As we all know Mb recommends replacing brake fluid at 40000 miles 60,000, 80,000 etc . I believe it’s to keep the expensive antilock system good. I went to Firestone where a friend works and his big company owned scanner could not open the ABS valves . ( or the new fluid never replaces the old in ABS ) as I understand it. Does he not know the scanner? Can other scanners do it ? Or is it a MB job that only they can open .

 

A few things come to mind...

First, I know MB does recommend a brake fluid replacement as part of Service B (20,000 miles or two years, whichever comes first). Thing is, brake fluid doesn't really "wear out" but rather absorbs water (a consequence of air being pulled into the reservoir as the fluid level drops as your brake pads wear down, requiring the caliper pistons to move further out). Here's my thoughts on that. I live in the desert. Others live in Seattle or London or some other VMP (Very Moist Place). The amount of water cars in those two extremes will have in their brake fluid will be wildly different at the end of two years.

And, being cheap and lazy, and also being well (!) past any hint of warranty, I'm going to do this job when it's necessary - but not before. To that end, I recently acquired a (very) cheap tool to test the amount of water in my brake fluid. (yes, under $6 delivered).

The other thing I'll add is that I've read other say that the ABS cycling during the bleeding process isn't necessary. I kinda / sorta see how that could be the case. If you do an "old school bleed" you'll get everything but the fluid right at the ABS module / pump. As the ABS pump is activated, any old fluid left in the system will be comingled with the new fluid, presumably improving the quality of the fluid in the ABS module / pump. Yeah, that's iffy - and if you're me, you essentially never actually trip your ABS (well, until I drive to the frozen north and drive on snow and ice).

OTOH, if you have a really capable bidirectional scan tool, chances are it gives you the ability to activate the ABS pump, and (I believe) will essentially pump long enough to ensure that new fluid (from your drained and refilled reservoir) has made it out the caliper's bleed nipple. I think my tool will do that job, and I do plan on doing a brake service in the spring sometime (and yeah, probably a video).

I guess the long and short of it (in my twisted world) is that if you have zero ways to bleed the ABS system, you're still doing well by bleeding the rest of the system and flushing out as much of the old fluid as possible.

The other thought I'll leave you with is - what DOES the shop tech really do when doing a "full bleed" on our GLKs? Maybe they do the ABS bleed... maybe not (I've heard some consider changing the fluid in the reservoir a hunky dory approach). Seems to be a lot of opinions on this issue out there, so rest assured there are a lot of approaches among the professionals as well.

 

Yes once I took a different car to a mechanic to change fluid , a month later It went on a friends lift and the bleeders were full of rust untouched so I went back ! . I don’t know if the Glk was ever done right . I do want it done. I do notice a good improvement at 35000 in brake performance with new fluid , almost like new pads ! So yes it collects water .

How can anybody say activating the ABS changes the fluid . Unless you put an ABS on a bench in a laboratory and do a proper test, that statement is a mechanics bs sales pitch . Unless there is an actual test published I don’t believe it . So nobody knows . I’m sure a replacement unit installed with cheap labor will cost 14-1600, I’m just guessing . I just don’t want to need a replacement , or caliper from old fluid .
I took my Glk into a real nice shop it looked great , expensive , for a filter , transmission , converter drain. And new fluid , guy said he would do it . I went back asking why he had all that extra fluid I bought . He said they couldn’t drain the converter they were scared . But he would drain it again in a few weeks free. I don’t know , I would have gone somewhere else if I was told the truth.

Mb I don’t think recommends the differentials be changed , but brakes 4x by 100,000 miles. There is a good reason for this .

 

Don't know how **** we need to get about routine maintenance, but if it's like virtually every other fluid we "change", we never, ever get 100.000% of it. On a transmission, it's much less, even if you go to the monumental step of draining the torque converter (much harder on some GLK models than others).

