Tech question- Brakes
 

I looked into postin in the technical forums, but not much is going on over there, in the brakes section.
I had bled my brakes and I think I have slightly soft brakes.
I've read in the past that people had the ABS gear cycled using the Xentry and that took care of the problem.
Only I can't find a procedure to cycle the ABS in the WIS and I can't find an ABS cycling feature in the Xentry.
Was this a thing of the past?
What's up with the bleeding procedure in the Xentry where they say it's ok to leave the bleeder open and gently pump the brakes, to replace the brake fluid.\?
I've never heard of pumping on an open bleeder, what's the tech background of this? I mean I had a bleeder out and it's still a bleeder, not a one way ball valve.

The bleeding procedure assumes you're using a pressure supply or bottle on the bleeder, I assume. I haven't had to do it on a 204 yet so I don't know specifically what it says.

There's not really any reason to get air in the ABS module unless you replaced it. Why did you bleed your brakes in the first place?

I'm an old school guy. No reason, I replace brake pads, I bleed the calipers and then I bed the pads in. Get all you can get out of the brakes...
I mean, a reason?
You don't touch the bleeders, eventually there will be a problems as you have dissimilar materials in contact, steel bleeders into aluminum calipers. Steel threaded into aluminum. Gota move or else electrochemical corrosion will eventually get them seized.

I also replaced the brake fluid with fresh MB fluid. I am not experiencing any longer brake pedal travel, on the contrary a slight action on the pedal is now enough. It just feels softer to the touch than before.
I am reading now that this is normal for fresh MB brake fluid, as the old fluid becomes less viscous because of absorbing humidity.
Also, I was reading the records of the car, it was at the dealer for scheduled service by previous owner many times. But I could clearly see the calipers had not been touched.
At this point, according to the maintenance manual, it was supposed to have had 2 brake fluid changes already ...

This brake system is just not one that delvers a high hard pedal no matter what you do. I was tired of the same slightly soft pedal and did a patient gravity bleed, tapping each corner with a rubber mallet to get every last air bubble out. Dropped the car and tested the pedal out...it was still soft.

Not necessary. Our cars don’t have SBC. Also the Motive really shouldn’t be pressurized over 20psi for our cars as my understanding is that high pressure will actually damage the ABS seals. Those E-class instructions shouldn’t be followed, sorry.

WIS says 2BAR for bleeding.

I have a Motive power bleeder and never got that pedal feel I was looking for. Are you guys getting that high, hard pedal using it?

You're supposed to slowly pump the pedal while power bleeding. It helps quite a bit when you do.

I also believe the screens are the same for ABS/ESP or whatever as the SBC screens in the link I provided. There's a way to cycle abs pump while bleeding to flush it. It's the replace procedure.

So I was las night in the car with the Xentry running for an hour trying to find ...... anything.
For our cars that don’t have the electronic braking system there is no ABS line item in the modules for the car.
Once the xentry connects to the CAN, it displays all available modules that stand by for your commands.
To only thing somehow related is traction control.
In the traction control module there is a developer line item that has an actuation for something called “high pressure return valve�.
I tried that and I got a “rewarding� rattle and buzz.
I tried to actuate that while stepping on the pedal, um nothing special.

I went to the WIS, looked at bleeding, the only thing said was pumping with bleeder open which freaked me out.
I looked at the ABS section, no bleeding or actuation or reference to Xentry there.

So the explanation has to be that the references to Xentry have to be for the AMG “55 series� , with the electronic brakes.

As far as the slightly soft pedal, you only lightly tap it and the car seriously slows down. It’s just that the pedal itself seems slightly soft.

Now for the Subaru there was a master cylinder brace which firmed the pedal, because turns out that the firewall was not that rigid.

Jasonoff the screens you provided are from the DAS program.
The DAS does not cover w204, but earlier. For 204 you use Xentry which has a darker and different window.
However the 55 series AMG s would use DAS

I will have another look tonight, will look for the module in those pictures and will post the list of modules that show in Xentry

The procedure did mention Xentry or DAS, figured the menu items were similar.

http://scantoolresource.com/mercedes-benz-scan-tool/ --> In the feature set it says "ABS Service Bleed" under Chassis tools.

I could have sworn someone posted on mbworld how to do it.

I've only bled my brakes, like, a couple dozen times. And I've never had a brake-related problem. It's probably the one maintenance item that I take the most time on, checking, double-checking, and triple-checking everything. It's embarrassing how long I take to do it, but I need to make sure I'm not taking shortcuts or missing anything. But what do I know. :rolleyes:

No, you don't need to pump the brakes. No, the pedal feel is what it is until you install stainless braided lines and use a higher viscosity fluid like SRF.

That's cool man. I posted the WIS procedure. You don't have to follow it if you don't want to...

The people who designed the car designed the procedure. That's why I follow it.

Right. Section 5.2 says you don’t have to pump the brakes unless you’ve opened up the hydraulic system for repairs. With exclamation points (means don’t). Nowhere does it say that you have to actuate the ABS. For a regular bleed, I’m doing it perfectly correctly.

if you’re doing either of those things, you’re not following the instructions.

So then your abs module always has old fluid?

Nope. The Motive pressure is enough to clear it out. Just following the instructions. Did you read them?

I don't the fluid flows through the module without pushing on the MC plunger.

What you think isn’t relevant. The instructions “from the people who designed the car” actually expressly say NOT TO pump the brakes for a regular bleed. The Motive pressure is sufficient to get past the ABS seals, but too much pressure can damage them. If you have the MC out for repair and/or the system is bone dry, the procedure is different.

Thx, that may be the culprit as I'm still using the LV fluid.

The WIS instructions I posted says "It is not necessary to pump the brake pedal". I don't see where it says NOT TO... "expressly".

Did you read the instructions? Do you have different instructions maybe?

You also said not to go above 20psi. Is that in a different set of instructions somewhere? The WIS instructions I posted says to use 2.0 bar which is 29psi.

The exclamation point must not be to drive that point home, or to signify caution, but to express happiness then. Must be my bad. Do whatever you want.

Yes. No.

20psi has been working fine, but I might adjust to 29psi then. All I know is that too much pressure is bad. Thanks.

FYI: "NOT TO" and "not necessary" is very different. Doesn't mater if there's an exclamation point or not... Are you ESL?

Excellent, thanks! Was worried I may have missed something and causing damage.

No problem brah :cheers:

I almost hate to post this after the above debate but it is a fact. Last year I had removed my entire ABS module, the master cylinder, and all brake lines for the front of my C63. Essentially all the fluid was drained from everything. When I reinstalled all the lines and pieces I gravity bled the entire system starting with the usual right rear and everything works perfectly. I have had absolutely no issues with brake pedal feel or CELs. Maybe I was just lucky, but for the past 40 years and many many cars I have never had a problem with gravity bleeding.