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Old 06-22-2017, 10:51 AM   #1
Droff
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Brake line connection

I have found a brake fluid leak on the rear driver's side brake line of my '68 GMC 3/4 ton. It's leaking at the spot where the tubing comes through the flare nut, can't get it to stop. I had a plan to remove this line and either replace it or re-flare the current line. It's a new wheel cylinder.

There's a tee block on the rear axle that feeds each side of the truck and I can't get the line to break loose of this tee. It's been sprayed with PB Blaster for a few days but no luck yet. It feels like with more torque on the nut, everything will twist up into a nice little piece of scrap metal. I've got a wrench on the flare nut on the pax side to help with this but neither side will move.

Anything I can try in order to get this broke loose? It isn't rusted.
Thanks.
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Old 06-22-2017, 11:14 AM   #2
B. W.
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Re: Brake line connection

The line is probably cracked right at the nut, that's why it won't stop.

If all else fails, remove the tee completely. This may involve replacing both hard lines & the hose, if the lines & hose are old it's a good idea to replace them anyway.

Place tee in vice & use light heat (whatever that means!)
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Old 06-22-2017, 01:10 PM   #3
GASoline71
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Re: Brake line connection

If it comes down to it, a new set of pre-bent mild steel rear brake lines from Inline Tube will be fairly cheap. The rubber line with a T is also available from them. But you can also find that line at almost any auto parts store.

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Old 06-22-2017, 02:57 PM   #4
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Re: Brake line connection

I have had to use a "little" heat on some brake line fitting to get them to brake loose.
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Old 06-22-2017, 04:23 PM   #5
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Re: Brake line connection

Quote:
Originally Posted by B. W. View Post
The line is probably cracked right at the nut, that's why it won't stop.

If all else fails, remove the tee completely. This may involve replacing both hard lines & the hose, if the lines & hose are old it's a good idea to replace them anyway.

Place tee in vice & use light heat (whatever that means!)
Cheap and simple enough...
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Old 06-23-2017, 08:30 AM   #6
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Re: Brake line connection

Quote:
Originally Posted by B. W. View Post
The line is probably cracked right at the nut, that's why it won't stop.

If all else fails, remove the tee completely. This may involve replacing both hard lines & the hose, if the lines & hose are old it's a good idea to replace them anyway.

Place tee in vice & use light heat (whatever that means!)

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Originally Posted by demian5 View Post
Cheap and simple enough...
I'd have to agree.
I haven't tried disconnecting the rubber hose yet but replacing the lines may be the easiest route to take. Not sure on their age but the cost kinds of makes that a non-issue.
Thanks.
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Old 06-23-2017, 09:25 AM   #7
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Re: Brake line connection

Also agree. Best route is to replace everything. Brake lines have a way of blowing at the weakest spot, and always when you need them most.

As for bleeding. Consider a set of Russell speed bleeders. Makes the process an easy one person job. $20 for set of 4 is money well spent in my opinion.

[edit]
Another thing. Annealing the flare ends with a torch works well for eliminating work hardening in the metal from the production process. You will find the flares conform & seat much more easily.
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Last edited by GRX; 06-23-2017 at 09:35 AM.
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Old 06-23-2017, 09:36 AM   #8
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Re: Brake line connection

GRX... since you mentioned it. Can stainless steel be annealed?

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My 1972 GMC 1500 Super Custom (Creeping Death) "long term" build thread.

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Quote:
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I love using vacuum gauges as part of the carb tuning process. I hook the gauge to the inside of my garbage can and leave it there.
Quote:
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Remember Murphys 2nd law of mechanical relationships... "OPPOSING COMPONENTS ATTEMPTING TO OCCUPY THE SAME SPACE, AT THE SAME TIME, GENERALLY END UP OCCUPYING ADJOINING SPACE AT THE BOTTOM OF THE OIL PAN"
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Old 06-24-2017, 09:14 AM   #9
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Re: Brake line connection

Yes. Most brake line is made from grade 304 (A2) stainless which can be work hardened & annealed. Best method would be heat to dark cherry red then quench in cold water. Grade 304 is by far the most widely used since it has good form-ability and corrosion resistance. Typical for everything from sinks to bolts to eating utensils.
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Old 06-24-2017, 10:28 AM   #10
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Re: Brake line connection

You're already getting into the system and need to bleed it, so getting new lines is great insurance. Also, if you haven't replaced the rubber rear hose, it's probably a good time to get at that as well.
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Old 06-24-2017, 11:01 AM   #11
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Re: Brake line connection


Just be glad they don't make the lines from 316 ss.

Just be sure if anyone uses ss lines to use antiseize on the threads.
Also lapping the line nuts tight is a good idea for a leak free joint useing double flares. Just be extra careful on those brass fittings.
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Old 08-11-2017, 02:39 PM   #12
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Re: Brake line connection

It's been a while but I did change out the rear line as well as the rubber hose on the rear of the truck. I ordered from Inline Tube and used the old tee after I got everything cleaned up.

I had more than one leak when I put everything back together and thought I got them stopped but it doesn't appear that way. It looks like the tee connections are good, not any leaks or seepage from there, but fluid is seeping at both wheel cylinders. It's not much of a leak but if I put a towel up against the connection, it draws fluid away from it. I noticed while trying to bleed the lines.

I stopped working on it a couple weeks ago for other projects but everything was tight and both reservoirs were full of fluid.

I checked the reservoir last night and the rear is dry, all the fluid is gone, but nothing showing up on the ground. I traced the rear lines and haven't found any areas that appear to have a leaking problem.

This has been an area of frustration to say the least.