But yeah, you can pump new fluid through the system with the ABS pump. I wasn't able to find (quickly) a video showing it done with a MB vehicle, but the process should be the same for our GLKs as other cars - you open the bleed nipple at the caliper, connect a hose to a catch can / bottle, and start the ABS bleed process for that wheel (brake). The ABS pump runs for quite a while, and it only makes sense that it does pump fluid through the line, into the caliper, and out the bleed nipple (which is what the process actually does, taking some of the suspense out of the discussion). ;-) Obviously, the ABS pump doesn't normally pump fluid out of the system (since it's sealed other than the reservoir) but if the process does push fluid toward the brake caliper, it's gonna come out with the brake nipple open, and can only be supplied by the reservoir - ipso facto, you just bled that brake.

Again, I suspect there will be a video on the process showing a GLK (in Arizona) this spring. ;-)

 

How do you Activate the Abs pump ? I did not know about that . Thats all that is needed I would think .

 

That's the $100,000 question. I have three Mercedes-centric "scanners." All have the ABS activation process, for brake bleeding, in the menu system. None of them will do it on the GLK. It's grayed-out or you get a message that it's not available for this model (GLK).

 

So what do I do?

 

I guess pay M-B to bleed your brakes (and hope they actually do the ABS part) or look at it the way happyguy does, in his twisted world - I'm firmly in his twisted world camp.


"I guess the long and short of it (in my twisted world) is that if you have zero ways to bleed the ABS system, you're still doing well by bleeding the rest of the system and flushing out as much of the old fluid as possible."

 

I think Habby will post a solution. Or I’m in the same camp .

 

no pressure habby...

if someone really looks into it, I'm sure the electrical connector to the ABS could be disconnected and then you manually supply power to the ABS pump and to the valve/solenoid for the caliper you're bleeding, to open it. that should pump out fluid for that line on the caliper end. just cumbersome and not as elegant as using a specialized tool.

 

Yea sounds risky and you need knowledge of wiring on MB

 

certainly you would need a factory schematic for the ABS electrics/electronics but, at the end of the day, all the fancy electronics and software apply hydraulic pressure and remove it, as needed, to the brake caliper controlling the wheel that is locked. that means hydraulic pressure and a hydraulic valve changing state to provide pressure and remove it as determined by the system.

 

I'm thinking you could do it with this (obviously TOTALLY safe process)...

1) Connect a gallon container of brake fluid with a line to your reservoir
2) Open all four bleed nipples
3) Accelerate the GLK to 100MPH
4) Stand on the brake pedal as hard as you can
5) Repeat until clean fluid covers the side and back of your car, or you die

Or, I'll check to see if my scanner really CAN activate the GLK ABS pump for purging. Just an aside, I wonder if you try to convince the scanner that the vehicle is a W204 (C-series sedan) rather than an X204 GLK if it would make any difference...

 

Ok great , or have a few drinks , freeze the driveway with hose , make it lock a few times 😬

 

I have never done the ABS, just did a bleed after a line repair and pedal firmed up after a few drives, we have had slippery roads up here already, so not sure if the ABS is kicking in and mixing with new fluid.

 

Well, looks like I was overly optimistic about the capabilities of my bidirectional scan tool - in fact, it supports only a few (Sprinter, and mainly old models otherwise) Mercedes models in the ABS bleed function. Dang.

Not sure if there's a reasonable option, but if there is, I hope to find it (suggestions are welcome, to support a future video on the process)...

 

As with many things related to our beloved Mercedes, there's a lot of information out there, but vanishingly few "answers".

I found very little in the way of definitive information on how to properly bleed a Mercedes (X204 or similar) ABS system, other than by owning a bidirectional scanner capable of it. My (quite pricey) Launch X431 Pro won't do it. My (cheap) Autophix 7770 claims to do MB ABS bleeding, but I'm going to assume it won't do the X204 (though I will check in the morning, and have an email into Autophix to see if they have any wisdom on the issue).

