SBC: How difficult to stop car once it goes out? - Page 5 - PeachParts Mercedes-Benz Forum

mannys9130 · #61 11-22-2015, 10:24 PM

Quote:

Originally Posted by Mark DiSilvestro

Awhile back, I decided to not own any vehicles with ABS. While ABS often malfunctions by simply shutting down, leaving the brakes to function normally without ABS, sometimes it can malfunction by reducing braking power if the computer 'thinks' it's needed, even when there's no slipping or skidding condition present. A friend has a '95 Camry with ABS that activates every time the car slows to about 3-4 mph. It feels like it's suddenly sliding on gravel. Very unnerving!
Other friends have occasionally had the ABS on their vehicles activate needlessly at much higher speeds, without warning. Then the system resumes functioning normally when the vehicle gets to the repair-shop.
As I buy used vehicles long past warranty, I have no desire to gamble on aged or neglected electronic safety technology. I'm adding SBC to my 'to avoid' list.

Happy Motoring, Mark

Tell your friends to unplug the ABS unit...

Deplore · #62 11-22-2015, 10:29 PM

lol @ the amount of misinformation here.

I have replaced the SBC in two different cars, and I can tell you the car gives you a warning LONG before the SBC fails.

There's the white messages with two different messages, and then there's the red message with SBC failure.

If you get to the point where the SBC fails, you've been basically ignoring the previous message. It shows up EVERYTIME you start the car. You'd have to be blind and deaf to not notice the beeping and the cluster message.

FWIW, the SBC actuation limit varies wildly, but usually it's about 600,000 actuation. The white message shows up around 350,000 to 450,000. The second white message shows up at 500,000 and up all the way to 600,000 -- and then SBC deactivates itself with a red message.

Yes, a failed SBC means reduced braking power -- the braking force is marginally more powerful than the handbrake, but it will stop the car.... eventually. But then you must've been ignoring all that message up to that point.

SBC is a wonderful piece of equipment and I will not hesitate to buy a car if it has one equipped. So long you're well informed and equipped to understand how SBC work, you'll be fine.

It's like knowing when to replace the engine oil, transmission oil, differential, etc. SBC is just another component that you add to it. That's it.

All this hysteria is totally overblown, imo.

barry12345 · #63 11-22-2015, 10:33 PM

Quote:

Originally Posted by dude99

Seriously? So instead of just a service soon warning it shuts itself off?!?! if this is true I would replace it as a maintenance item upon buying a car with SBC and just chalk it up to a cost of ownership\necessary safety.

Maybe any dealer can tell you how many pushes of the pedal are left.

Actually this post coincides with something I earlier thought I read, It just was not clear.

There is still enough confusion to talk to a good Mercedes dealer. It may be a simple case of resetting the counting device before the unit hits its pre programmed limit. If it is allowed to do so it may not be resettable.

There has to be something there as even Mercedes could not allow the system on the road for potential liability issues unless they had an escape.

I again as it was so cloudy got the impression when they changed the fluid and bled the brakes as a maintenance item they reset the counter.

You do not maintain the car to their specifications you lose your brakes? They may have lost any liability. At the same time I would find this very strange engineering.

It also is odd that the posters message above my post was not general knowledge. I just went back and read it. Pure and simple it is designed to stop functioning. Maybe the onset warnings have been missed for those that have experienced sudden failure. If this is the case they are pretty safe systems as long as you watch for the indicators after all. I wonder how many people have decided to sell these cars when a Mercedes dealer tells them you are starting to approach unit replacement time. Nothing much surprises me anymore.

dude99 · #64 11-22-2015, 10:45 PM

Quote:

and then SBC deactivates itself with a red message.

Whats the rationale for it deactivating itself?

Deplore · #65 11-22-2015, 11:18 PM

Quote:

Originally Posted by barry12345

Maybe any dealer can tell you how many pushes of the pedal are left.

Actually this post coincides with something I earlier thought I read, It just was not clear.

There is still enough confusion to talk to a good Mercedes dealer. It may be a simple case of resetting the counting device before the unit hits its pre programmed limit. If it is allowed to do so it may not be resettable.

There has to be something there as even Mercedes could not allow the system on the road for potential liability issues unless they had an escape.

I again as it was so cloudy got the impression when they changed the fluid and bled the brakes as a maintenance item they reset the counter.

