SBC Predictable Life Expectancy
 

Assuming one has an SDS system and knows how to use it, can the total SBC system actuations be determined?

If so, is there a "fails at" number of actuations programmed into the system? If so, what is that number, or does it vary according to such things as "hard actuations" vs. "soft actuations," or such?

My car is a full 10 years old, but only 47,000 miles. MB's 10-year SBC warranty expired at the end of April. I prefer to do a bit of preventive maintenance so as to avoid catastrophic system failures. But I don't want to service the SBC unit if it still has, predictably, several years of expected service remaining. "If it works, don't fix it."

It appears from posts on this forum (and others) that SBC works perfectly right up until it quits. I'd like a little more warning or advance notice than that.

What can you tell me?

From what I know, you can find the actuation count with an SDS. Have not tried to find it with mine, but I've seen it on posts.

MB set the SBC system to 'time out' before failure. That means if the average failure is 500K uses, they set it to 300K to ensure it is replaced prior to failure. There may also be a time variable added to the 'time out' determination.

Depending on if you feel lucky, the system could be done at 301K, 500K or 1,000K before failure. It's a bell curve for failure, and all cars will fit into that curve.

I also believe the most common SBC failure is the motor that drives the pump. The rest of the valves and electronics are pretty reliable, and have redundancy, so you are able to stop just fine. Member bayhas on the Benzworld forum knows this system well.

W211 SBC count check

Note: Engine does not need to be running to only obtain count. Engine must be running if you are going to reset the count.
Start Xentry, go through menus for your vehicle and go to:
Control units
Chassis
SBC sensotronic brake control
Development data
Actuations (should be at the bottom of the menu so scroll if necessary)
Complete index of Actuations

Select “Bremsenzaehler (DF_GetBrLiveTime)”. This returns the total count to date. Stop here if only getting the count and back out of the menu using the F1 key.

Having said the above, SBC was discontinued on the E-series from 06/2006 build date onwards. So...check your build date first. I can't answer for your SL.

WIS (Document SN00.00-P-1047J — Overview of innovations/changes 06/2006) reads:

Model 211/219
As of code 807 Model year 2007

Introduction of Adaptive Brake (ABR)

As of the model year, the previous SBC brake system is replaced by the further developed Adaptive Brake system. The comfort functions "Hold" and "Dry braking" from the current brake are retained. The ESP control unit and the traction system hydraulic unit are now a compact component.

In vehicles with ABR brake, the driver is made aware of ABS regulation by pulsation of the brake pedal.

The new brake system is bled without STAR Diagnosis. Further information can be found in the WIS.

once you reach 300,000 actuations it must be replaced. every time you hit the brake pedal or the stability/traction control is engaged counts as an actuation. you can no longer buy new sbc units, only rebuilt ones. the cheapest place i have found one is huskerparts.com. when it reaches the end of the service life (300,000 actuations) the car will tell you in the dash, first with a blue message and then with a red message (when the red message appears the car will disable the sbc completely and you will only be able to use the backup hydraulic system, which only applies the front brakes with no power assist).

FYI- all r230 SLs have the SBC system as mercedes did not believe it to be worth it to reengineer the braking system on a low production vehicle like the SL. They did figure out it was worth it to do it on the E class though.

also, there is no preventative maintenance that can be done, other than a brake fluid flush every 2 years (you need a STAR tool to do this procedure and each brake caliper has 2 bleeder valves). Once the counter reaches 300,000 the thing is done and they don't usually fail before the 300,000 count is reached.

So, if they don't usually fail early, the requirement to replace the unit is based on this hard limit of 300,000 actuations? So what would happen if you just reset it in SDS? Could you then just keep going until it truly fails?

You can, but it's not a great idea. Try unplugging the electrical connector that goes to sbc & see how well the backup system works. It's pretty scary.

Oh, I can imagine! I was just thinking that the MBZ engineers probably erred on the side of safety. Meaning that it probably goes 500K, so they chose 300K to force service.