E55Florida

Hi all,

Reading through this forum has been invaluable. After about a month of ownership, I am in love with my 2005 E55, except for one major thing: the brakes. I have scrolled through the SBC posts and realize that it is a feature which many do not like.

As a new owner, I have noticed very strange brake modulation. - Particularly, coming to a stop, the brake pedal pressure feels fine until the car comes to rest. As my foot holds the brake at the same position and fiddle with the radio etc. I will all of a sudden realize the car is creeping forward ever so slightly. It has almost resulted in a rear ender, and concerns me. I have tried to make it a habit to place slightly more pressure (to the point of not feeling natural) on the brake pedal after the car comes to a stop to prevent it from rolling into the car in front. The car has plenty of life in the rotos and pads. Does this sound like a typical SBC related quirk that I just need to get used to?

I dearly miss the "hold" feature in my previous M-B's. Even without the hold function, they did not have this problem of having to place more pressure on the pedal once the car came to a gentle stop. It is very strange and annoying.

Thanks for your input,

Eric

machild

Are you 100% sure there is no leak of brake fluid. The symptom you exlpain is very similar to a leak as the leak reduces the pressure in the braking system and requires further foot pressure to keep the car from rolling. A very careful examination of the entire braking system is required to find an external leak.

Another similar situation is where the master cylinder is leaking internally. In this case, the seals inside the master cylinder are letting pressure past them when pressure is created and that too requires increasing foot pressure to hold the car from rolling. But, in this case, you can not see a leak as it is just leaking from one side of the master cylinder piston to the other side. A pressure test is the only way I know of to 100% diagnose that kind of failure.

SICAMG

What Machild said....look for a leak or....the seals for the master that you fill with fluid is leaking past the seals internally wich is probably the issue.

JohnLane

“Brake master cylinder?”

Friend your 211 E-55 is equipped with SBC. When you apply the brakes via the left pedal you are making a request to OZ which decides how much pressure (via a hydraulic pump) to apply. There is said to be a ‘backup brake master’ built into the system ‘for emergency’ but I can tell you from personal experience that it isn’t worth a damn and sure isn’t going to save you. Has your SBC unit been replaced? If not it is long overdue. There was a warranty extension for it when I had my E-55. MB was kind enough to pay for a percentage of it.
Bleeding brakes in your car requires XENTRY. If you don’t have it get with Peter AKA BenzNinja and buy the computer and membership.

nd-photo.nl

Correct, the "master cylinder" provides your foot with fake brake feedback based on sensor(s) input. Its a brake by wire system which has it flaws and might be the only thing I don't like about my CLS55.

I got my SBC pump replaced not to long ago under warranty. All expenses paid, but you need to get it diagnosed by a certified MB dealer for them to go through with the procedure.

SICAMG

Nd - you snuck right in there before me !!LOL
Yes brake master cylinder. It consists of.Brake fluid reservoir,SBC pedal value sensor, Tandom master cylinder,brake pressure simulator and is sold as one unit called a BOU- Brake Operating Unit
Also you do not need Xentry to bleed brakes . A pressure canister filled with brake fluid will do the job. I have done it a few times with Xentry and always ended up just "pushing" the fluid out with the brake bleeder system. I am sure many have done it with the computer but my luck was always to use the bleeder system and it is much much faster.

nd-photo.nl

I believe the official procedure is to use STAR/Xentry, but I've read numerous times that it can also be done just with a pressure bleeder. If I am not mistaken, you need to be using 2.5 BAR to do it properly. Also, it takes DOT 4 PLUS and not the normal DOT 4.

SICAMG

Correct. And the pressure bleeder works well even with this system.

machild

Another part of the pressure only bleed setup is to disconnect the SBC unit located under the hood in the right front. And with that disconnected you do NOT want the car to wake up or remian awake while the SBC unit is unplugged. That includes not having the key anywhere near the car if it has push button start and do not open any door or trunk or anything else that will make the car's network to wake up. If it does wake up with the SBC unplugged, it will set fault codes for, at least, the SBC controller which requires code clearing before driving the car. I'm not sure, but the fault(s) that are set may need Star/DAS/Xentry to clear, hopefully not.

rnd_ash

This is interesting!

The SBC system itself does various self tests and will alert you if something is wrong. What milage does your car have? Personally I don't think anything is wrong with your car, but I'll explain below why.

