Awesome !!! So happy to hear it.

So where is the actual leak at the MC ?
The interface MC to Brake Booster ? or somewhere else ?

 

Pierre, good job re-plumbing all your lines!! You're not the kind that backs down when troubles ring.


Your experience calls for a thread to coat all the unprotected steel lines.
Many folks drive in the rust belt... I am in dry California.

 

Yes, thats exactly where, it was impossible to see, but the end of the MC was wet with fluid when I removed it, but luckily there's a seal at the brake booster.

 

Thanks Cali, but now that I have done it, I would be faster next time! And more aware just how time consuming it is! I know you'll be happy, I had a can of black rustoleum left from something, I did spray them! But they are Copper-Nickel so I don't know how effective it will be, LOL. Slow and steady wins the race, but I'm hurting today, got the wheels back on and went for a ride after my buddy came over to help with the bleed process, I used about a liter and a half of fluid.Finding the original leak was hard, it was only dripping when the brake pedal was pressed or in the hold function, go figure. But you guys helped immensely and I'm glad to share the accolades!

 

Glad to hear your diagnosis was correct, and you were able to fix it.

I can relate on the body aches from crawling under and around a car. Although I still enjoy doing my own car maintenance, there is a price to pay. But I worry that when I stop doing this kind of projects, the price on my body will be higher.

 

I'm too happy for you , thanks for update on that issue as well.
Nice to see such handy and skillful members like you
Happy Driving

 

I have almost 130,000 miles and plan on taking a trip out west to see my daughter. Changing Regular Maintenance items for a 12 year old car with 130,000 miles is not unusual. Especially when you are going over 2,000 miles and are in bad terrain for a Mercedes-Benz dealer near by? I am 67 years old and last time I had my Benz in the Dealer for Service was 2017 at 90,672 miles on the last of 3 service plans I had when My Wife bought a service plan on it seeing I just hot done less than a year from Cancer treatments from Stage 3 Non-Hodgkin's Lymphoma losing 14.5 inches of my small intestine and 6 surgeries. I have done all the service since 90,672 miles. I am due for Transmission Service which I planned a month ago but spent 3 days in the hospital with Congestive Heart failure caused by the Chemo Drugs from 11 years ago. It seems every time I have time to work on My Mercedes-Benz E350 my Daughter's Lexus or My Wife's Audi Q5 needs something especially the Lexus RX350 with 183,000 miles on it. I know Pierre is trying to fix his Car but before buying it some parts do wear out and on a Mercedes it CAN be costly to repair especially if you cannot do some DIY maintenance?

 

Amazing work, Pierre! Climbing under these cars on jack stands will beat you up. I've had the TR8 on stands probably 10 times and at least it's light enough to get up and down with my shop floor jack. I can't imagine doing what you did on that Mercedes. You significantly scared me with this brake work that I sold the E550 today. The used car market is still pretty good and I decided I have the Triumph to wrench on and other cars to drive around town. Retirement has diminished my driving significantly and I really need a more versatile vehicle, like a small pickup (not a 150K G-Wagon!) Living in a 120-year-old house requires constant trips to Home Depot.
Once again, Way to tackle that job head on!

-Keith

 

Sorry to read that you've sold your E550, Keith. You've volunteered a great deal of information and help on the W212. Although we need no help with a TR8 (LOL) I hope you stick around and contribute from memory.

 

Thanks Keith, it was an epic undertaking, LOL. Sorry to hear about your loss, but I do understand, retirement changes our lives hopefully for the better, I've never been busier and don't know how I had the time to work! You've got a wonderful little car there, I remember lots of time working on mine with my kids when they were teenagers and driving them daily.I've put total of 700 miles on my '12 this year, much going to Home Depot! I could use something more utilitarian also, I'll keep the '12 and sell the '13 when the wife retires. You've also been a long-time great contributor to this forum, many, like me have greatly appreciated your contributions, I wish you all the best and hope from time to time you stop by and say hi to us here!!

 

Thanks, I agree, gotta keep doing and moving, I'll be 64 this year and rolling around on a creeper is not the same as when I was 40!

 

Pierre,

Did you get to bleed air out of the ABS/ESP hydraulic unit ?
When I lost my fluid due to the plug coming off and at least 500cc or more brake fluid was lost, air got into my ABS/ESP hydraulic unit, lets call it HCU.
I assume you doing new brake pipes would be the same as my case, which is air introduction to the HCU.

Xentry is required to simulate an ABS pulsation.
I do not know what is wrong with MB Xentry designer, the menu title for ABS pulsation activation is SBC HOLD ... !! Dugghhhhh
Also why only LEFT side brakes, I do not know. It could be wrong description too by Xentry designer

Above actuation gets our pedal to pulse like a true emergency ABS activation and with the strong noise.



