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1993 300TE, 1995 E320 Wagon
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Discussion Starter #1
Howdy all-

Well, Murphy was watching me do a front brake job today, and decided to cause some trouble. Apparently I haven't skinned my knuckles enough in payment to the mechanic gods. I wanted to change out the brake lines, and the rears went fine. The front left line however, was not going to let go for anything. The smaller (11 mm) nut on the top is thoroughly embedded into the larger cup/nut on the bottom, and the upshot of it is that I forced it a bit, and the wrench slipped, rounding the edges quite nicely :banghead:. I put some PB blaster on it and let it soak in, but nothing doing. So rather than completely destroy the nut any further, I've retired with a beer to mull over the options :surrender:. Thing is, I don't really know what options I have. Do I simply need to let the PB blaster work its way in some more? Is it possible, assuming I can get the nut off somehow, to replace just the nut? Is it possible to replace the one line? Am I SOL with this? Any suggestions?:dunno:

TIA

Dave
 

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That stinks....been there, done that on the rear. I got lucky having several parts cars and was able to pilfer what I needed. When I asked about new parts they seem to sell the lines new unflared with nuts and you'd need to get them flared somewhere. Or you can get one at a wrecking yard. I'm sure I have a front one on my SEC parts car if you can wait and can't find out, just let me know. I haven't taken the front lines/calipers/etc off yet but was planning on it anyway.
 

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CH4S Admin , Outstanding Contributor
1985 500SEC, 1991 190E 2.6.
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40,174 Posts
Sorry to hear that Dave. I can loan you my flaring tools.
Cheers
 

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2009 SL65, 1998 CL600 (sold), 1989 560SEL (sold)
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403 Posts
When I did my 560SEL I had to destroy the metal spring clip and plastic wire holder so that I could get the wrench on 100% of the nut. I then bought a replacement clip and wire holder from the dealer. I also heated the nut a bit with a oxy-acetelene torch. I don't recommend this unless you are going to replace the flexible line as well. Be carefull that you don't set the undercoating on fire.

You can get replacement brake lines from the dealer that are already flared with nuts but they are not pre-bent. You would have to get a tubing bender. The line on the drivers side wouldn't be too difficult, but the passenger side is one long piece that routes under the sway bar (behind the first firewall).

I suppose you could cut the old line 4-6 inches from the nut, re-flare it and the make a patch section and join them with a coupler.
 

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1993 300TE, 1995 E320 Wagon
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1,895 Posts
Discussion Starter #6
I got a quote on a new brake line today from the dealer for $15, which seems quite reasonable. The labor cost to have them install it was estimated at 1.5 hours ($200 "worst case"), but I'm going to hold on to my cash for a bit longer. I'm also going to get a quote from my local mechanic (the highly regarded Enrique of Mr. MB Motors). If he'll do it for $100 or so, I may just take the easy way out of this.

I'm kind of intrigued with trying to do most of the work on my car, and since the line is not leaking now, I'm going to keep driving it until I can get my mind around actually doing the install myself. Granted, I'll need a tubing bender, but bending in a new line seems a lot easier than fighting the original out of a parts car (and then trying to insert it in through all the twists and turns). I've also been reading up on flaring tools, and I'm a bit leery of trying to cut the line back and reflaring it. First of all, it seems to be a rather "specialized" talent to do it right, and second, there's just not than much room to play with in the wheel well. So thank you for your offer, Markus, but if I do the replacement, I'll be going with a new line. I'm going to have at the nut one more time tomorrow, and if nothing moves, I'll have to decide what to do.

I'll post some pics if I end up doing it myself.

Dave
 

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1991 350SD
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40 Posts
I have encountered the same issue from this old thread and was wondering if anyone might have a MB part number for the front passenger brake line. This is not a job I look forward to but the 11mm nut on the hard tubing is shot and I'm going to have to replace the line on my car. I have a 1991 350SD. I live in a third world country (New Mexico) and the dealers here are less than willing (able) to pinpoint the part for me. What a difference a state makes. When I lived in Dallas, I could swing by Park Place Mercedes on a Saturday morning and have the part identified, ordered and delivered in a week. Any help is greatly appreciated.
 

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Premium Member
1999 500SL, 1988 SEC
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1,200 Posts
My guess is the line goes back to the antilock brake and it will be a challenge. What I would do is get a section of new line, find a place you can hide a connector or union, add a new piece of line with a new fitting on the end. You could even use stainless line. Otherwise a lot of work
 

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Moderator
1991 500SEC 50K mi. 1987 560SEC Now 153K mi. 2020
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4,412 Posts
Carlos,

In addition to the above, I looked and got these results depicted below.

From the copy: "Hydraulic Unit" I believe indicates the ABS unit.

MBL

Screen Shot 2020-01-21 at 6.01.16 PM.png
 

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1991 350SD
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40 Posts
Carlos,

In addition to the above, I looked and got these results depicted below.

From the copy: "Hydraulic Unit" I believe indicates the ABS unit.

