SL/R230 Need Help – SBC Brake Issue, Dealership Won’t Cover or Source Brake Operating Unit (M

Jul 31, 2025 | 12:06 AM

zedw205

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2019 w205 c300 Sedan

Need Help – SBC Brake Issue, Dealership Won’t Cover or Source Brake Operating Unit (M

Hey everyone,

I’m hoping to get some help, advice, or tips from folks who’ve dealt with SBC brake issues before.

I recently had my SBC hydraulic pump fail on my 2005 SL500, and thankfully the dealership replaced it under the 25-year extended warranty. However, they diagnosed the brake operating unit (BOU)—also referred to as the brake master cylinder—as bad as well.

Here’s the issue:

They claim the BOU isn’t covered under the warranty (which seems questionable).
The OEM part is discontinued from Mercedes.
They told me to just go source a used or aftermarket part and get it handled at an independent shop.

This is my project car. I’ve already done the coilovers, alternator, and fixed the roof, so I’m comfortable tackling this myself.

I sourced a used OEM brake master cylinder and am planning to install it, but I need help understanding the bleeding process—specifically with the SBC system. I have an iCarsoft MB V3, but I can’t find any clear option for SBC deactivation or bleeding in the menus.

Has anyone:

Done the SBC bleed themselves with an iCarsoft MB V3 (or know how to access it)?
Used a different tool that works reliably for this?
Installed and bled a replacement master cylinder on the SL500 with SBC?

Any guidance, steps, tool recs, or general advice would be hugely appreciated.

Thanks in advance!