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  #1  
Old 01-13-2017, 11:43 PM
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Leaking brake line.

Was changing the transmission fluid and being under need the car I spotted some rust on the brake line, barely touched it to inspect it and left it alone. Finished up the work when I spotted a large amount of brake fluid dripping on the floor. I already felt the brake pedal going to the floor when I was going through the gears. The weird thing is that the level in the reservoir didn't go down.

Now the question is, do I have to replace the entire line at both sides of the fitting or will just a new fitting do and how involved is this job?

1990 300SE W126




If the lines itself are fine is this the coupling I need?



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  #2  
Old 01-14-2017, 12:17 AM
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Clean and dry the area so you can tell exactly what's leaking. Hopefully it is the coupling.

If that's a brake line to the rear, you might not notice that the front chamber of the reservoir has lower fluid level than the larger rear chamber. Take a closer look.

Sixto
83 300SD
98 E320 wagon
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  #3  
Old 01-14-2017, 12:21 AM
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Quote:
Originally Posted by sixto View Post
Clean and dry the area so you can tell exactly what's leaking. Hopefully it is the coupling.

If that's a brake line to the rear, you might not notice that the front chamber of the reservoir has lower fluid level than the larger rear chamber. Take a closer look.

Sixto
83 300SD
98 E320 wagon
It was getting dark and didn't feel like more time under need the car. Will check it Sunday when I have time. If it isn't the coupling I'm sort of screwed right?
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Old 01-14-2017, 01:41 AM
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A little research and it looks like it's not that painful of a job. Looks like a little angle looked over my shoulder, could have raptured when making an emergency stop and I have some steep hills in my hood (32% grade). Does anyone know what size brake line I need.

https://www.youtube.com/watch?v=JM3rKGsd198
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  #5  
Old 01-14-2017, 03:47 AM
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Jorn, to the best of my knowledge brake lines should have no fittings in the run between the master cylinder and the individual wheel calipers. Someone must have repaired that leaking brake line in the past by adding the now-leaking coupling, instead of replacing the entire brake line.
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  #6  
Old 01-14-2017, 08:20 AM
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Originally Posted by Ferdman View Post
Jorn, to the best of my knowledge brake lines should have no fittings in the run between the master cylinder and the individual wheel calipers. Someone must have repaired that leaking brake line in the past by adding the now-leaking coupling, instead of replacing the entire brake line.
Thought it was already weird there was just one line with a coupling and was wondering why there was one in the first place.
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  #7  
Old 01-15-2017, 11:40 AM
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I'd order out a brand new set from Pelican. If one is bad, the rest are right behind it. I just replaced all of the brake lines on my 20 year old CL600. Not because they were leaking but because they were 20 years old!
Anziani
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  #8  
Old 01-15-2017, 01:20 PM
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The reason that someone took a shortcut is that the replacements are delivered as unbent lines, and it's tough to shape it, especially without a lift. You can compound the shortcut by splicing in a new length of line. Compression fittings would be dicey, but if you have a proper flaring tool and appropriate fittings, it can be ok.
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  #9  
Old 01-15-2017, 01:43 PM
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Quote:
Originally Posted by anziani View Post
I'd order out a brand new set from Pelican. If one is bad, the rest are right behind it. I just replaced all of the brake lines on my 20 year old CL600. Not because they were leaking but because they were 20 years old!
Anziani
'97 CL600 62K
You replaced everything from the ABS/SBC pump to the wheels or the flexible lines at the wheels?

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  #10  
Old 01-16-2017, 08:58 AM
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The fitting is from the factory just like the one pictured. It is highly unlikely that you will be able to just replace the fitting and not the lines also.
The part numbers for the lines appear to be A 123 420 72 28 and A 123 420 74 28. You would need for these to be looked up by VIN to be sure.
It's also very possible that the other end of the line to the rear is just as rusty as the one in your picture.

Good luck, Robert
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  #11  
Old 01-16-2017, 11:40 AM
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Originally Posted by RPM55 View Post
The fitting is from the factory just like the one pictured. It is highly unlikely that you will be able to just replace the fitting and not the lines also.
The part numbers for the lines appear to be A 123 420 72 28 and A 123 420 74 28. You would need for these to be looked up by VIN to be sure.
It's also very possible that the other end of the line to the rear is just as rusty as the one in your picture.

Good luck, Robert
Are they already pre bend? And thanks for the info, that helps.
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  #12  
Old 01-16-2017, 01:14 PM
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by the looks of the line - I doubt they are going to be reusable once you apply tools to them.

3/16 lines are cheap at autozone etc, some come preflared too in various lengths, You dont have to use the mercedes benz union splice here unless you are a purist.

If I were to repair this and it was close to an end point - I would snip this line off at a good solid point where there is no corrossion then get an appropriately sized length of new brake tubing from a parts store with correct fitting on one end (MB use metric bubble flares on ends)

cut the new line at the "other side" and double flare it with a proper nut for it - same for the line on the car and use a coupling union there (double is easier to make and its tools are easy to get). All these parts are available at any parts store for really cheap (like under 20) and a flaring tool is cheap too. Napa sell a small double flaring tool which is really easy to use under a car.

If you fancy new copper nickel lines like volvo (aka rustproof lines) and buy a roll you will need a bubble flare tool for the business end, I use an OTC brand for it, takes some practice to make good bubble flares (abt 5 or 6 times)

bending a copper nickel line is easy - the green armor line from AGS is slightly tougher to bend by hand but a small HF tool for bending the line makes quick work of it.

If you have found one point of failure in your brake lines I suspect you have other issues elsewhere too. My first bitter lesson in brake line replacement was to never swap just one line if there is rust as the probability of the whole line set being a pile of rust is close to 90%
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  #13  
Old 01-16-2017, 01:38 PM
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It's rusted out on both sides, I will most likely replace the corroded part of the line. Seems like an easy job and I'm no purist by any means. The other brake lines do look good. The fuel lines at the pump and filter have the same issue tho, they don't leak but are heavy corroded.
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  #14  
Old 01-16-2017, 05:22 PM
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The fuel lines are easier to work with as they are a few magnitudes of lower pressure than the brake. They are also available in parts stores by the foot - you will need to straighten them the best you can (which can be annoying)

brake lines are not too difficult to work with

I have replaced quite a few entire sets in different cars, copper nickel line is easy to work with and flares beautifully, the flare nuts are super cheap too.

If you bend and angle the line nicely it'll look just like factory line.

a roll is cheap online or NAPA is great for it. they sell it by the foot. You can go in any parts store and ask for a 6ft section of european fitting line by eyeballing the picture here (for abt less than 10 dollars). The european ones are for our cars and for late model GM cars.

dont sweat or waste time on undoing that union in your car - just cut the line off.
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  #15  
Old 01-17-2017, 07:47 AM
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Quote:
Originally Posted by Jorn View Post
Are they already pre bend? And thanks for the info, that helps.
All the brake lines I've replaced over the years have come unbent but they do have the fittings already attached. It's just a matter of bending to fit the car.
If you are working with the car on jack stands this is going to be a bit more difficult than with the car on a lift.

Good luck, Robert

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Last edited by RPM55; 01-17-2017 at 08:28 AM.
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