SL/R230: Brake issues




As soon as I started the car I got abs light with reduced power to the car any thought
You say you did "a complete brake job." What all did that entail? Pads? Rotors? Brake bleed?
Did you disable SBC before you began your work?
What was the problem and how did you get it resolved?
I am going to replace pads and rotors on my R230 in the next coupla weeks. I'm trying to learn from others.




Yes I did do a complete brake job. All new rotors (Zimmerman) Akebono pads and I replaced all the hardware clips and retaining pins. I tried to disable the SBC unit but wasn't sure how to after I did the brakes got red light ABS warning and car went into limp mode car. Called my Indy made an appointment to have him put it on the SDS but the next day tried the car again and everything was back to normal? Still had him put it on the SDS and the code said SBC unit had a glitch and reset itself. And while it was there he did a brake flush. Maybe someone can explain how to disable the SBC unit so we can all benefit
Some people w/o SDS will just unplug the electrical connector from the SBC unit, but that does not relieve pressure, it just keep the pump from running. You need pressure relieved so that you can safely work on the brakes without damaging them or yourself.
Last edited by Rudeney; Jun 22, 2017 at 10:20 AM.
Question: after deactivating SBC but before starting the rotor replacement work, should the brake reservoir be uncapped and should a quantity of fluid be removed from the reservoir? (And replaced after the work is completed, of course).




http://benzbits.com/r230/DeactivateSBC.pdf
Like I said, don't try to unplug it - that does not release pressure on the system, it only keeps it from re-pressurizing.
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Are those two separate and necessary actions? Or does deactivating SBC discharge pressures?
I know how to deactivate SBC using SDS, but "discharging pressures" ... I don't know about that.
You know the humming sounds you hear when you open a door, or step on the brake before starting the engine? That's the SBC pump operating to pressurize the system. It also does this periodically as you drive, but you won't hear it with the engine (and radio) running. That's the "finite" lifespan part of SBC that can only happen 300,000 times before the pump must be replaced. It's not 300,000 brakings - it's 300,000 pump runs. One pump run can provide dozens of brakings, depending on conditions.
The SBC system is actually more than just an electric pump in place of a pneumatic booster. It can measure the pressure on each brake caliper so that it knows the position of the pads relative to the rotors. It can apply the brakes for you without you pressing the pedal. of course this happens with the ESP/BAS system, but it also does this when the wipers are on (to dry the brakes) and will even move the pads close to the rotors the moment you lift your foot from the accelerator - closer when you lift your foot off very quickly as if you are about to slam on the brakes.
Here's some interesting reading. This is for the MY2009 refinement, but it mostly applies to all SBC-equipped cars (I think the brake hold features was not added until MY2009, and it's not available int he USA anyhow):
http://benzbits.com/r230/SBC_Functions.pdf
I plan on replacing all my car's rotors and pads within the next week or so. I will disable the system with SDS before starting work. Your posts have informed me greatly about my car's brake system and the perils of working on it, and I thank you.
PS. While using SDS several months ago, I changed my "car nationality" to something other than USA ... maybe Germany or Switzerland. Doing so enabled me to activate the flashing brake light feature. I think it also enabled the hill-hold feature ... earlier my car did not have hill-hold, but it has since changing nationality. Go figger.
Last edited by Heatwave; Jun 23, 2017 at 03:11 PM. Reason: Additional info




Anyhow ... I followed your advice regarding deactivating and later reactivating SBC via SDS. Everything worked perfectly. Many many thanks for that sound advice. The hardest part about the SBC/SDS work was dragging out the ancient Dell laptop, the multiplexer, the wires and cables, the power cord, and getting it all set up, then unplugging everything and packing it properly in the storage case.
Deactivating SBC was a piece of cake: select an option on the SDS screen and it's done. Reactivating was illuminating ... listening to the SBC system cycle through its steps in restoring balanced pressure to the brake lines, and seeing the four-brake results on the laptop screen gave me a great appreciation of the importance of deactivating/reactivating the brake system via SDS.
I replaced only the rear rotors/pads yesterday. The front brakes will have to wait a few weeks ... it takes more time now for my old body to recuperate from an afternoon of lying on my back and trying to generate enough torque on a wrench to turn damn tight brake bolts. I sure wish I had a garage lift.
Thank you for your insistence on deactivating/reactivating MB brakes via SDS. I'm a true believer now.
As for the beach, we did have some weather from TS Cindy. We got to Destin on Monday and it was overcast. Tuesday and Wednesday were very rainy and windy, but that's OK as I had some maintenance things to do around the condo - my niece's husband installed a new cable box and now the programmable remote doesn't work it, so I had to fiddle with that. Plus a curtain rod broke. We don't actually go to the "beach" - my wife will not get in the ocean and we really don't care much for sand. We just like being there to relax, hang out at the pool (me mostly - she's decided she does not need the sun), and eat some fresh seafood. Thursday ended up better - at least no rain, but Friday was beautiful. We were coming home Saturday, but stayed until today (Sunday) since it was so nice.




Please keep in mind that while this will disable the pump motor and keep SBC from cycling or operating the brakes, it DOES NOT relieve any pressure already in the system. You should not rely on this as a substitute to properly disabling SBC when servicing! Also, after replacing brake components, it is necessary to have the SBC system recalibrate itself, which only happens if it was properly disabled.
Last edited by Rudeney; Jul 4, 2017 at 11:12 AM. Reason: fixed image link




(As a side note, my LR brake disc is running hot, since all discs, shoes and parking brake shoes were replaced, so we're looking for a reason, perhaps the parking brake needs simple adjustment).



