1936 Buick Special Brake Job

[Guest KeithElwell]

I paid big bucks to have all my wheel cylinders and master cylinder sleeved by a well known reputable firm for my 1936 Buick Special Coupe. I looked them over carefully and they did a great job. Also got all new rebuild kits and assembled them carefully and cleanly. Also bought new steel brake lines and hoses and installed them. Got everything installed and tightened up pretty well. Then I bought me some DOT 5 Silicone brake fluid on the advice that a car that is not driven often and sits for periods of time will benefit from this type of fluid. The system was totally empty and clean so using the DOT 5 was not mixed with any other type of fluid. Then set about bleeding the brakes per my service manual.

Immediately after starting to fill up the lines, even before building up any pressure to speak of, I started having leaks. I went around everywhere and tightened up all the joints and resumed bleeding. To cut to the point, I bled the system the best I could but was never able to totally eliminate leakage. I don't know how I can tighten up these joints any more without rounding the shoulders over on the fittings. I am using flare wrenches where they will fit but in some spots against the brake backing plate there is no clearance so I have to use a crescent wrench tightened on the flats as much as possible.

Anybody have any advice for me?

I know I should not use teflon tape on the threads but I am tempted to try this.

I am tempted to try vice grips on the nuts and tighten them even further but this will destroy the flats and require vice grips to remove and really should not be required.

I could try disassembling the wheel cylinders again and see if I can do something to smooth up the cone shaped seal surface on the wheel cylinders that mates up to the double inverted flare of my brake lines.

Any other ideas?

[Pete Phillips]

Hey Keith,

It's a bit of a dumb question, but are the tips of the steel lines flared properly? Do the fittings have enough threads to bottom out properly in the joint? Where you can't use a flare wrench/line wrench due to brake backing plate in the way, get rid of that crescent wrench and just use a regular 3/8ths or 7/16ths open-ended wrench. It will do better than that crescent, and if you turn it slowly, you can tell when it is starting to round off the shoulders.

Another dumb question: You're certain that the angle of the fittings is correct and you aren't cross-threaded anywhere? I doubt if it could be cross-threaded in numerous locations, though, and you seem to have numerous leaks. If nothing works, send me an e-mail and I'll come over there next weekend to see if I can help.

P.S.: I have it on pretty good authority that there are going to be a couple of antique Buicks in the Greenville Christmas parade...! (not mine)

Pete Phillips

[Guest KeithElwell]

Thanks Pete.

I feel like I was being very careful not to crossthread anywhere. And I realize crescent wrenches are usually a bad idea period, probably never used by a true mechanic.

But I am taking off work for a couple of days so I will check out what you suggest tomorrow.

Wont be my Buick in the parade but the goal is for that same parade in 2013 with mine.

[danhar1960]

Wow, that doesn't sound good Keith. I don't think the DOT-5 fluid has anything to do with it. The flares should take up and seal with very little effort if everything is good. Maybe a couple of up-close pics if you can might be helpful to spot the problem.

Danny

[Steve_bigD]

Are you using stainless steel (SS) lines? It is much harder and requires almost a perfect fit to get a seal with SS lines. They will last virtually forever but due to the harder material are very hard to make a good leak free joint. Are the leaks at random joints or specific ones? I ask because there may be a slightly different flare angle on the original cylinders which could also cause problems getting a leak free joint. Did you make the flares yourself or buy the lines pre-flared? Perhaps your flaring tool or technique resulted in a slightly different flare angle.

I rebuilt my brake system exactly as you did with DOT5 silicone fluid (purple color) but went with rebuild kits and honing for the wheel and master cylinders. I used pre-flared standard steel lines and tightened the fittings with a standard flare wrench have had no leakage problems at all. That was 10 years ago and the DOT5 fluid is still crystal clear in the master cylinder. DOT5 was the correct choice.

Steve D

1938 40-41

[Guest KeithElwell]

I'm using new steel (not stainless) lines from an eBay vendor that already have the double inverted flares and tube nuts in place on each end. I did not form the flares. The lines looked ok but I'll admit that I did not carefully inspect each one before forming them. I went thru all the lines that came in the kit and picked the best length match between my original rusty lines and the new straight ones. Then formed them to fit each location. I wanted stainless but didn't spend the extra money.

