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How to remove frozen brake lines, what I learned

I knew I needed new brake hoses when I tried to bleed my brakes and could not get any fluid to come out of the wheel cylinders because of the 40 year old swollen rubber lines. I knew my front hoses were replaced about 20 years ago because of the 9/94 date on them so I decided to replaced them for good measure.

I started with the front drivers side. After soaking the fittings with PB Blaster for a couple of weeks, I tried to remove the front hoses. The nuts on the line would not turn. I tried cleaning the outside of the lines, I tried heat, nothing seemed to work. I ended up rounding over the nuts with my flare nut wrench and had to cut them off with a Dremel, ruining the brake lines. Not fun but I was able to put new cunifer hard lines and braided hoses on the drivers side.

On to the passengers side. I really didn't want to have to cut the nuts off and replace the line that ran from the hose, along the firewall to the MC with the engine in the car. There had to be a better way. I remembered an article I had read about penetrating oil comparisons. PB Blaster, Liquid Wrench and Kroil were all good but a 50/50 mixture of ATF and acetone was much better. So I mixed some up and put that on everyday for about a week with a syringe and tube.


Trying to find a better way, I read online that the nut on the hard line is locking the hard line in place and the trick is to hold the nut still and turn the hose instead. I had to find a way to hold the nut without destroying it. Then I found a pair of small 4LW vise-grips specifically made to hold hex nuts. One jaw has a V that fits on two flats of the nut and the other jaw holds the opposing third flat. I was able to get a very good grip on the nut.


I found the vise-grip on Amazon and they are made for hex nuts 1/4 to 9/16.


Holding the vice-grip stationary, I had to exert extreme force to the 14mm wrench on the hose. With a loud snap. it broke loose with out damaging the line, nut or hose. I was then able to do the same for the other three nuts and remove the hoses.


New stainless steel braided hoses


The bleed nipple on top of the right caliper was also frozen and had been rounded in an effort to open it. A six point socket was not going to work. I needed to use a different vice-grip with teeth to lock down on the bleeder. I did not want to crush the bleeder and break it off so I put a 1/8" drill bit in the bleeder for strength.


With the bit out and my eye protection on and a fire extinguisher near by, I heated the bleeder red hot. Propane was not hot enough so I switched to Mapp gas which got the bleeder nice and red. BTW, I put my hand on the caliper and it was barely hot.


I tapped the bleeder with a hammer and then quenched it with a wet rag. I dropped the bit back in and then was able to unscrew it with the vice-grips.



Replaced with a new nipple, job done.


When I did the back hoses I soaked them with PB Blaster for about a week. I unbolted the center brackets for the sway bar and let it hang for room to turn the wrench. Once the 14mm wrench is on the hose, there is no room to turn it so I had to turn the nut on the line. For the other end of the hose, I put the 14mm wrench inside the trailing arm on the hose and then loosened the nut. Tight working space but I did not need to cut the hose to remove. I was able to remove the rear hoses by using my flare nut wrench. I think the fact they had 40 years of oily grime protecting them, they did not fuse together.


The beauty of the small 4LW vice-grips is that it has no teeth to mar the nut. The flat jaws hold three opposing flats of the nut putting equal pressure inward and will not deform the nut. Here is a picture holding an M6 nut that takes a 10mm wrench.


But the real trick to removing the nut is to hold it stationary with the hard line and turn the hose to break it loose. Once loose, I was able to used a flare wrench to remove the nut.

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Great article with great photos. The tips about removing the brake hoses I'm sure will be invaluable  I bought the 4 inch (4LW) and the larger 8 inch model.

Used the 4 inch today to do a complete brake job and found it sooo useful to crack the 11 mm brake lines from the wheel cylinders, the calipers and the master cylinder  No fear of rounding the nuts -- what a tool  !!

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Thank you. Another trick I read, and used, about the back brake lines - cut the line and use a deep well socket on the side you can't reach. Then you can easily unbolt it. Putting it back on is a lot easier of course because it is the new line. 

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Great tip for the vise grips, if you do that in conjunction with the tip above you should avoid needing to replace any hard lines because you've rounded off the ends or broken the lines. I did my rear brakes last week and ended up having to replace a couple of the hard lines because the ends were so hard to get to that I ended up rounding them off.


Thank you. Another trick I read, and used, about the back brake lines - cut the line and use a deep well socket on the side you can't reach. Then you can easily unbolt it. Putting it back on is a lot easier of course because it is the new line. 


+1, can I say +2? I came to the same conclusion, unfortunately it was after rounding off, breaking, swearing and beating. I kept meaning to post this tip on this thread. 

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I just went through this on my '79 635CSi with 220k on it. Every one of the rubber lines had a death grip on the metal lines. Even using the correct flare nut wrenches, I rounded the first two off.  What made the difference was heating each joint with a MAPP gas torch. I cut up some disposable aluminum roasting pans to try and protect the undercoating, but some of it got toasty. But getting each joint red hot, then soaking it in Silikriol to draw it into the threads, made me get the rest of them off without rounding.

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A professional mechanic loaned me a Snap-on hose wrench, said it was the only brand that would not round off the corners on brake line nuts. It would be interesting to confirm this, FWIW, it worked at the time I used it. Having used Crapsman and rounded off nuts, I'm biased.

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