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  #1  
Old 10-18-2020, 05:43 PM
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Rear Hard Brake Line Removal

1985 300 CD

Trying to remove my right rear brake hose I have some across the most stubborn flare nut I have ever seen in my life. First I tried freezing it, then I tried vibrating it, then I put a heat gun to it, then I tried a torch. All the time applying copious amounts of penetrating oil. No luck.

I am going to have to cut the bugger out and replace the hard rear brake line.

First problem, there is a retaining clip that goes between the flare nut and the hose end. Normally you can just cut the hard brake line, but this time I have to get through that clip. Any suggestions? Looks like I need a cut off wheel, though access is a real problem.

Second, it is either buy a new brake line from Mercedes, which will be great if they are actually available, OR I have to make a new line. There are "kits" available on eBay which come prebuilt to various lengths with the flare nuts installed. Has anybody tried these before?

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  #2  
Old 10-18-2020, 06:11 PM
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Been doing this stuff for decades and just recently tried NiCop lines, I'm never going back to steel lines. Go to an auto parts store and get some NiCop line and metric fittings.
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  #3  
Old 10-18-2020, 07:11 PM
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Worth a try before starting to cut stuff up maybe, but I have had good luck with using a thick snapon flare wrench (you can usually find them used on ebay) and tapping with a hammer.
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Old 10-18-2020, 07:36 PM
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Quote:
Originally Posted by Sugar Bear View Post
Been doing this stuff for decades and just recently tried NiCop lines, I'm never going back to steel lines. Go to an auto parts store and get some NiCop line and metric fittings.
What size and kind of flare do these old beasts take? Is there a tool you recommend?
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  #5  
Old 10-18-2020, 07:44 PM
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Yeah, I have the 11 mm Snap-On flare wrench. It was no match for this flare nut!

I tried the "impact" method with both a hammer and a vibrating multi tool, no luck.

The retaining clip, and the limited access, makes grinding this nut off close to impossible. I am going to have to rest off a few days frustration before getting back to this thing. I supposedly do this for fun, but sometimes I really wonder........
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  #6  
Old 10-18-2020, 11:01 PM
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Try a 7/16". It's bit tighter fit than an 11mm.
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  #7  
Old 10-18-2020, 11:13 PM
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Quote:
Originally Posted by moon161 View Post
Try a 7/16". It's bit tighter fit than an 11mm.

11mm = .4331"
7/16 = .4375"
looks like 7/16 is looser!
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  #8  
Old 10-19-2020, 01:16 AM
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okay, here are some handing tips:

1. Penetrating oil is Kroil, CRC Freeze off, and also WD-40 Special Penetrating Oil
2. Freezing means hitting it with CRC Freeze Off until it is cold. I used a heat gun first, then hit it with Freeze-Off. This has worked for me in the past.
3. Vibrating is with a special multi tool meant to vibrate the nut. This is sold by the man who shall not be named in Bellingham. And it is genius! Too bad it did not work. However, every other hose-flare nut quickly surrendered using this gem.
4. Genuine Snap-On 11 mm flare wrench, only the best will do!
5. Used a propane torch as a last resort. Did not work.
6. I found an outfit called EZ-Fit which will sell pre-made NiCopp brake lines in any length with the bubble flares and 1.0 X 10 mm flare nuts. The NiCopp lines can be safely bent by hand without kinking while you are under the car! The NiCopp lines are OEM on some German cars so I can trust them.

So it looks like I am going to have to cut offending flare nut off with a Dremel tool. It will probably take an hour or more. Then I can replace the hard line with an EZ-Fit line and reassemble the brakes. What a hassle!
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  #9  
Old 10-19-2020, 01:55 AM
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Before doing all that i'd go for more torch time. Perhaps let some Kroil soak in overnight, try to break it free, more penetrating oil, torch it a LOT, more penetrating oil, torch, hit with a hammer, torch, then try breaking it free.
If you're gonna cut the hard line, you got nothing to lose
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  #10  
Old 10-19-2020, 03:36 AM
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Use two wrenches, the 11mm flare wrench on the top fitting and another flare wrench as a counterhold on the bottom brake hose fitting.

If the top flare nut in your case looks a little rounded, put a little rubbing/lapping coumpound on it before applying the 11 mm wrench (to get a tight grip on the fitting).

Try to tighten the the union first. just a little tighter is all you need.
Sounds counterintuitive, but tightening it may break the corrosion seal on the exposed portion of the threads.

Once the corrosion seal is broken, you should be able to break the addtional clamping torque you applied by tightening the fitting
(now that the extreme clamping force of the corrosion seal has been removed), without further rounding the flare fitting.

Best of luck
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  #11  
Old 10-19-2020, 01:41 PM
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If someone has not previously mentioned it European cars have a bubble flare and the US Cars have a double flare. The flaring tools are different and neither costs that much. I got my bubble flare tool for around $28.
Don't know if the bubble flare kits have made it to the free rental tools at autopart stores.
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  #12  
Old 10-19-2020, 01:50 PM
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I tried the idea of tightening the flare nut, it did not help. How that thing got so welded in there, I don't know. I typically assemble these hydraulic fittings, and the bleed screws, with a light dab of Krytox 205 grease to avoid this problem.

What I am going to do before the Dremel is to cut the brake line above the flare nut, then get on the nut with an 11 mm 6 pt socket and some "Grip It" paste (similar to valve grinding compound) and go at it one more time.

If that doesn't work, then the Dremel is the last resort to remove the flare nut. The retaining clip is the problem with removing the hose after the brake line is cut. If it was not for the clip, then I would just have to cut the brake line.

There just comes a point when I run out of options.
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  #13  
Old 10-19-2020, 02:15 PM
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I only use vise-grip pliers on brake line fittings anymore. The metal is somewhat soft and the corrosion layer is enough to round the fitting off with normal force. I've not met a fitting yet that didn't come off with the vice-grips. The key is to support both sides of the fitting and get those vice-grips TIGHT.
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  #14  
Old 10-19-2020, 02:29 PM
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Quote:
Originally Posted by Diseasel300 View Post
I only use vise-grip pliers on brake line fittings anymore. The metal is somewhat soft and the corrosion layer is enough to round the fitting off with normal force. I've not met a fitting yet that didn't come off with the vice-grips. The key is to support both sides of the fitting and get those vice-grips TIGHT.
How about some elaboration on that.
Are you speaking of a Vise-grips as in the attached pic or the one with 2 curved jaws, 2 flat jaws or one that has one flat jaw other jaw is a is a combination of a short flat area at the front and curved a bit in the back?

I don't own one but some members have use the one in attached picture on Brake lines and said it worked well.
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Rear Hard Brake Line Removal-vice-grips-special-2020.jpg  
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  #15  
Old 10-19-2020, 02:38 PM
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Quote:
Originally Posted by Diesel911 View Post
I don't own one but some members have use the one in attached picture on Brake lines and said it worked well.
I used that type of vicegrip when I had same problem as OP. They come in two sizes, I believe. Needed the small one. I am sure there is a thread here about those and even my travails! OK, here is one of my posts: http://www.peachparts.com/shopforum/3340948-post9.html

In the end, I replaced the lines on both sides with premade Cunifer (Cupro Nickel) lines. If I remember correctly, these lines connected to a tee at end of the long line from the front.

The cunifer lines had connectors at both ends and were available in several lengths. They are easily bent by hand. I seem to recall that one side is shorter than the other. I may have used two pieces on the longer side? Cant recall - OK here is the link: http://www.peachparts.com/shopforum/3342292-post16.html

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Last edited by Graham; 10-19-2020 at 02:49 PM.
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