Yeah the DOT-5 fluid should have nothing to do with my leakage problems. I just thought I would throw that topic out there for further discussion and debate on the forum. It's good to hear that at least one other person thinks it was a good idea and has seen good service from using this fluid.

Today I will be going back around and checking more closely for the leaks before opening up the system. I believe that all my leaks are between the wheel cylinder and the steel line. The rear brakes have the brass elbow fitting but the fronts don't need this extra fitting. So the rears may be leaking between this brass fitting and the steel line. It will be hard to tell exactly where the leak is. Anyway thanks for the input guys. I will keep at it.

[37_Roadmaster_C]

Keith,

No help or input on your problem other than what has already been said above. I did the same thing to my 37 Roadmaster that you are doing. I had the master and wheel cylinders rebuilt and sleeved and then replaced all of the lines, steel and rubber. I used metal lines from NAPA and flared the ends myself and rubber lines from Bobs and had no leaks or problems. I also used DOT5 fluid and have not had any problems. The rebuilder was very specific in letting me know that all parts that they used were compatable with the DOT5 fluid, same with the rubber hoses. I hope this eases your concerns about the fluid. Good luck and let us know what you find.

Robin

Edited December 6, 2012 by 37_Roadmaster_C
to add information (see edit history)

[Guest KeithElwell]

Working on this today I pumped the brakes some and checked all the connections. I had 3 spots that had a small seepage so I snugged these up a bit more and I find no more leaks there. However one spot remains a problem. This is the left rear brake. The problem seems to be between the brass "swivel elbow" and the new steel line. This is a difficult spot to see easily with old eyes. So it is possible that I have this brake line nut cross threaded into the elbow. I have a total of five of these brass elbows. One is the problem child at the left rear, one is installed successfully at the right rear brake, and three more are spares but one of these has part of the sidewall broken out at the threaded port for the brake line nut. I have found that none of my extra brake line nuts (not used for the car) will thread easily into my spare brass elbows. It appears to be matching threads but they just won't go together right. This must be the problem with the left rear. I have a leftover brass coupling to join two brake lines just like some that I used for my new lines, and the brake line nuts thread easily into this coupling. I will see if I can come up with another of these brass elbows on eBay or someplace (Pete?). I guess you guys know what I'm describing here but I may take a photo and post it.

[groselle]

Keith,

By brass elbows do you mean banjo fittings? I've attached a picture of one of mine below. I ended up cracking the fitting where the brake line goes into the brass body. I haven't been able to find a replacement yet. The good news is that a modern flexible hose will screw directly into the brake cylinder. There are also two copper washer that go on either side of the banjo bolt.

Greg

[39BuickEight]

On our car we had a couple of leaks. We just loosened and tightened the fitting several times and it eventually snug up just right and stopped leaking. I bet we did one 25 times.

[Guest KeithElwell]

Greg,

Yes, that's the part I was trying to describe. Now that you mention it, I have heard this part called a banjo fitting before.

It appears that this is my problem. The banjo fitting and center bolt seems to be in good shape but the female threads in this fitting for the brake line are some slightly different thread pitch or profile than the brake line nuts. I was apparently able to get the right rear one assembled in spite of this and for now it is not leaking. But the left won't seal up.

I think what I need to do is find two banjo fittings with the correct threads to match the brake line nuts. Or I can get about 12" long brake hoses for each side, going directly into the wheel cylinders like you suggest. Then a shorter brake line from these hoses toward the tee near the differential.

Billy,

Like you say, going back and tightening up the other connections seems to have done the trick there. But I won't really know if I've solve the problem till I fix the rears, bleed the system again, and pump it up for leaks.

[groselle]

Keith,

That's what I ended up doing on the left rear of my car. I've got a 12" flexible hose attached to a solid piece of brake line that goes to the tee on the differential. The mistake I originally made was getting the nut on the brake line cross threaded in the fitting and it was all down hill from there. I think the brass gets brittle with age too. If I were going to redo it I would thread the solid brake line onto the banjo fitting while everything was off the car. The I would attach the line at the tee on the differential at which point the brake line could be bent so as to get the banjo bolt in, then tighten it all down.

Greg