I have drum/drum brakes and a two reservoir MC, but the brakes go to the floor like the fronts aren't doing anything. They've previously been bled and the res level hasn't dropped or run dry, why wouldn't I have some kind of pedal? I do have a distro block.

I'm going to try and get under it over the weekend, just not sure what to look for or what to do to stop the leakage at this point (other than the obvious, re-tighten all the connections).
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Old 08-12-2017, 12:09 AM   #13
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Re: Brake line connection

It sounds as if you also have a master cylinder issue. The fluid from the rear reservoir may have leaked into the brake booster. The lack of any pedal would indicate air in the system or the seals in both the front and rear are bad and leaking past internally. You said you replaced the wheel cylinder. For what reason? Did you tear it down, clean and inspect the bore? If not I would take the time to do it. If the bore is rusted and pitted then it is likely the other brake components are in similar condition. As far as your seeping at the wheel cylinder. Did you use anti-seize on the threads and the back of the flare when you assembled the lines. Assuming you went with the stainless tubing.
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Old 08-12-2017, 11:15 AM   #14
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Re: Brake line connection

This why I am a big advocate for annealing the flared end before assembly. Test fitting parts before hand helps too. Tighten the cylinder on end of tubing, loosen slightly, spin the cylinder around, tighten, repeat. In this way you ensure the two conical surfaces are well married before installing on the vehicle.
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Old 08-12-2017, 07:55 PM   #15
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Re: Brake line connection

Thanks for the input(s).

The fluid was like black coffee, there were indications of a leak so I replaced the wheel cylinders due to unknown age and to get a known starting point. I don't have a booster, manual drum brakes all around.
I didn't use anti-seize on any of the connections and I used the OE replacement tubes.

So add anti-seize on the threads and where the tube goes through the fitting? Any recommendation on which anti-seize? I'm going to need to go pick some up if using it.

As far as annealing, I'm not quite sure what that entails but I did tighten, loosen, tighten 3-4 times on each side. The new wheel cylinders were already installed, and have been for some time.
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Old 09-04-2017, 01:48 PM   #16
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Re: Brake line connection

Well I got back around to looking at my brake issue yesterday. I disconnected the rear lines and then pulled both wheel cylinders out. I spun them on/off a few times to get a good fit between them, then re-installed everything again and bled the system. I wasn't getting any air that I could see when bleeding and the connections were holding up, they weren't leaking/seeping any fluid. I think re-mating everything helped the problem but the pedal still feels too soft..

I let it sit overnight to see if I would lose any fluid, the MC looks like maybe a little bit leaked off - somewhere. I also thought about the MC being bad so today I crawled in under the steering wheel and DOH! I'm losing fluid inside the truck, from the MC. (Sorry about the pic rotation, I tried to get it rotated..)

Now, rebuild this one or buy one? That is what I'm unsure of. I plan on putting power disc brakes on the truck, sometime down the road but time frame is not known. I don't know how well a rebuild will turn out, never rebuilt an MC but I don't want to drop more money than I need to since I'll be replacing it down the road anyway.

Looking for some input, rebuild or buy a new one? It's a 'drive to work truck', that's about it.

Thanks.
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Old 09-04-2017, 04:01 PM   #17
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Re: Brake line connection

Rebuilding it isn't very hard, the bigger issue is the bore rusted? You will need to remove the master cylinder from the fire wall to determine which bore size your truck has, so you can tear the master cylinder apart to determine if it is rusted inside at the same time. If it is rusted then go with a replacement master cylinder. If you go with a reman master cylinder I would buy local as it makes returning it easier. My personal record is only 30-40 percent of reman master cylinders actually work as expected.
Sometimes there is only a 5-10 dollar difference in price between a rebuild kit and a reman cylinder.
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Old 09-05-2017, 07:57 PM   #18
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Re: Brake line connection

Got the MC pulled, it could look better but I'm sure there are worse. I'm not familiar with these all that much and not having a lot of luck with a parts description.

Which is considered the bore size, the actual hole or the larger diameter piece inside the MC?

The smaller hole is 1/2" and the larger diameter piece is 1-1/8". I'm thinking this is the bore. From everything I've read, a drum/drum MC should be 1" at the largest or am I confused?

I'm leaning toward a rebuilt MC rather than buying a kit.

Thanks.
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Old 09-05-2017, 08:17 PM   #19
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Re: Brake line connection

The larger 1 1/8" is the bore size. I believe that 1 1/8" is the 3/4 ton manual brake bore size. You can double check me on that just to be sure.
There should be a snap ring holding the internal parts in if you want to go that far. As crusty as it looks it may take some work to get the guts out of the bore.
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Old 09-05-2017, 08:24 PM   #20
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Re: Brake line connection

http://www.classicparts.com/1967-70-.../#.Wa8_-7KGPIU

New...not rebuilt...$ 70....
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Old 09-06-2017, 08:48 AM   #21
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Re: Brake line connection

I saw the snap ring and was able to get it to spin around but how does that thing come off? There aren't any "O"s on the ends of the ring to put a pair of pliers in to. I can get a better pic of it later if needed to help explain that.

Thanks for the link Aussie, $70 isn't too painful.

Anyone have a source for the rubber parts that are on the shaft that goes through the firewall? Both of these have seen better days.
Thanks.
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Old 09-06-2017, 12:41 PM   #22
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Re: Brake line connection

If the ends of the snap ring are corroded away, I wouldnt waste any time on it...go new and save your frustration...

The boot on end of master cylinder is available from several suppliers..

try LMCTRUCK and

use part number 30-1914 Boot -Brake Pedal Pushrod..; $ 6.95

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