anybody have sbc actually fail on them? What happens? Do you lose your breaks? Can you stop without rolling to a stop?

 

 

When the pump fails to build pressure, the brake pedal must be pushed all the way and hard to where the emergency hydraulic circuit will take over and give you very limited braking power to the front wheels only. Can't say I'd care for that to happen when I need to stop RIGHT NOW but it'll be enough to stop the car so you can change your underwear.
Look around the site; there's a very detailed explanation from Mercedes on this very topic.

 

This only happens when you don't service the SBC system right? It's not something that should not happen if the system has not been neglected?

 

Not necessarily. Some folks are of the mind that there's a timer of sorts on the system that will cause the red warning after a certain number of braking cycles/switch activations. Certainly there are documented cases of the accumulator (pressure tank) failing and needing to be replaced. Sometimes an electric motor (the motivating force of the hydraulic pump that is the heart of the SBC brake system) simply fails. Like all complicated pieces of machinery, there are plenty of modes of failure. Fortunately, at least here in the USA, Mercedes has extended the warranty on the brake system for 25 years. There's a sticky thread at the top of this forum that you might find interesting.

 

Search the old threads. It can and does happen. It's basically considered a ticking time bomb. The pump is mechanical and MB keeps track of how many times the brake pedal is pressed and has a warning come on when it reaches a certain threshold. Like anything mechanical though, it has a average mean time between failure so while it's a conservative estimate, a certain percentage will fail before that count is reached. Back when it wasn't covered, some people would just get a reset device that resets the counter. So now you wouldn't even get a warning if it was reset, the pump would just fail. And because it's an extended warranty and not a recall, MB won't replace the pump until you hit that threshold. Basically they say you lose 90% of your braking power when it fails which is why you need to change you underwear. Some claim it feels like 0%. You really need to plant your foot when it fails. Strangely enough there aren't really that many reports of crashes/deaths from the pump failure so it's not really that common but probably one reason why MB extended the warranty to 25 years instead of the 10 that it was originally. I guess that would have been bad press from people who didn't want to pay 2k-3k+ to get it repaired at a dealership. It's one reason why I stayed away from pre-2006 models as you would never know if the brakes might fail on you unless the pump was just replaced.

 

That's quite frightening to think about, but I've only seen one video of it actually failing while someone was driving .

 

You don't lose 90% of braking power. That's BS. If you want to see what happens just disconnect the plug as shown in the video. I have, it's really not that scary. The only difference is that you press the brake pedal all the way down. Don't pus5y foot.

 

Read the old threads. That's what gets mentioned many times. Only reporting what others have said.

 

Good to hear. It seems that if you were to lose 90% of braking power that these cars would all be recalled and not road legal.

 

Having felt what 100% of braking power is on these cars, I know personally these two things:
1) the SBC brake system is, hands down, THE best brake setup I've ever experienced on a car. Stand on the pedal and you better have your eyelids closed because your eyeballs just might pop out otherwise. Mine almost did.
2) Even only 10% of that is a LOT of braking power.
In other words, I'm not terribly worried about electromechanical failure and I'll deal with it when it happens.

Drive happy.

 

You would think that, but when you have a master cylinder failure, it's also kind of the same thing. almost no braking power. Basically just depends on when it happens. At least a master cylinder isn't a 2-3k repair at a dealer.

 

Last I checked my SBC still has another 9 years on the unlimited mileage warranty.

 

I don't think you got the point I was trying to make. A master cylinder on some other car can be in the $50 range and labor is normal so you're out the door for a couple hundred dollars. If you're worried about your master cylinder dying on you, it's not that expensive to replace it in advance. On the other hand with SBC, they were failing in under 10 years so many people got it fixed under warranty and those that were over 10 years had to pay 2-3k at the dealer before they extended the warranty to 25 years after a few years. The other problem is that you have to go to the dealer to diagnose that it's an SBC pump failure which would be covered under the extended warranty, if it's something else like the ABS pump which can also fail and give you similar warning messages, then you have to pay for that out of pocket as it's not covered. And a master cylinder failure will leave you with minimal brakes just like an SBC failure, but it's allowed which was the point I was trying to make. SBC is considered to be better brakes than regular brakes, just like people love the airmatic suspension. But only when it's working right.

 

Im not sure where you're coming up with this. SBC is the ABS pump. There is no separate ABS pump on these cars. The extended 25 year warranty covers everything SBC related including work done prior to the warranty being extended. MB refunds those repairs even if they weren't done at a dealer. Thr replacement SBC units have much longer life expectancy than the originals. There's no reason for preventatively trying to replace it. It's now over engineered and extremely reliable.

It's easy enough to pull codes from the SBC unit. The warranty codes are clearly defined. It even covers the wheel speed sensors.