You do not maintain the car to their specifications you lose your brakes? They may have lost any liability. At the same time I would find this very strange engineering.

It also is odd that the posters message above my post was not general knowledge. I just went back and read it. Pure and simple it is designed to stop functioning. Maybe the onset warnings have been missed for those that have experienced sudden failure. If this is the case they are pretty safe systems as long as you watch for the indicators after all. I wonder how many people have decided to sell these cars when a Mercedes dealer tells them you are starting to approach unit replacement time. Nothing much surprises me anymore.

MB dealer can actually tell you the number of actuation -- you can poll the number of actuations in the SDS.

MB used to replace the SBC when the messages showed up -- though lately they've issued a new TSB (I use the word "lately" very loosely, as they released that years ago) that basically said read the number of actuation, reset it, and then program a new software that extends the number of actuations before critical failure.

(note, the below paragraph is speculation and from my and other conjectures and is not hard fact)

The new software apparently (again using that word very loosely) changes how SBC functions which in theory would extend the practical lifespan of the pump. It also introduces new monitoring procedures that if the requirements are met, it immediately deactivates the unit. MB (obviously) has kept mum about the specifics, but our conjectures is that it monitors how much force it takes to move the piston in the MC and the amount of pressure in the master cylinder and elsewhere. If the pressure does not meet/exceeds a certain tolerance (indicative of piston wearing out or crud in the brake fluid sealing the hydraulic fluid circulation), it immediately deactivates the unit.

Keep in mind that the SBC master cylinder pressure is measured in bars, and polling the MC pressure sensor in SDS returns a number between 100-300 bar. So it's conceivable that the brake line pressure exceeds that number.

FYI: 100 bar = 1500 PSI. Water based CNC cutter use a water pressure of 1500+ PSI to cut metal.... so imagine 1500 PSI of hydraulic fluid exploding out of a brake fluid line or the master cylinder erupting under pressure---it leads to all sort of liability for MB...especially if the hot hydraulic fluid hits the exhaust manifold or the exhaust tubes.... fire, fire everywhere.

(end speculation)

hangit · #66 11-23-2015, 07:24 AM

My brakes have been flushed by a MB dealer every two years as recommended since new. I asked them to interrogate the SBC for number of activations and was told they could not do it.

Go to this site and file a complaint. Home | Safercar -- National Highway Traffic Safety Administration (NHTSA)
Several owners state the system quit abruptly with no prior warning messages. Did they service their brakes as recommended? No way for us to know.

John

shertex · #67 11-23-2015, 08:00 AM

If, as Deplore suggests, I will get white warning messages, I am fine with being the proud owner of an SBC system. If there's a chance the first warning I get is red warning (and the loss of braking power that goes with it)...that's what makes me nervous.

MTUpower · #68 11-23-2015, 08:39 AM

Quote:

Originally Posted by Deplore

lol @ the amount of misinformation here.

I have replaced the SBC in two different cars, and I can tell you the car gives you a warning LONG before the SBC fails.

There's the white messages with two different messages, and then there's the red message with SBC failure.

If you get to the point where the SBC fails, you've been basically ignoring the previous message. It shows up EVERYTIME you start the car. You'd have to be blind and deaf to not notice the beeping and the cluster message.

FWIW, the SBC actuation limit varies wildly, but usually it's about 600,000 actuation. The white message shows up around 350,000 to 450,000. The second white message shows up at 500,000 and up all the way to 600,000 -- and then SBC deactivates itself with a red message.

Yes, a failed SBC means reduced braking power -- the braking force is marginally more powerful than the handbrake, but it will stop the car.... eventually. But then you must've been ignoring all that message up to that point.

SBC is a wonderful piece of equipment and I will not hesitate to buy a car if it has one equipped. So long you're well informed and equipped to understand how SBC work, you'll be fine.

It's like knowing when to replace the engine oil, transmission oil, differential, etc. SBC is just another component that you add to it. That's it.

All this hysteria is totally overblown, imo.

Your personal experience does not jibe with others personal experience- and remember it's just that- your own personal experience. You - by your post- have not experienced SBC failure. You've experienced replacing SBC prior to failure.
Do you have a link or some other type of proof about the braking power of a failed SBC to back up your conjecture?

leathermang · #69 11-23-2015, 09:32 AM

Quote:

Originally Posted by shertex

..... If there's a chance the first warning I get is red warning (and the loss of braking power that goes with it)...that's what makes me nervous.

