You can’t bleed SBC brake without a MB Star Diagnostic C4

Finally, I believe to bleed the SBC brake with a MB Star Diagnostic C4 is the safest & working way.

The story goes back to when I was a beginner: My 2005 E320 CDI needed to bleed the brakes, and I managed to bleed the read brakes without the Star Diagnostics.

According to what I read the ABS pump motor is activated each time the door is opened. When the door is opened there is a faint buzzing sound that comes for the ABS unit. This is to ensure that the system is pressurized before the car moves. After I got the front brakes bleed and reactivated, I crawled under the car at the pass side rear wheel and i had dad open the door. Once i heard the pup running I opened the bleeder screw. When this happens the system senses that there is a loss in pressure and tries to pump up the system. If you hold it open long enough the SBC system detects that there is a problem and shots off on its own. You also get the SBC red light in the dash. Once the bleeder screw is closed and the key is inserted in the ignition everything went back to normal. I had to repeat this several times but i managed to bleed the read brakes without the Star Diagnostics. Once both sides were done i deleted the codes and no problems since then. There were other things we had to replace such as fuses, the fuseable link from the starter to the alternator, the fuse that is under the driver side kick panel (from amazon for couple of dollars).”

Post my experience to Benz forum and hope this will help someone in the future.

However, they don’t agree my experience completely. Here post some points.

There is no master cylinder as you know it on SBC brakes.The buzz you heard was the hydraulic pump pressurizing the accumulator (the bulb on the side of the SBC pump).

You may be bleeding pressure out the bleeders on the brakes, but you’re not hitting (at all) the hydraulic circuits that are the backup safety system for the car. To do that, you need to (wait for it) use the MB STAR diagnostic system that can turn the solenoids on and off.

There’s a lot of good info on how the system actually works, but you have to search a bit for it. Here’s a diagram to get you started.

Bleeding the Brakes without Star will not get a 100% flush, here reference link: https://mbworld.org/forums/w211-amg/373572-diy-brake-fluid-change.html

Tip: This is not your grandfather’s hydraulic brake system. It is a brake-by-wire system, is extremely complex, and improper procedures can result in damage and/or bodily injury.

Just buy a STAR system and do the proper procedure.

if interested please see here:

https://www.chinaobd2.com/wholesale/mb-sd-connect-compact-4-star-diagnosis.html

So, how to bleed the SBC brake with a Star Diagnostic?

Take w211 for example:

Go to the SBC control unit screen and select General Servicing.

Then Replace Brake Fluid/bleed brake system

Next screen reminds you of the bleed sequence…

At this screen make sure your bleed hose is connected and sitting in your container so when you hit F3 you can go crack the bleeder open while the SBC builds pressure. You’ll hear some valves open and close and then a burst of fluid go into the drain container. After that it slows to a steady flow and the STAR screen will basically tell you what to do next.

Here’s a sample screen after I finished with the left rear caliper and moved on to the front calipers. Each of the front calipers have two bleeders – one on the outside and one on the inside. Outside one’s are bled first.

Almost done…moving on to last bleeder.

There will be a couple other screens after this which are self-explanatory. After those I removed the pressure bleeder and made sure the proper amount of brake fluid was in there and closed the system. The last thing I did was run this pressure check where there SBC tests the system to make sure it’s holding the correct amount. 90bar was factory spec if I recall and mine was 88bar so I’m good to go.

Install the plastic cover over the reservoir, shut off the ignition, start the car, check for any codes, and you’re done.

Done!