Rusted flare nut in brake cylinder

Tiny
ITISME201411
  • MEMBER
  • 1995 GMC SIERRA
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 150,000 MILES
I was changing a leaking driver side rear brake cylinder and I am not able to get the flare nut out of the cylinder. It is rusted out an I tried allot of penetrating fluid an heat. Using vice grips an a line wrench. What do you suggest? Change that part of the line?Thanks.
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Saturday, April 15th, 2017 AT 6:50 PM

13 Replies

Tiny
CARADIODOC
  • EXPERT
This will actually be pretty easy, but I am not going to tell you how I would handle this until you promise me you will wash off all the penetrating oil with brake parts cleaner. Using that is the number one way this can turn into a real expensive repair that could exceed the value of the truck.

If any hint of petroleum product makes it into the brake fluid, the entire hydraulic system will become contaminated, and that will soften and destroy all the rubber parts that contact the brake fluid. The only proper repair for that is to remove every part that contains rubber that contacts the brake fluid, flush and dry the steel lines, then install all new rubber parts. That includes wheel cylinders, calipers, master cylinder, three or four rubber flex hoses, combination valve assembly, bladder seal under the reservoir cap, and if used, the height-sensing proportioning valve. Those are usually found on pickup trucks and minivans. If you have anti-lock brakes, the four-wheel hydraulic controller must be replaced. If you have rear-wheel ABS, the dump valve assembly must be replaced. If any rubber part is overlooked, the contamination will leach out of it and recontaminate the new brake fluid.

Most brake system specialists will not even allow things like power steering fluid, engine oil, transmission fluid, or axle grease near their jobs. We even wash our hands before handling the seals for caliper and wheel cylinder rebuild kits to prevent getting fingerprint grease on them.

Now that you have been properly warned, do not even waste your valuable time trying to solve the nut problem. Even if you do get it loose in the wheel cylinder, it will be rusted to the line, and the line will twist off. Do you really want to reinstall that nut? Cut the line right next to the wheel cylinder only if that is necessary to get the wheel cylinder off. Cut the line on its other end where it most likely is attached to the brass block at the end of the rubber flex hose. That will be on top of or next to the rear axle's center section. Cut that line real close, because the next step is to pound on a six-point socket. Line nuts are very soft. They will deform easily to allow the socket to be driven on. If all you have is a 12-point socket, stop right there and find a 6-point. No sense making more frustration for yourself. Even if the truck is real rusty, this nut will come loose very easily because it is screwed into brass.

Replace the entire line, along with the new wheel cylinder. Pre-manufactured lines are very inexpensive. Get one that is only slightly longer than it has to be, then put some gentle bends in it to take up the extra length. Avoid bending in a high spot where air can be trapped.

Here are some tidbits of wisdom I have acquired over the years. You are going to add a lot of misery to the job if you let the brake fluid reservoir run empty, especially if you have four-wheel anti-lock brakes. To prevent that, place a stick between the seat cushion and the brake pedal to hold the pedal down about two inches. Gravity will not be strong enough to pull the brake fluid past the rubber lip seals in the master cylinder.

Once the new line and wheel cylinder are installed, remove the stick, and loosen the cover on the reservoir. Open the bleeder screw on the wheel cylinder, then wait for brake fluid to show up. Do not push the brake pedal unless the fluid does not start flowing on its own. With such a short new line, gravity-bleeding should only take no more than a minute. Once you see fluid flowing and there's no air bubbles, close the bleeder screw, then "irritate" the brake pedal by hand, just enough to turn on the brake lights a couple of times. That will wash any sticking air bubbles into the wheel cylinder. Open the bleeder screw once more just long enough to burp out those couple of bubbles.

If you ever think it is necessary to resort to pedal-bleeding with a helper, do not ever push the brake pedal over half way to the floor. Crud and corrosion build up in the lower halves of the bores in the master cylinder where the pistons do not normally travel. Running the pedal to the floor runs the rubber lip seals over that crud and can rip them. That results in a slowly-sinking brake pedal, and that often does not show up until two or three days later.

As long as you are in there, check that the brake shoes come to rest against the large anchor pin at the top of the backing plate. Also, verify you can push the parking brake strut bar, between the middle of the two shoes, forward with your thumb, against the anti-rattle spring. That bar should move a good 1/8". If the bar is tight or the shoes are not fully retracted, a parking brake cable is sticking partially-applied.

This is also a good time to pull the shoes away from the backing plates just enough to look behind them to see if grooves have worn into the backing plate. This is a bigger problem on GM vehicles because the edge of the shoe frames grind those grooves. Other manufacturers bend over little tabs on their shoe frames to spread out the contact area and reduce the tendency for those grooves to form. Once those grooves become bad enough, a shoe can fail to apply under light pedal pressure, and in extreme cases can fail to release after normal to hard braking.

Do not get any grease or brake fluid on the friction surfaces of the shoe linings or drums. If you do, that can be washed off with brake parts cleaner, but it must be done before those parts become hot from braking. If that contamination is there when the parts become hot, it will soak into the linings and into the cast iron, which is porous, and never come out. That will cause an irritating brake squeal.
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Saturday, April 15th, 2017 AT 8:28 PM
Tiny
CARADIODOC
  • EXPERT
Thank you for including the photos. I overlooked them the first time. You can see the line right next to the nut is badly rusted and is going to break. There is absolutely no way the nut will ever spin on that line again without leaking. The only thing you could hope to do is get the nut loose, then rotate the wheel cylinder to unscrew it from the nut. Most of the time you have to twist the cylinder as you rotate it, and that too will crack the rusty line. Just throw on the new line and wheel cylinder, then buzz off into the sunset.