That is what I would worry about also...

Mark DiSilvestro · #70 11-23-2015, 10:34 AM

If the engineers can design diesels to go into limp-mode or shut down if the Ad-Blue fluid is depleted (something that is NOT a safety issue), they should have done something similar with the SBC. This sounds like a potentially serious safety issue!

Happy Motoring, Mark

spark3542 · #71 11-23-2015, 10:39 AM

Quote:

Originally Posted by Deplore

lol @ the amount of misinformation here.

I have replaced the SBC in two different cars, and I can tell you the car gives you a warning LONG before the SBC fails.

There's the white messages with two different messages, and then there's the red message with SBC failure.

If you get to the point where the SBC fails, you've been basically ignoring the previous message. It shows up EVERYTIME you start the car. You'd have to be blind and deaf to not notice the beeping and the cluster message.

FWIW, the SBC actuation limit varies wildly, but usually it's about 600,000 actuation. The white message shows up around 350,000 to 450,000. The second white message shows up at 500,000 and up all the way to 600,000 -- and then SBC deactivates itself with a red message.

Yes, a failed SBC means reduced braking power -- the braking force is marginally more powerful than the handbrake, but it will stop the car.... eventually. But then you must've been ignoring all that message up to that point.

SBC is a wonderful piece of equipment and I will not hesitate to buy a car if it has one equipped. So long you're well informed and equipped to understand how SBC work, you'll be fine.

It's like knowing when to replace the engine oil, transmission oil, differential, etc. SBC is just another component that you add to it. That's it.

All this hysteria is totally overblown, imo.

As I said in my previous FIRST-HAND response...There were no white warning messages at all in the previous 250k miles. Just the red message and limited braking ability.

Even experiencing the brake failure, I love my CDI, and will buy another in a heartbeat.

Mark DiSilvestro · #72 11-23-2015, 10:48 AM

Quote:

Originally Posted by mannys9130

Tell your friends to unplug the ABS unit...

What I am capable of doing with my car, and what my friends would be capable of, or comfortable with, doing to theirs, are two different things.
But God forbid I should have an accident, and some insurance investigator discovers my ABS has been deliberately disabled.
That's one reason why I won't own a used vehicle with ABS.

Happy Motoring, Mark

Skid Row Joe · #73 11-23-2015, 12:20 PM

Quote:

Originally Posted by Mark DiSilvestro

What I am capable of doing with my car, and what my friends would be capable of, or comfortable with, doing to theirs, are two different things.
But God forbid I should have an accident, and some insurance investigator discovers my ABS has been deliberately disabled.
That's why I won't own a used vehicle with ABS.

Happy Motoring, Mark

It seems far fetched that unplugging an ABS unit would ever culminate to the point you have suggested it might here, but of course forensic investigations of placing liability for a mishap could take place.

I would advise your friend(s) to consider trading out of these vehicles with malfunctioning ABS units. Sometime you just have to let old equipment go and replace it.

Skid Row Joe · #74 11-23-2015, 01:39 PM

Quote:

Originally Posted by hangit

My brakes have been flushed by a MB dealer every two years as recommended since new. I asked them to interrogate the SBC for number of activations and was told they could not do it.

Go to this site and file a complaint. Home | Safercar -- National Highway Traffic Safety Administration (NHTSA)
Several owners state the system quit abruptly with no prior warning messages. Did they service their brakes as recommended? No way for us to know.

John

Could not, or, would not? I know you wrote "could not do it," but my next question would have been; why?

Quote:

Originally Posted by shertex

If, as Deplore suggests, I will get white warning messages, I am fine with being the proud owner of an SBC system. If there's a chance the first warning I get is red warning (and the loss of braking power that goes with it)...that's what makes me nervous.

I'm with you here. I think we need to spend some time with our respective MB dealer's service advisors to try and find the accurate answers on this one. There's conflicting information here on thread - then there's a lot of information being alleged as fact too. Enough so, to go beyond this thread to the MB dealers to try to ascertain the actual facts regards these systems, from their actual source.

shertex · #75 11-23-2015, 03:08 PM

Spoke to service adviser at dealer. He said most of the time you get the white message first. But not ALL of the time.