This one below turn on the motor, but I do not know if any of the 12 solenoids are open or not. No pulsation to brake pedal whatsoever.




This one below is only a mild CLICK, solenoid click




I had to bleed twice.
1st time I got on my LEFT FRONT caliper, micro bubbles so plenty, it looks like those nice foamy black beer Guiness Stout froth.
At first I thought my brake fluid was contaminated with some other "oil", I waited for like 60 seconds and all the micro bubble gone and brake fluid looks normal....wheeewhhhh.

2nd time was final after I ran 2 liters total on all 4 calipers, I got 2 big air bubbles still, from the FRONT LEFT.
My naughty Xentry for some reason is being naughty, it kept crashing after I did SBC Hold activation . So wasted time booting up the Xentry again and again.


The need for air bubble removal, caused to me do some reading.
I wanted to know where are the potential air pockets inside the HCU.
WIS for W212 has no hydraulic schematic, only electrical one for ESP/ABS.
So I looked at 2 generations ago, W210 which is what our W212 is using or 99% similar. The W211 SBC is not useable as a reference as it was different.

I believed the air pocket is at item 11 ( Low pressure accumulator ) which is probably no more than a few milliliters just enough to push each caliper's piston/s maybe 1mm only




Without actuating the SBC Hold ( ABS pulsation ), I also believe that the green zone I marked as OUTLET will store air pockets from y7 and y9 at least up to y22 and y23 ( ( A7/3y22 and A7/3 y23 ) Front or Rear Axle inlet solenoid/s.
I could be wrong on which circuit is INLET and OUTLET, but item 11 accumulator is commonly at OUTLET line and not INLET line.



I tried to compare W210 schematic which is a hydraulic schematic, to W212 which is Electrical Schematic to see common parts.



Attached original W210 and W212 documents too. ABR = Adaptive Brake , hhmmm so many unique terms.

Hope this helps if your HCU indeed has micro air bubbles.

 

Oh Surya, you're gonna hate this, I disconnected the battery and we bled the brakes! Took about a liter and a half, none of that was necessary, I pumped and held until I got zero bubbles then closed the bleeders. I have been driving the car for a week now, great pedal no warning lights or issues at all. My buddy who came over was a ASE verified master technician and had done a few of these before, so I felt comfortable doing it this way. I do have an Icarsoft MB2, but did not need it ,nor do I think it is capable of the process.

 

Lucky you Pierre, that is good news
The bubble sensation I speak of is very very minute ( the one caused by 2 big air bubbles ), the first plenty of micro bubble froth was totally obvious.

 

Yes, when I was done I had pushed a whole Quart through the system, no bubbles solid stream

 

I will always remember this thread..... thus I am coming back to it
It goes to show that anything with rubber o-ring or seals, has a fixed life span.

When my rear single piston ATE piston seal and dust boot kit arrive ETA 12th October 2025, I thought I would be golden having all potential seal leak sorted out on my 11 years old car, albeit 43,000 KM only.
Done the front 4 pistons Brembo repair kit few years ago.

I then remembered that the Master Cylinder has seals too and of course this thread.
Have ordered from MB Indonesia and it would be 60 days wait or end of November 2025, price US$563 ( right hand drive MC ) and its 2.2x more than USA price of U$250 ish ( left hand drive MC )....usual throat slaying MB Indonesia.
Since I am keeping my car to 20 years, this Master Cylinder must be on the refresh list too.
I did not yet order the brake booster assy, as I am hoping it has less severe duty being a suction zone and no brake fluid involved.

I can then tear down the old MC and see if I can source from 3rd party the suitabe seals and keep it as back up.

What I worry is, if my MC leak the brake fluid into the brake booster, I get collateral damage.
It seems the brake booster cost is US$500 ish in USA with 28% discount off the MSRP, that meant it will cost me US$1,200 locally...duggghhh.


.




While this tech note from Cali is comforting, still brake booster damage is a risk.

The low brake fluid level alarm is worth probably 100cc too.


---------


The desire to keep an aging car to 20 years and RHD version.... as brand new car feel as possible is starting to pile up $$ by 10 to 14th years of age.
But I guess there is a nice reward to it when we can achieve zero breakdown, while car feels tight all the time like new.
As for me, there will be no more MB cars to replace my W212 E400.

I do not like dumb-azz mild 48V MB hybrid or PHEV or whatever hybrid,
I do not like any 2.0 liter engine or smaller from MB.
Above 3,000cc is not for me, the luxury tax is not worth it.
4 wheel drive also get extra tax.