I did see several sources that claimed that if you use a pressure bleed system, AND pump it up to 25-30psi (a couple BAR if you're into that kind of thing) it'll push the fluid through the ABS pump, effectively bleeding it. Some mention that the ignition has to be on for this to work. Looking at the whole thing, and because a pressure bleed system is going to be (by far) the easiest way to bleed my brakes, I just . Not all that spendy, at about $50, on sale at Amazon. It (very importantly) does come with the proper 45mm threaded cap for a Mercedes (and apparently most European vehicles).

For those who haven't seen or used a pressure bleeder, it's basically a reservoir that can be pumped to a desired pressure, that forces new brake fluid through a hose into a special cap that replaces the one on your brake reservoir. No need to top off the reservoir a dozen times in the process - just open a bleed nipple, and let the fluid flow until you have only new, bubble-free fluid coming out (the kit includes a catch can with clear tubing, to make this portion of the process simple, too). Of course, you do have to make sure you don't run the pressurized bleeder dry, and keep an eye on the pressure which would decrease slightly as fluid is pumped into the vehicle. Since this is a process that should be repeated regularly (as often as every 20,000 miles or two years), spending a few bucks on a new tool doesn't bother me a bit.

And yeah, I suspect a video is coming... ;-)

 

I know exactly what it is. Why? Because I built one from scratch from components bought at the hardware store. I mostly did it as a challenge to myself. It's based on a lawn sprayer. I had a web page showing how I built it, but it's gone now.

I actually used this YouTube video to build it (this video is still around after 11 years now)

 

Nice! I do like the concept of the DIY garden sprayer approach. Though for under half a C-note, getting a purpose-built system including a catch can and the proper reservoir cap makes the prospect of cobbling one together in my garage less enticing. ;-) But OTOH, if it creates and hold pressure, and pushes fluid down the hose, it does everything the most expensive system will!

 

I actually got original brake reservoir caps for the 2001 Jeep and ST1300 motorcycle, versus buying the generic PVC cap shown in the video.

But, oh boy!! To pump it up, then go to each of the four brakes all by yourself. A complete brake bleed in 20 minutes or so, with no effort 👍

 

That's exactly what I used on my GLK a few weeks ago although I only went up to 15 psi. I have a great fear of over-pressurizing and then something bursts or blows off and brake fluid goes everywhere - but especially on the vehicle paint :-(

For $50.00 an M-B dealer will welcome you inside, offer you a seat and provide a cup of coffee while you discuss how you want to finance your brake bleeding procedure.

 

Wow a lot of good info here , wakes me up at 2:30am😀, but why worry about pumping the fluid to 20-30 even 60lb when the system sees 1000–1500 , and up to 2000 lb hard braking ? Thats what it was designed for . My 95 year old water pipes in my house get 100lb city water ! 100 lb sounds like nothing to a brake system. Ok back from dog walk more alert , it’s the plastic tank that you worry about. It looks tough, like pump sprayers that I routinely pump until I can’t , when they get clogged ! I’d guess 60-120lb . it looks like 20-30 lb will not be an issue . But I’m sure I’m overlooking something as I’m guessing.

 

Because the parts I'm worried about are the brake fluid reservoir, the cap fitting etc. Those parts, under normal circumstances, are never under pressure (other than atmospheric). If the reservoir is old, a bit brittle or the threads are maybe compromised, or the hose or hose clamp from the pressurization bottle aren't that good anymore then you could have problems. The body of the Motive bleeder is quite thick and seems strong and it's designed to be pressurized so I'm not worried about that. It's some of the other stuff after that which could be a concern. I prefer to use the minimum pressure needed to bleed the brakes.

 

I'm contemplating the best way to do the bleeding (keeping in mind I'll be doing two GLKs). My thought is to slowly bring up the pressure, starting around 10-15psi, and see if turning the key on (or not) makes any difference. If it does, I suspect that the difference could only be because of some change in the ABS modulator. I'm going to look for a pneumatic diagram of the GLK brake system to get a better idea of the cause and effect I should be looking for.