What ACTUALLY Happens When SBC Fails?
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From: In the Shadow of the Tetons
2013 ML350 Bluetec
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.
Look around the site; there's a very detailed explanation from Mercedes on this very topic.
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E55 AMG
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.
Look around the site; there's a very detailed explanation from Mercedes on this very topic.
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From: In the Shadow of the Tetons
2013 ML350 Bluetec
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.
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From: MA
2008 E350 4Matic, 2011 E350 4matic
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.
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E55 AMG
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.
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C320
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.
Last edited by tjts1; Jul 5, 2020 at 04:48 PM.
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From: MA
2008 E350 4Matic, 2011 E350 4matic
Read the old threads. That's what gets mentioned many times. Only reporting what others have said.
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E55 AMG
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.
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From: In the Shadow of the Tetons
2013 ML350 Bluetec
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.
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.
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From: MA
2008 E350 4Matic, 2011 E350 4matic
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.
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C320
Last I checked my SBC still has another 9 years on the unlimited mileage warranty.
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2008 E350 4Matic, 2011 E350 4matic
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.
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C320
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.
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.
Last edited by tjts1; Jul 5, 2020 at 09:55 PM.
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From: SD
2000 C230 - 2001 E430 - 2003 E320 -
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
https://mbworld.org/forums/e-class-w...2003-e320.html
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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.
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2021 GLB250 FWD, 2023 GLA250 FWD, 2013 C250, 2015 GLK350, 2005 ML350SE, 2003 E320
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
IF YOU SUSPECT AN SBC ISSUE, BRING IT IN AND EXERCISE THE EXTENDED WARRANTY.
IF YOU SUSPECT AN SBC ISSUE, BRING IT IN AND EXERCISE THE EXTENDED WARRANTY.
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C320
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.
Last edited by tjts1; Jan 6, 2022 at 02:47 AM.
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2021 GLB250 FWD, 2023 GLA250 FWD, 2013 C250, 2015 GLK350, 2005 ML350SE, 2003 E320
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.
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.
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From: In the Shadow of the Tetons
2013 ML350 Bluetec
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.
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.
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.
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E320
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.
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From: MA
2008 E350 4Matic, 2011 E350 4matic
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
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E320
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.
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From: SD
2000 C230 - 2001 E430 - 2003 E320 -
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:
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.
- 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).
- Requires slow pumping of brakes to clear any air from the master cylinder with the 29+ PSI
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.
Last edited by tyabnet; Nov 27, 2022 at 11:57 PM.
