While driving yesterday (2005 E500) I suddenly got a brake warning, bright red "STOP" 'Reduced braking power Depress brake fully' and the brake pedal goes to the floor with little or no stopping action, very scary. Luckily I was only going 20 mph and was able to stop. After turning the car off and then on again I had full braking power restored and no red lights or warnings. I immediately thought the SBC unit has failed and had to get the vehicle to the dealer ASAP because there is an extended the warranty on the unit.

After spending 2 hours at the dealer the tech report came in stating, it is not the SBC unit and the hydraulics tested fine, instead the problem is with the BOU (Brake operating unit or master cylinder) and the cost to repair is little over $2,200.00. The car is well maintained brake fluid changed every two years, SBC software and wire harness upgraded.

I have searched this forum and other MB forums and every solution to this problem has been to replace the SBC unit, I have never heard of sudden master cylinder failure and after the car is stopped and restarted it's working fine again.

Anyone ever experience this or can share some thoughts on this?

 

Take it to a different dealer ASAP!!!!!!!!!!

A bad master cylinder will NOT be an intermittent issue. If it's bad, the pedal will always go to the floor. The fact that the issue went away after a re-start would be a good indicator that it's electrical.

I'd bet $10,000 the dealer would charge you for the master cylinder and then bill M.B for a SBC pump under warranty. Sounds like a typical "scum bag" dealership to me.

Go somewhere else!!!!!!!

 

My sentiments exactly, I have an appointment at another dealership tomorrow AM.

 

How many miles on your E ??

Mine has 100k, and I just had the SBC brake system software upgraded. (they say the sbc has the 10yr warranty, but they want to do the software upgrade first, which is not part of the warranty, so they get you on that, and if that doesn't fix anything, they then replace the sbc.)

 

111k, the car has been great up until now. The software and wire harness were upgraded under warranty back in 2007.

 

Ok good to know..

 

damn, these have been happening more recently

 

Took the car in to another Dealer for a second opinion today, after sitting with the SA I realized that it was a huge mistake, he ran my VIN and had the other dealer's report in front of him. They came up with the same diagnosis.

Error code "C261E" 'Hydraulic fault or brake light switch faulty'

The service director at the first dealership called me and with his concern gave me a number to MB corporate customer service and said I should express my concerns with them, I did and just received a follow up call from MB stating their position. They said -
"The vehicle is out of warranty and the component that has failed (BOU Master Cylinder) is not covered under the extended warranty provided to the SBC The repair is the owner's responsibility and MB will not provide any assistance in this matter".

With that said, I tried explaining to the rep that I don't have a problem having my car repaired, I know it's out off warranty, but there seems to be a major safety issue with the entire brake system on the vehicle and it seems as in my case according MB diagnostic results the electronics on the BOU (Master Cylinder) can fail suddenly, without warning, same as the SBC and it's not covered. The rep then repeated MB's position and the conversation was over.

It happens fast folks, as in my case you are driving comfortably as you get ready to stop and depress the brake pedal there is nothing there, no resistance, the pedal goes to the floor, then the bright red "STOP ME IF YOU CAN" light comes on and you pray that you stop safely without killing someone.

And it's like windows restart the car and it's fine again. mmmm

Be careful with these models as they age.

 

OK,
How about purchasing a new Brake Light Switch (since it states it "might" be that on their report) which MSRP is $10.50 at the dealer and replace that ******* yourself and see what happens.

That would be my next move considering the brake light switch is a common failure on the W211. Give it a shot!!!!!

 

Without opening a can of worms or denying what actually happens during the SBC failure, but in the September/October Star magazine there is a article on braking systems. One paragraph regarding the SBC that I did find interesting said "What happens if the electronics fail? If a fault should occur in the electronics, a hydraulic link between the brake pedal and front wheels is automatically restored, and the system will still stop the vehicle using the front brakes only. The brake pedal will travel down much lower and a host of red warning messages will light up the instrument cluster like the Rockefeller Center at Christmas"
Again, without this happening to me or my wife (I hope it never does), I do not know if the above information is accurate, but I would assume that there has to be some fail safe mode in the SBC system.
Just my $.02!
Mime T.