For one more comment of great value, pop off one of the dust boots from the old wheel cylinder, then let one of the pistons and lip seals spring out. Look on the inside of the lip seal and you will see the diameter is molded on to it. Read that and verify the new wheel cylinder you bought is the same diameter. The diameter is carefully selected at the factory to provide balanced braking, front-to-rear, for the truck's weight and weight distribution during braking. Common diameters are 13/16", 7/8", and 15/16". Be sure you are installing the same size that you removed.
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Saturday, April 15th, 2017 AT 8:42 PM
Tiny
ITISME201411
  • MEMBER
Thank you. I pretty much figured I was going to be replacing the line. Anytime I do anything with brakes I make sure they are clean. I do it all on my own. So any input on anything automotive I greatly appreciate.
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Saturday, April 15th, 2017 AT 9:14 PM
Tiny
ITISME201411
  • MEMBER
So I replaced the cylinder an brake line. Now my issue is that the brake line leaks just a little not allot were it goes through the nut that is screwed into the cylinder. Ive put 3 different lines an all 3 do that. Any suggestion on why?I snug down not overly tighten so not sure.
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Wednesday, May 3rd, 2017 AT 9:21 AM
Tiny
CARADIODOC
  • EXPERT
One potential problem occurs when you make your own double flare on a piece of bulk brake line. The final step is to push the end down to form the double flare. If you smash it down real tight, there will be no give to it to shape itself to the wheel cylinder. You may not be able to get the nut tight enough to make the flare seal. That is not a concern with pre-manufactured steel line, and with three lines, certainly one of them would have sealed.

There are other leaking problems related to making your own flares. One is the flare cracks, which can't be sealed against leaking. Another is when the bulk line is cut to length, the inside has to be reamed out to taper the inside edge a little. Failure to do that can leave a sharp point, or tab, that can get stuck on the end. That tab can break off and become stuck in the wheel cylinder's port where it will hold the flare from seating fully. Find that with a magnifying glass and flashlight, or wash the port out with brake parts cleaner.

For the most likely suspect, look at your old flare that you removed, and compare it to the flare on the new line. My guess is you're going to find you installed a line with a double flare, and the old one was an "iso" flare. That type of flare looks like a double flare that didn't have the final forming step performed. I don't know how the threads on the nuts compare, but there are a few different thread pitches, so one incorrect line might bolt on, but not seal.
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Wednesday, May 3rd, 2017 AT 12:09 PM
Tiny
ITISME201411
  • MEMBER
The lines came flared already I did not have to.I have to cut the old ones they were to rusty an would not come out of the old cylinder.
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Wednesday, May 3rd, 2017 AT 12:26 PM
Tiny
KEN
  • ADMIN
Good to hear, please use 2CarPros anytime we are here to help.

Cheers, Ken
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Wednesday, May 3rd, 2017 AT 12:36 PM
Tiny
CARADIODOC
  • EXPERT
I know you used pre-made lines. I just included that information to show how smart I are!

What you should do is compare the flare on the new lines you're trying to use to the old flare you, ... Oh, wait. I overlooked the fact you couldn't get the old flare out to look at it.

I tried to look at some photos of your wheel cylinder, for reference. One looks like it has a double-flare port, one looks like an iso-flare, and one I can't tell. You might want to return to the parts store and have them pull another wheel cylinder and look at the port, then compare it to the standard line with a double-flare and see if it matches.
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Wednesday, May 3rd, 2017 AT 1:05 PM
Tiny
ITISME201411
  • MEMBER
I got the brake line issue fixed now I am on the parking brake issue. So I ran the cable but on the drivers side were they connect the cable is a little short but the auto store says it's the right one. Not sure how it could be. Unless I am doing something wrong?Here is a pic.I tried pulling it an it goes no further.
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Saturday, May 6th, 2017 AT 1:48 PM
Tiny
CARADIODOC
  • EXPERT
What solved the leaking line?

I believe the connector is on the cable that goes to the front main cable. Sometimes there's a hook hanging from the frame or cross member to hold the cable, and there are multiple holes in the frame. Check if there is a different hole that hook can be moved to.

If you replaced the rear cable(s), be sure the casings are snapped into their fully-seated positions.

The most common thing I run into when the cable is too short is the parking brake pedal dropped down and is in the partially-applied position. Have a helper pull the release handle, then tug on the cable. I bet that will get you the few extra inches you need.
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Saturday, May 6th, 2017 AT 7:53 PM
Tiny
ITISME201411
  • MEMBER
I do have them them on the hangers an through the hole. Ok I will try that. Thanks!An the brake line I unscrewed off the the cylinder pulled it out an checked the flare to make sure it was a double then I put it back in the cylinder but I wiggled it a little bit an held it firmly an tightened it. So maybe it wasn't seated in the cylinder correctly?
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Sunday, May 7th, 2017 AT 6:30 AM
Tiny
ITISME201411
  • MEMBER
Well I tried having someone pull the release handle an I tugged but the cable didn't move. Do you think I should replace that?Possibly bad?
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Tuesday, May 9th, 2017 AT 11:51 AM
Tiny
CARADIODOC
  • EXPERT
Have your helper hold the release handle up, then pump the parking brake pedal up and down while you pull back on the cable. You should observe the cable going in and out easily. If it does not, it is rusted in the applied position. Do not try to fix it or lubricate for that as it WILL act up again at the most inopportune time. The only proper repair for a rusted cable is to replace it.
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Tuesday, May 9th, 2017 AT 2:13 PM

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