MBL

View attachment 2617881
OK. Based on the (as usual) great help from Forum Members, identified the part as 126-420-87-28. This will probably be the easy part of the task. Trying to remove the old line and replace it with the new seems nigh on impossible. I can't even find any mention anywhere on the web of the actual procedure. My guess is no one would ever do it if they had half a brain (which I'm beginning to think i'm not in that camp).So the next best option, as mentioned by Stutz, is to make an intersection but that involves flaring steel brake line in a tight space. I would be challenged to make a great flare in a vise. This may be one of the times that I have to break down and hire a mechanic. I think I'll have a bit of scotch and ruminate on the issue for awhile....
 

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1991 350SD
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40 Posts
OK. Based on the (as usual) great help from Forum Members, identified the part as 126-420-87-28. This will probably be the easy part of the task. Trying to remove the old line and replace it with the new seems nigh on impossible. I can't even find any mention anywhere on the web of the actual procedure. My guess is no one would ever do it if they had half a brain (which I'm beginning to think i'm not in that camp).So the next best option, as mentioned by Stutz, is to make an intersection but that involves flaring steel brake line in a tight space. I would be challenged to make a great flare in a vise. This may be one of the times that I have to break down and hire a mechanic. I think I'll have a bit of scotch and ruminate on the issue for awhile....
Carlos,

In addition to the above, I looked and got these results depicted below.

From the copy: "Hydraulic Unit" I believe indicates the ABS unit.

MBL

View attachment 2617881
Carlos,

In addition to the above, I looked and got these results depicted below.

From the copy: "Hydraulic Unit" I believe indicates the ABS unit.

MBL

View attachment 2617881
When it rains it pours. While researching the best way to resolve the hard to flexible brake line junction issue, I had my V belt mysteriously separate (a big chunk came off) on one edge. Upon examination of the V belt tension system, I found that the tensioner lever had crapped out and most likely changed the angle and this extra strain mucked up the belt. So I ordered and replaced the tensioner lever, the damper, the spring and the idler pulley to make sure I wouldn't have to address this for another 100,000 miles (or so). Now back to the brake line. I am going to cut off the hard line in the wheel well and flare the end, hopefully successfully. I've flared tubing before in a vise and it's pretty straightforward but before I start to dismantle things, I want to have everything I need on hand and that's where I need some input. The OD of the brake line is 5mm. The tubing appears to be coated steel. Does anyone know whether the flare on these lines is a double or a bubble? I would guess double. I am going to have to invest in a flare tool that can work in the wheel well effectively. There are many styles and brands out there ranging from really inexpensive to $300 or so. My experience has shown me that I generally don't want the cheapest or the most expensive. Somewhere in the middle usually works. For those of you who are experienced with flaring tubes, do the kits usually come with decent instructions? Is de-burring the line a critical step? Can you get a good flare without the help of a vise and plenty of elbow room? Is one style of flaring tool better than another when doing lines that are still on the car? Any help from you all would be greatly appreciated.
 

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1991 560sec. 1969 280SL
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1,133 Posts
You can get flaring tool for probably less than $20 at Napa and buy decent little adapters that you’ll need for different flare types in a kit. Don’t go spending a whole lot of money on the tool. You will pay more for those little bits you use to form the double or bubble. Also get a small tube cutter made by little imp to cut the tubing to size, when you use that there will be no burrs.
 

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1991 350SD
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40 Posts
You can get flaring tool for probably less than $20 at Napa and buy decent little adapters that you’ll need for different flare types in a kit. Don’t go spending a whole lot of money on the tool. You will pay more for those little bits you use to form the double or bubble. Also get a small tube cutter made by little imp to cut the tubing to size, when you use that there will be no burrs.
Thanks gogi. I ordered the Imperial tube cutter and will head down to NAPA tomorrow. Making a flare can't be that difficult. Just gotta take your time and have the right tools....
 

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1991 420 SEL
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201 Posts
An old trick learned from old guys in the rust belt: penetrating oil, maybe a little heat, and vise grips. Using the vise grips slowly rock the nuts back and forth, back and forth...

Not ideal but it often works.

Pete
 

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Registered
1991 350SD
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40 Posts
An old trick learned from old guys in the rust belt: penetrating oil, maybe a little heat, and vise grips. Using the vise grips slowly rock the nuts back and forth, back and forth...

Not ideal but it often works.

Pete
Thanks Pete. I've got a replacement line on the way but it looks like I will have to also remove the ABS control unit to really see where the R front brake line is routed. If it looks too difficult to actually replace the line, I'll nip off a bit of the old line and see if I can put a decent bubble flare on it. I'll have to continue to destroy the existing 11mm line nut to detach everything. I'm hesitant to use heat with brake fluid still in the line. I've got relatively new brake fluid in the system so the boiling point should be in the 400 degree range but a little heat will get there pretty fast. Have you ever used heat on this nut while still on the car? Any difficulties?
 
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