Mercedes needs to address rear brake line corrosion. My findings.
here is the link for it.
https://www.nhtsa.gov/report-a-safety-problem#index




I would think MB has outsourced these lines and the "corrosion coating " isnt doing anything at all. Hell i had steel lines on my 1965 Bug that were over 50 years old and they looked great
So why do MB brake lines fail after 10 years? No its not the effect of driving conditions. its crap steel and coating that is causing this. Prolly Electrolysis effect corroding from where the mounting clips attach to the body...dissimilar metals and all that...This is what we should expect from MB now " the best or nothing" meaning nothing and we crash now....for which we pay a premium cost to replace with the same crap product
Thread starter said it “We can see that the failures will continue to happen as more vehicles get older and more brake lines corrode.”
It’s wear and tear.
Service B Inspection.
etc. etc.
When new and in proper service order, the material choice as installed is the best per DOT and OEM.
—-
My 2005 w203 just popped a similar leak…as you describe, above/near subframe and the leak was from within a clip.
It cost me a little brake line, two unions.
If going forward, against Mercedes:
- Be prepared to show bi-annual brake fluid changes, with the proper fluid at the very least…
No OEM will fit stainless, the proper stainless at that. Between the cost and the different structural abilities of stainless v. proper steel…look it up.
Good luck.
Last edited by BF_JC230; Feb 9, 2024 at 05:52 PM.
Rich
However - they have quoted me ~$3100 for replacing rear brake lines (subframe out) and ~$5220 (!!) for replacing with subframe in.
However - they have quoted me ~$3100 for replacing rear brake lines (subframe out) and ~$5220 (!!) for replacing with subframe in.
The Best of Mercedes & AMG
Two years ago had front and rear offside replaced due to corrosion also.




I believe the cause is a combo of untreated line that is abraded in each retaining clip/bracket. Basically rust begins there from relative motion (the car driving, thermal cycling) plus dirt and debris is ground in, and the rust spreads outward from those brackets. All cars have brake line retaining brackets so I don't really understand what's worse about these. Too tight? Too loose? I highly doubt Mercedes uses "substandard steel." All cars use essentially mild steel as far as I know, though some have a coating which CAN help but isn't a guarantee. I am sure the buyer of my E63 in 2014 would have paid the $104k + an additional $250 for stainless steel lines. I don't know why this isn't a thing.
I will file a complaint. There is a chance I will just have the local shop fix this because I want to drive my damn car. Normally this would be a DIY project but on this car I am more willing to just pay to make it go away. Definitely frustrated.
Oh, the shop tech did say my subframe looked pretty good, to the point where he wondered if it had been done before.

Last edited by kevm14; May 18, 2024 at 05:09 PM.
Rolling downhill noticed that brake pedal hit the floor. Braking ability barely there. I'm still able to decelerate and safely made it home. Later realized this was bad decision as I had significant trail of braking fluid.
Fluid gushing from bottom plastic pan drain hole, right under the driver seat.
Thought recalled booster problem. Called Mercedes and carefully explained symptoms. Was cheered by adviser that it is a recall and cost me nothing to tow ad fix.
But, having history with Mercedes, last time they tow me for free, they suggested me to do repairs I did not ask for, and denying their suggestion mean I have to pay for the tow. After a bit of arguments we found mutually acceptable resolution (paying more sane price for repair I actually need).
Not to get into the same trap, checked booster and found that while slightly wet on the inside, it cannot (yet) cause catastrophic failure like mine.
Took left bottom under car pan off and found line leak like on many posts here and everywhere else. Interestingly, the only leak and severe rust is in the most front clamp, both lines. In the middle and rear clam line looks brand new with no noticeable corrosion. I found this super strange! Is this because salt spray enters from the front wheels, runs along the line and stopped at the first clamp? Is there some kind of galvanic phenomenon going on? Front section of both lines also looks reasonably good. The only problem is that one dot in the clamp.
Mine looks exactly like many others. I may post pictures later.
Calling Mercedes again. describing line corrosion. Sure enough - not under warranty nor under recall. Estimate? 24 hour or more labor (this is labor time and not work completion time) at $249 US per hour (used to be layer's rate, not mechanic's), plus raw lines (no specific p## available) at $150 each x2. With tax - $7K, US.
Called headquarters in GA, same answer, no recall, no warranty extension, no matter that cause and results are the same as recalled booster. Advised to report to NHTSA, explained that enough complains may trigger safety recall, but Mercedes will not volunteer, no matter that lifes are in danger.
I would encourage everybody to do just that, report to NHTSA, , and hopefully some day we may have all our lines properly replaced. Colleague of mine had >10yo Tacoma replaced with brand new one at no cost just because of rusted brake lines, no other problems. I guess there are many more Tacomas than MLs and Rs, to file NHSTA reports.
While waiting for the miracle, I've ordered from Amazon: liter of DOT4+ fluid, Hand vacuum pump kit (for one man brakes flush), and 3/16" brake line splicing and flaring kit, including x4 couplers with nuts and 25' of steel copper clad line. Total cost - $60 US. Took about 4 hours to do whole job. Jack and stands are enough, though lift would be nicer.
My opinion: Mercedes should do better and fix all brakes, this is people's life, health and well being. Brakes lines should not rust into shreds over that time, especially on Mercedes. And do not fear DIY, this is not difficult job. (more shame on Mercedes for charging $7K for it!)
At 140KMiles I still like my ride! :-)
Front clamp
Middle clamp
Rear clamp




