next week, which includes mountain west driving. If I end up with pulsing after that, and MB refuses warranty service, then the car goes to an independant shop for measurement, and then my attorney and MB will have a little talk. Frankly, this car has been an absolute disaster as far as reliability is concerned --- brakes, Airmatic, transmission, rear seats, IPOD connection failure.

The trick for the THEORY about the problem being deposits, not warping, is to measure the runout just outside the area where the pads lie. If you see it there, the problem is the rotor warping, not some deposit supposedly .005" thick laid down by the pads.

 

Had my rotors changed due to pulsating (34k miles). They didn't cover it. They did cover a leak (rear differential) under warranty at the same time. I brought up this thread and related reports, but with my mileage and SD modded height, i didnt push too hard since they're still honoring my warranty. $600 and change for pads/rotors/labor at my dealer fyi.

My commute is 40 mins to an hour (each way) of stop and go traffic. (L.A.)

 

The pulsating brakes have been the only real problem with my E550. Started at about 8k miles - I went to the dealer with about 15k but they would not replace under warranty. Now I have 31k miles and the pulsating upon stopping is awful. For such an expensive car they should take care of something like this under warranty.

 

I agree! I've had this problem on my GL since 20k and he dealer fails to acknowledge that there even is a pulsing. They claim it's the ABS. however all they're giving me is BS. I told them to check the rotors and they said they were fine...

 

transmissions get damaged by heat. Downshifting often to slow the car down cause heat buildup. The Energy gets transferred somewhere... in this case it is channeled through the transmission in the form of heat. It breaks down the fluid and will cause damage.

 

In my opinion, pulsing brakes are brakes that aren't working correctly. A huge safety issue. I'll bet your panic braking is only a fraction as effective as a set of good brakes.

If I were MB, I'd be really worried about huge lawsuits for injury in cars with pulsing brakes in an accident caused by insufficient braking.

 

Don't always believe that your wheels are warpped as you could have the tires out of round creating the illusion of wrapped wheels. I had this situation occurred to me with the factory Continentals all-seasons.