AMG GT53 is within 3,000cc , so tax is lower than the 4,000cc true AMG engines.
The C63 S e-Perf is the pu-ssy 2,000cc 4-cylinder engine with hydbrid WTF....thus it is cheaper on the tax.

Anyhow, the amount of electronics on newer cars terrify me.
Oldie 2014 S-Class S400 W222, its COMAND head unit N40/3 cost US$5,500 to replace, it went banana and lost its memory, can't activate Code 810 amplifier, can't activate rear camera and can't activate
rear entertainment system....damn !!! How I know is because I troubleshoot this car for my Indie and MB Indonesia confirmed my findings.
68 total electronic modules this W222 has, mine has 47 only.


.

 

Yes, I lucked out, the MC was leaking, but there was no fluid in the brake booster, so I have it in the basement, also since I hit the 2 button on the MC order, I have an extra master cylinder also, Ididn't send it back as I have the "12 also and may need it someday.

My '12 now has a leak by the rear differential, I was sitting at a light with the brake hold on and started rolling forward! got home and looked underneath, so now I will be doing the job again! Or maybe taking it to my Indy, don't know if I'm up to this a second time. My '12 has 32k miles and has never seen salt or snow, in fact I can only remember using the wipers in rain twice, I think these lines were just prone to rust no matter the conditions, my '13 was in the salt and snow for 11 winters before it rusted out

 

With MB cost cutting method I been seeing for parts inventory in MB Indonesia and life span of part availability MB Germany for RHD cars no more like the old days of 20 years surely parts still exist,
I am really worried.

I bought a used engine computer already at Ebay, but I do not know if it is working or not as it has to be virginized first and then coded....still a long process.

Car manufacturers now seems to enjoy cutting spare parts supply availability as short as 10 years from car model date of introduction....in order for our cars to be in the junk yard soonest...

 

Right at the back of the master cylinder, but dripped down the outside of the booster, not inside, there is a gasket but once the mc is off it looks sealed, but evidently sometimes it leaks inside

 

Thanks! it was a big job for an old man on the floor with a creeper, I don't know if I will tackle this next one, on the '13 I went from front to back, 30' feet of brake line or so.

 

Pierre, can you spray coat your steel brake lines with a protectant (silicone, oil or ??) or de-oxidize the lines with a chemical de-ruster if proven effective.

It's funny how Mercedes high-tech Bosch ESP/ABS brakes are plumbed with the cheapest rusty steel instead of stainless steel.

 

Well, it's too late for the 212's I have all new rear lines on one and now need to do the other, the copper nickel lines will be fine for another ten years I would suppose, I may take some preventative measures on the GLS as it has the same green metal steel lines. This surprises me greatly as that car has never seen salt or snow,

 

You know air humidity condensate rust from the inside out.
Rust the rear caliper bores and the brake lines.

The new DOT-4 absorbs more humidity than former DOT-3 formula.
How nice it would be to have desicant built-in the MC cap! Serviced every now and then.

 

Let see where the leak can happen and when it can enter brake booster...........

Typical brake MC


.










O-ring #1 is vacuum seal, MC to brake booster interface
O-ring #2 is prevention of fluid leak to outside of MC, this one will be the one sending brake fluid into brake booster internal if indeed leaking.
O-ring #3 2 pcs belonging to the fluid reservoir.

If #3 leaks a bit and the side nearest to brake booster, it may not be visible to the naked eye, except it will pool somehere below.

So yours probably leak at o-ring #3 ( the one nearest to brake booster ) ?


We can buy stand alone only 2 o-rings ( seals ), the #3 o-ring as item 110 and the #1 o-ring as item 120.






Buying the complete MC item 100 , includes item 110 and 120, and the 2 bolts item 130.


========


The Motive brake fluid feeder bottle has a pump capable of 30 psi easy, I think I can use their pump for test purpose, testing o-ring #3 integrity, and that meant also it will test all
steel pipe interconnection integrity from MC to ABS to 4 calipers. Perhaps we use it like how we test radiator pressure, keep 15 psi for 4+ hours and see what happen.

On my W212, Motive brake fluid feeder under 15psi will flow brake fluid to all calipers thru pressure with engine off, but for reason I do not know , my friend's C200 W204 does not allow
brake fluid flow using 15psi from Motive pump alone, it needs engine running and traditional foot pumping. Maybe the ABS solenoids in closed position with engine off ?

----

I inspected the fluid reservoir cap, it has no actual seal using soft seal.
It is hard plastic to hard plastic only, as sealing.


.

 

true, but the car has 33k miles and the brake fluid has been changed 4 times