BLKROKT

Congrats for being right on that. You were wrong about practically everything else you posted.


Oh no you didn’t follow the instructions whatever will you do

Jasonoff

Sounds like the path of fluid flow may always go through the abs module block. Unless it's a return type system and it "filled up" the block while the car was running essentially bleeding air out of the module into the MC. Did you have to top up the MC at all after the gravity bleed?

I had a soft pedal when I first did a pressure bleed on this car years back. Slowly pumping the brake pedal while bleeding made a huge difference.

LOL, you do a couple track days and minor maintenance on your car and you think you're an AMG certified master mechanic now or something?

ItalianJoe1

Yes, the fluid always goes through the ABS block. From the master to the ABS/ESP module, then splits to the 4 corners. It acts as the proportioning valve in that sense also.

The ABS module has 16 valves that open and close to direct fluid where and when it's needed, along with a pump to create it's own pressure as needed. It can send or release pressure to any corner at any time, regardless of pedal actions.

In it's basic, unpowered, idle state, it's essentially pass-through. The pressure side valves are closed, and the release valves are closed, but the blocking valves are open. So on a new module, you could have air pockets behind some of the valves. Regular bleeding would work, but at the first ABS activation you could introduce more air into the main circuit. There is definitely a procedure during the initial startup that cycles valves and gets all the air out to prevent this. If you don't have a scanner, a couple good hard full-ABS stops, then re-bleed it, should do the trick.

Jasonoff

Thanks for the info! So a regular bleed would only miss a very small amount of old fluid.

Any idea of the affects a higher viscosity fluid has on the system? I know a lot of people have mentioned using RBF 600, SRF etc.

ItalianJoe1

I'm a dealer tech and we flush the cars every 20k, I've never noticed a change, even on cars that haven't been well serviced, in pedal feel. Me personally, I just run good OEM fluid but I don't track my cars so boiling points aren't really an issue. MB OEM fluid is a very good DOT4 fluid. I'd go to braided lines before I swapped fluids if pedal firmness is the goal.

Jasonoff

I mean the ESP/ABS system functionality in regards to fluid viscosity.

Vladds

So:
No ABS module
Our vehicle does not have SBC




The ESP module does have two functions that could be something.
One is the one that I was referring to yesterday.
The other is in case youโ€™ve replaced the unit.

Vladds

This is the procedure, the one that you attached, I was looking at in it the WIS. There's no mention about cycling the ABS in it.

Jasonoff

The pressure valves Joe mentioned which would bleed themselves activating ABS a few times on the street.

Vladds

Maybe upon seeing the screen with the left rear pressure valve, Joe will confirm that this is the one he is talking about, If this is the case, then what's the sequence with it? open the bleeder then engage the procedure to actuate the valve? all while stepping on the pedal?

And as part of bedding the pads in I did not only slow downs but also ABS stops, but I did not rebleed

Jasonoff

I would assume so. But it's probably a waste of time unless you replaced the ABS block.

Alex.currie44

I hear you but I change BF per the service manual which always seems to firm up the pedal feel. I have been doing it on 11 cars going back to my first W124 in 1987.

ItalianJoe1

ESP is the ABS unit. Same thing.

Vladds

Joe, help me out, because thereโ€™s nothing on the procedure.
So I have two controls
High pressure return pump and discharge valve.
I think the abs works based on a pump that build really high pressure. This is then released in order to counter the actuation of a wheel brake momentarily.
So possibly the cycle is that the emergency braking happens, the release valve releases counter pressure suspending the braking at the wheel that slips, then the high pressure pump rebuilds the high pressure in the high pressure accumulator.
So what would the bleeding be?
One actuation of the release valve, then one actuation of the high pressure pump then one actuation of the release valve ?
Then a bleeding session?
I mean actuating the release valve with the bleeder open may put a hole through the fender, no?
May be a really dangerous idea, right?
Who knows what kind of pressure weโ€™re talking about .....2000 PSI?

Jasonoff

The new ESP/ABS module replaced SBC right? Newer technology to essentially do something similar.

ItalianJoe1

SBC was an attempt at a different system entirely, it was used in the 211/230, but at the same time there were plenty of non-SBC cars using regular ABS/ESP systems.

ESP is simply Electronic Stability Program, which incorporates ABS along with a pile of other functions, all used to keep the car pointing where you want it to go.

SBC (Servotronic Brake Control) was a system that did away with the conventional, driver generated hydraulic pressure, instead using sensors and servos to calculate the drivers desired braking power and a pump to generate pressure and apply the brakes as needed. Good idea in theory, but overcomplicated things unnecessarily and when it failed, the resulting lack of braking power was quite dangerous. That's why that system never stuck.

ItalianJoe1

I wouldn't actuate the pump with the bleeders open, no. I don't have it in front of me, but there has to be a way to go into a bleeding procedure via SDS. The release valve is internal, it does as you suspect and lets pressure (either from the driver or pump) out to get the locked up wheels moving again. The pump is just that, a pressure supply independent of the driver, also used to apply brakes for stability/traction control functions when the driver isn't pressing the brakes at all.

Vladds

It's the reason I decided not to buy an E55. And was hated universally by the magazines at the time it was introduced. Clarkson was especially funny talking about it. I think that SBC also calculated and put out force feedback in the pedal, to give you the impression that you're still hydraulic. The problem was that each time you try to modulate, you get it wrong, or slightly wrong.
I guess the feedback from customers was so bad, that they decided to make it go away.
Then in the E55 forums, the owners are worried about the cost for the replacement of the SBC unit. it seems they all fail at similar high mileage.

However, as a foot note, the new Giulia Quadrifoglio also comes with a brake-by-wire system and there has not been one review that I've read so far that criticizes its brakes.

Which to me means that there is a "second generation" SBC system that is going to be introduced sooner or later.

BTW the first attempts with funky brakes were by Citroen which wanted a central hydraulic system, for suspension, brakes, steering and so on. Those also did not modulate well..