Very early on when SBC was released, it had a feature called "SBC Soft-stop". Coming to a halt, the SBC unit will let go slightly if the brakes to avoid a jolt when coming to a stop. HOWEVER, this feature was disabled very quickly after the w211 released due to the number of complaints it has caused and near accidents.

It is quite possible that if your SBC unit has never been changed, it has that feature still enabled! It may be worth going to your dealer and seeing if they can check if it is enabled and if so, disable it. If you have Xentry itself, it can be found under adaptations / control unit codings on the ESP ECU (ESP actually talks to SBC over a separate CAN network to tell it what it can or can't do).

This all said, if your SBC unit has never been changed, do it ASAP! If you are in the USA, MB should do it under warranty.

Best regards

RAND_ASH

E55Florida

Thank you very much for the insight. That is interesting about the "near accident" complaints and sounds familiar to what I have noticed. It has about 49,000 miles. The prior owner has had the car since about 2013 and barely put on any mileage. - I don't have the repairs from the original owner. So it may very well have never had the SBC changed. I will let the service advisor about the warranty and request they change it. Hopefully they don't give be pushback.

E55Florida

Thank you for the info! The PPI from the MB dealership in Ohio didn't mention any issues, but a leak in the brake system could've easily been missed.

E55Florida

Thank you for the advice. The prior owner barely drove the car and has had it since around 2013-2015. He has told me only routine maintenance has been done in the few thousand miles he drove it. I have no idea if the original owner had the SBC replaced. - Hopefully the Dealer will honor the warranty if they see that it hasn't been replaced when the service advisor searches the maintenance history in their internal dealer service network - however that works.

E55Florida

Thank you! Is there anything you need to provide to the dealer for them to honor the warranty now that the car is 18+ years old? I am now the third owner, so any extended warranty notice about the SBC pump would have gone to the original or second owner I presume. (And I highly doubt it was ever completed)

E55Florida

I will request the dealership to replace/look into the items you mentioned. Thank you! The parts don't appear to be too expensive, so hopefully the bill will be reasonable. I would think mentioning the specific parts (brake fluid reservoir, SBC pedal value sensor, etc..) to the service advisor would help diagnose the problem(s), and forgo any beating around the bush by the dealer.

nd-photo.nl

I had error messages off course. I waited a couple of months before taking action (bad idea) and then it struck, in the middle of the highway (doing 60) the brakes failed and I had about 5% unassisted brake left. That was scary....Fortunately, there wasnt a lot of traffic and I could get it to stop safely.

After that incident I immediately stopped driving and made an appointment at the dealer. Error messages: https://mbworld.org/forums/c219/8443...ml#post8651162

SICAMG

I am waiting for this wonderful experience of brake failure to happen to me at some point and hopefully will be a long way down the road. My problem is I will NOT let the dealer or anyone else touch the car so will fix it myself. I worked in a dealer for 15 years and know what goes on so ......I will take care of it myself and spend the money, hate to do it but I'll sleep better for sure and WELL worth it ,for me at least.

rnd_ash

SBC is no joke (and also why it was only ever fitted to a few cars)....maintenance on these units is awful.

Be sure to REPLACE your unit if it goes bad. Do NOT just change the accumulator and reset the SBC module by some Chinese OBD adapter as I've seen so many do on YouTube. These units count up the wear and tear on their pressure motor over time, and just erasing EEPROM via these adaptors is one guaranteed way to have an unsafe car, as you are basically tricking the unit into thinking it's fresh by erasing it's history of brake applications, and thus wear and tear.

That said, if you go the proper way and replace your SBC unit when it goes bad, you'll need Xentry to properly bleed the hydraulic system afterwards, since there is no master cylinder in these units....pressing the brake pedal to "bleed" air out will never do anything for the rear calipers, since those are not physically connected to your pedal. Xentry has a specific routine for bleeding the entire hydraulic system and all the caliper lines

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SICAMG

Well aware and have done a few of them. There were also places that rebuild them in the US that I have used and worked well.

E55Florida

Wow! That must have been terrifying. I too tend to proscrastinate more than I should with these sorts of things. Thanks for the link and I appreciate the input.

E55Florida

I am skeptical of the stealership as well, unfortunately, without knowing how to do much more than an oil change, I have to take it in to someone. With my past experience at various indy shops in South Florida, I wouldn't trust taking the car there any more than the dealer. It is a catch-22, but I'll just hope they know what they are doing and bite the bullet.

nd-photo.nl

It was...Again, fortunately it happended while I was cruising. Totally different story when you are measuring 100-200kph times or doing cornering or something else