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2014 E550 Coupe
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Discussion Starter · #1 ·
Hello all!

It seems I have somehow made the egregious error of getting air in my braking system following front rotor + pads and rear pads replacement recently. I did not let the reservoir run dry (or even low!) at any point, however here I am. Main symptom: brake pedal pressure normal-ish when key off, falls almost to floor when car started. While driving, takes a quick pump or two to build pressure, then brakes nicely.
I have a Motive Power Bleeder, set to 2bar and bled in proper order from rear right. Probably 12x. Have tried the old 2 person method, multiple times. I do occasionally get a few air bubbles by either method, and sense a bit increased pedal pressure, but not significant or for very long. I have tried vacuum bleeding as well
From all google research, the ABS module can not be cycled without MBStar and yet seems my only next step...? I ordered a replacement brake master cylinder, however I have yet to install...

1.) Would anyone advise any steps I may have missed, or suggested next steps short of trip to dealer? They already gave me attitude on phone for doing my own brake job (how dare I!?)

2.) Any kind fellow shadetree wrench in KY area that might explore ABS cycling through their MBStar copy?

Much appreciate any helpful feedback!?

Jay
 

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Discussion Starter · #2 ·
@rudeney Hey friend, been a while...any thoughts on this one sir?

Some folks online claim that when 2bar pressure applied via Motive bleeder at reservoir, fluid will push any air out of ABS system...I kinda doubt that, but would be happy to be proven wrong!

I didn't note above, however I often hear some kind of noise behind/above backseat when first applying the brakes after starting car (ex backing out of garage). Sounds (in my head) almost like a brake line thwacking the rear sill/trunk. Not sure if this would be indicative of some faulty h/w or just the air being moved around in lines...or something completely unrelated and yet quite coincidental
 

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CURRENT: 2011 SL550 FORMER: C300, ML350, CLK550 Cabriolet, C240, ML320, 300TD
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Bleeding the SBC system does require SDS, (MBStar) but your car doesn't have that - it's just a typical ESP/ABS system. I find it easiest to flush and bleed with a helper pressing the pedal as opposed to a one-man bleeder like the Motive.
 

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Discussion Starter · #4 ·
Thanks Rodney. I just cannot figure out what I am doing wrong in bleeding process then, hmm.

Do my symptoms potentially indicate bad master cylinder? I already have the replacement part, maybe I go ahead and throw that part at it next?
It seems odd to me that I have strong pressure when car is off, then falls to floor with ignition.
I have also considered going back through my rear pad job, as perhaps there is a seized caliper or something…?
 

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How much fluid have you run through the system? It hold less than a liter total. If you'd run that much through, then you should have evacuated the air. If there is still air, then you have leak in the system somewhere.
 

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Discussion Starter · #6 ·
How much fluid have you run through the system? It hold less than a liter total. If you'd run that much through, then you should have evacuated the air. If there is still air, then you have leak in the system somewhere.
Definitely at least 1L…I think 3 of those Pentosin tall cans. It holds pressure when the Motive is hooked up. Sounds like I’ve got a fun one on my hands. Dangit
 
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