For anyone still curious about how the brakes work after an SBC failure, find a large empty road or parking lot, pop it in neutral with the engine running, put on the parking brake and unplug the SBC as shown in the video. Now drive it. You won't be able to go very fast but you will be able to stop the car without a problem. Turn off the engine, plug it back in and SBC is back to normal. It ain't rocket science.

 

This was my post when our 2003 E320 hit the SBC limit and was fully covered by MB in Nov 2019.

https://mbworld.org/forums/e-class-w...2003-e320.html

 

Yes you do. Not BS. That video with full engine compression controlling speed in first gear is a ridiculous portrayal of 90% brake failure in a real driving situation. Wife lost SBC at 65MPH on a busy six lane freeway before the holidays, and was very lucky to avoid hitting anybody (and to avoid being hit).

Had the brake/ESC warning 4-5 days earlier, but it followed a low battery warning on a very cold morning after not being driven for over a week, and turning the car off and on again cleared it. Car drove normally for those next 4-5 days, and the warnings didn’t come back until the moment of failure.

Serviced annually by the same dealer since new, roughly 115k miles on the car.

IF YOU SUSPECT AN SBC ISSUE, BRING IT IN AND EXERCISE THE EXTENDED WARRANTY.

 

My 2003 E320 (since retired) experienced SBC failure on the down ramp of an overpass. There were no previous warnings whatsoever. It took 1000 feet to bring the car to a stop from 45 MPH. I kept the car until 2016 and 186,000 miles, but I was glad to see SBC replaced.

 

You know your car has an emergency brake. Its that 3rd pedal on the left.

There's no such thing as "90% brake failure". That's a bull shlt excuse from a **** driver. You still have full use of your front brakes. And just like every other car on the road, SBC still requires a brake fluid change every 2 years. When was the last time you had your brake fluid changed? I'll wait while you go dig up the receipt.

 

Silly me! I’m glad you checked my maintenance records. Vulgarity just increases the effectiveness of your replies.

 

Is that right?
While I'm not going to take the time to dig into the posts I've read on this forum that are documents published by the Mother Ship, I'm going to say the words I've turned red are not only wrong but dangerously so. While you are correct in that the front brakes are the only ones working in the emergency circuit of the SBC system (all the way towards the bottom of the brake pedal travel is where the non - computerized hydraulic brakes kick in), you have nowhere near the full use of said front brakes.
I'll wait while you go dig up documents supporting your statement.

 

My 03 e320 is making some groaning gurgling noises from the pump area. I can push my brake pedal almost to the floor in park. But I have no warning light . Just had pads and rotors too. They better replace this pump and not try and tell me, well since the emergency SBC light isnt on it's not covered under warranty

 

No warning lights, just did the brakes and rotors. Did you bleed the brakes? Probably have air in the lines. You could also scan for error codes. You may have pending codes that don't trigger any lights. If they scan and don't find any codes, then they probably won't cover anything so don't clear any codes if you find them.

 

Thanks, yeah I didn't and wont erase any codes. The noise was there before I did the brake job. That's the reason I did the brake job. I thought maybe it was the rotors or something weird because it almost felt like they were pulsating or not grabbing right. The groaning is getting worse by the day. Sometimes after I just start the car and not even touching the brakes. But mostly after i release them from a stop and creep forward. You can definitely hear it from the front passenger side of the engine. Its definitely an electronic groan. I wonder why the SBC light doesn't come on. I mean you can almost push the pedal to the floor board.

 

My best guess is air in the SBC unit. You cannot clear this if you are bleeding by just using the pedal or using a suction at the brake nipple. It requires the following:

1. Positive pressure brake bleed system. You must have at least 2 Bar or 29PSI at a minimum to open the valves in the SBC. Without this pressure the internal valves will not open even if using the Star SBC brake bleed (or other high end scan tool).
2. Requires slow pumping of brakes to clear any air from the master cylinder with the 29+ PSI

It is a two part process. First with the 29+PSI positive pressure, you do a normal 4 wheel brake bleed - including slowly pumping the brakes. Then you go through the SBC flush via the star which will again have you flush each wheel. This is the only way to clear all the air once air gets into the system.

Here is what I use for positive pressure brake bleed. I use around 32-34 PSI for our MB's. I use this on all of our cars - not just the MB's. Other cars need different adapter, but this one comes with the one for MB's. I have attached the WIS instructions for the brake bleed. Basically I pump it up to about 34 PSI and start bleeding, slowly pumping brakes, and stop and re-pressurize it when it gets close to 30 PSI. I can do it solo but its easier with someone to assist.


Side note. Both our W211 and W210 are past due for brake flushes and both will get this soon. I will be switching to Bosch ESI6 brake fluid on both of these cars. One of the lowest price I have found is Rock Auto for the Bosch ESI6 but prices lately from everyone have gone up.