Nobody should be following this picture. Do not uses compression fittings unless it’s an extreme emergency and temporary. This is not a permanent or wise solution. I wanted to consider this when I had zero dollars to my name on a rusty piece of crap crap dodge ram and even then I knew better.
Do not spread the panic, buddy. This is not compression, this is double flared the way it should be.
I would not drive with compression fittings on the brakes.
Here is . After some practice it does very decent flares, and they do not leak on fist attempt, and I put my whole 200 pounds on the pedal with engine/booster running, after bleeding it.
As a fact, I do not think compression will work on original lines at all, They are painted and slightly pitted. For compression to work even initially - OD must be perfectly smooth. Whoever to try it - will find out very quickly that stopping initial leaks can be a problem.
And OP topic is about Mercedes quality problem, not about repair.
Cheers!
Last edited by Sal.B; Aug 23, 2024 at 10:41 PM.




... rust begins there from relative motion (the car driving, thermal cycling) plus dirt and debris is ground in,...All cars use essentially mild steel as far as I know, though some have a coating which CAN help but isn't a guarantee..

As much as I know, presently, European made Mercedes use Nickel alloys for brake lines, those are also highly resistant to corrosion.
US has old tradition of using mild steel for brake lines. This is very old American problem across many brands. Mercedes models prone to brake lines rust are mostly US made and so - they are procuring locally available materials. And few that are not and have rusted brakes - probably procured US spec brake lines.
Original lines on my R350 have very thick enamel. Rusted point has enamel degraded. I think this is the beginning of the line failure. As kevm14 mentioned, motion of the line in the clamp possibly wear enamel and exposes steel. The mystery here: why on my car, and as much as indicated by search - everywhere else, it is always only first clamp. I can only imagine brine runoff. Galvanic nature is less likely as brake lines are insulated and other two identical brackets are on the same circuit but do not have corrosion.
Replacement lines: I bought cheapest lines to see how it goes. lines are available of any kind you may desire. Most practical are Nickel alloy, they feels very similar to mild steel but much more corrosion resistant. For my car, at 140KMiles, every day it is still in service is a gift. I will monitor wear on lines and will replace again when necessary.
I also plan to coat couplers with Rustoleum hammered paint. Couplers/unions, have a moisture trap that may retain water or brine, that may once again to cause premature failure. I believe that filling these gaps in the couplers with Rustoleum will extend coupler's life.




Are those the same fittings that will connect to the flexible lines?
While doing the work how did you prevent all the brake fluid from leaking out after the line was cut?
I have been keeping up with flushing the brake fluid every 2 yrs. Its very easy with the pressure bleeder. I did it earlier this year and have around 1/2 tin left over so i'll probably do it again next year instead of just wasting it. I looked at the fluid i had left over from 2yrs ago and it still looks brand new, identical with the new tin I got. I get the Mercedes brand dot4+ on ebay for around $15 a liter shipped.
Last edited by TimC300; Aug 24, 2024 at 08:21 PM.




As much as I know, presently, European made Mercedes use Nickel alloys for brake lines, those are also highly resistant to corrosion.
US has old tradition of using mild steel for brake lines. This is very old American problem across many brands. Mercedes models prone to brake lines rust are mostly US made and so - they are procuring locally available materials. And few that are not and have rusted brakes - probably procured US spec brake lines.
I did not try to prevent fluid loss while working on it as most was already lost. Bleeding brakes it took whole tin and then I had to recycle some that I collect initially. In a hind site - should get 2-liters.
Definitely need 4PLUS. Viscosity of 4 and 5 more than twice of 4PLUS.
Image above is not mine, but this is very probable condition of unions I use after winter or two.
To extend their life, even if just a little, I spend another $10 for WD40 no residue cleaner de-greaser, washed my new assembles, blow dried all with HP air gun, and saturated it all with Hammered Rustoleum.
Last edited by Sal.B; Aug 25, 2024 at 09:29 AM.
https://www.copper.org/applications/...ube/brake.html








in that I did not zoom in to see the above repair was done with flared unions, which can be acceptable. I still stand by replacing lines as a single unit. I’ve never found any trusted mechanic of mine to recommend a repair vs replacement. If a line broke or leaked once, the second disaster could be just around the corner. After blowing out brake lines on both a big dodge ram and a landcruiser, I will only replace items with corrosion, and not repair them. I surely would immediately replace a full line on my 13 e63 if there was even a weep. I’m not interested in take failure at triple digit speeds. Fortunately not a spec of corrosion…
For those with lots of subframe corrosion, do you religiously wash your cars after salt events? if not I’d get really friendly with some fluidfilm (preferable because it weeps into crevices vs cosmoline which does not). Can fluid film the insides of any metal components, then use something dry on the outside like cosmoline.