 

i think the problem was that the backup system never works properly

to the O/P, this really sucks. i mean i think MB needs to realize this isn't like the glycol contamination or something not that serious, this is a MAJOR PROBLEM in the actual braking system of the car!!! Very scary and imagine we are knowledgable to know that this might and we try our best to prepare for the worst... imagine those people driving these 03-06 E's, or 06's CLS, or SL's that DON'T KNOW about the chances of the system failing and what to do that's what scares me

 

I agree that MB needs to step up with this brake business.

I was headed from SoCal to Las Vegas the other week, and I went to the dealer for the "SBC 10yr Warranty" and instead got hosed for $240 for the AUX battery, which did indeed needed to be replaced. As far as the SBC? They wanted to charge me another $150 or so to flash the software, not replace the unit... I made a big stink about it and they threw the software upgrade in "for free" since they got $240 for the battery.... I hope my master cylinder or something does not cause death or catastrophic failure....

 

MB did step up when it extended the warranty to 10 yrs don't expect more unless people begin filing complaints with the NTSB so this data can be gathered.

I replaced my aux for about $80 myself. Battery available at Autozone.

 

Wanted to come back and give an update to this post, it's been a little over four months and 6000 miles since the SBC failure and the system has performed flawlessly since, no errors and stops great. The issue was escalated all the way up to MB corporate and I met with the MB area rep. They were sympathetic but offered no real assistance.

I did not replace the BOU (brake operating unit) only did a complete brake fluid flush, did it myself this time, it was previously done by the dealer at the recommended two year intervals, I have the receipts but it makes you wonder!! Also got hold of a star diagnostic tool and cleared the error code, Will also be flushing fluid at one year intervals if I keep the car.

 

guys i have the normal malfunction icon with visit workshop about the sbc, and ive been told my cars warranty is out of date and what ever happens im gonna be taking the charge for it as what do you guys suggest about this problem as stated any time the car will show the red screen the car has 187,000 km and has been to recalls about sbc before in 2007 but now the warranty is out of date the car is e320 2003 W211, any suggestions on what to do or say to the dealer?

 

How much to repair? might be the first thing you ask.

 

it would cost me about $3000 plus labour

 

Find a good independent shop in your area. Also maybe buy a sbc unit used off a parts car?
Probably cut your cost by 1/3.

 

if the SBC is at fault, replace it with a brand new unit...if you can. i wouldnt go for a used one coz it might fail again after a few months. just my 2 cents. goodluck mate! hope you fix your problem with minimal cost.

 

found a guy that said you dont need to change it he said i will just reprogram it and it will go fine and no need for the change and spending nearly 2k< it only costs he says $350 plus a guarantee it will work fine, rather im thinking of selling the car but at the same time the driving of this thing is nice and comfy, advice?

 

You need to question this fellow some more and find out exactly what he is claiming. What does he use to program it? How can he afford to make such claims etc.


Thanks for offering to check it out for us

 

I think this is the tool they use. They are for sale on ebay.
http://www.ebay.com/itm/new-Mercedes-Benz-W211-R230-ABS-SBC-Tool-clear-CODE-C249F-/321317313417?hash=item4ad0011b89&item=321317313417&pt=Motors_Automotive_Tools&vxp=mtrI think it just turns the dash warning off by resetting the counter. I am not endorsing this in any way. I have just seen them on ebay while looking at available software.

 

he told me the SBC needs reprogramming as it has a technical and mechanical systems he said most of them have the technical problems as technically can be reprogrammed but when it comes to the mechanical wise it needs to be changed to a new one.

as the one on mine is mechanically down and needs to be changed but he will reprogram the SBC unit so it can work on its status for about 2 to 3 years max with a guarantee but after that no guarantee, if mechanically it was good the guarantee is another 10 years.

so that was what information i got from him.

 

I had total SBC failure and was also able to stop. The car was put on flat bed sent to dealer for repairs. My issue is I never / ever had any vehicle have total brake failure using conventional vac. booster system stop. The SBC adds complexity and isn't IMO as reliable as the vac. system. I will not drive a car with electric brakes again. I sold my MB and bought a Chrysler 300C 5.7 hemi and haven't looked back. Nice driving with more power 29.mpg highway (measured) 365+ hp and knowing the brakes work.

 

just put mine on for sale, i wouldn't of sold it if it wasn't from the SBC unit, seriously Benz isn't looking at its customers anymore its just looking for money now.