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Old 06-10-2006, 10:18 AM
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testing of new brake lines before putting car back together

Short of putting the car completely together (body off frame right now), does anyone have a good way to test the brake lines and finttings to know if it is leaking or not? I thought about capping the ends and then putting an air pressure gage on the lines along with a shut off valve and pressurizing to 100psi, if no pressure decay, then I am good.....other ways people have done it? If I have a leak, will be a heck of a lot easier to get to now than later

I should have also said that I was bending my own brake lines and flairing the ends myself. I am using 37 degree flairs and regular steel tubing.

thanks, Herb

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Old 06-10-2006, 10:23 PM
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Testing to a 100 psi doesn't seem like it will tell you much. Brake line pressures will easily exceed that even under light braking.

I did practically the same as you did when I replumbed the brakes on my T. The master cylinder was mounted to the frame and so was the brake pedal pivot. I used steel tubing which I bent with AN fittings. I found that the areas where I had pipe thread joints (residual pressure valves and proportional valve) leaked more than the flared fittings. In all cases, just torquing the fitting a little more stopped all leaks. Guess I didn't want to overstress the fittings when I initially assembled them.
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Old 06-10-2006, 10:56 PM
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my master cylinder and pivot are on the body which is off the frame. I realize that 100 psi air, isn't much, but air has virtually no viscosity, where the brake fluid must have at least 5 to 20 cP of viscosity, probably more. That is why I thought I could get away with 100 psi air. But that doesn't take into account any deflections that you might get with with 1000 psi hydraulic on the brakes.

I could pressurize the system with my lift hydraulics, not sure how many psi that will get me, but I bet it is at least several hundred if not more. Perhaps I will ask at work, there might be something there I could use, hmmmm, maybe one of our 32:1 paint pumps, just put solvent in the lines and pressurize it, if it leaks then I can take care of it, if there are no leaks then I am good, blow it out and will know that I have it all set.

won't want to have the brake hoses hooked up, I am not worried about them leaking, it is the rest of the system I am worried about, my flarings and to a lesser extent the pipe fittings part of the system.

you have given me some good things to think about.....perhaps a paint pump loaded with accetone will do the trick, will certainly blow out cleanly.

anyone else have any thoughts?

Herb
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Old 06-11-2006, 08:13 AM
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Quote:
Originally Posted by firstgear
I am using 37 degree flairs and regular steel tubing.

thanks, Herb
Steel brake lines should be 45 degree DOUBLE flared. 37 degree single flare is used for AN fittings only. Wrap any tapered pipe thread adapters with teflon tape to insure a good seal.
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Old 06-11-2006, 08:20 AM
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Quote:
Originally Posted by Frisco
Steel brake lines should be 45 degree DOUBLE flared. 37 degree single flare is used for AN fittings only. Wrap any tapered pipe thread adapters with teflon tape to insure a good seal.
I have all AN fittings....even the SS hoses have AN fittings, hence why I am using 37 degree flare.....
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Old 06-11-2006, 09:22 AM
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Quote:
Originally Posted by firstgear
.....perhaps a paint pump loaded with accetone will do the trick, will certainly blow out cleanly.


Herb
I'm not sure I would use acetone in a brake system. I don't know if the seals and valving, (your RPVs and proportioning valves have little rubber tube valves in them), will not get dried up by the acetone.
Denatured alcohol might be a better choice if you really feel
the need to pressurize it with a liquid .

If it were me I would only use air or brake fluid. I would not want to take the chance of any dissimilar liquids in my brake system. The air test at 100 psi will surely show you which of your flares are heinous leakers. If it doesn't leak at 100 psi then it will probably need no more than just a tighten up to stop any leaks when the system is fully installed.

Will your brake lines really become so inaccessible once the body is on that you can't check it out the normal way with the M/C and all the rest of the plumbing in? I would think that the effort you put into this test may be alot more than what it is worth.

BTW if you are using stainless steel tube with your AN fittings then 37* is the right flare.
If you are using the regular double wall mild steel tubing (bundyflex, eichmann), it needs to be double flared @ 45* and the correct adapters used to plumb into your AN stuff.. Mild steel tube doesn't hold up well single flared @ 37*. I have seen people use it and it work, but that doesn't make it right for a brake system.

Those are my thoughts on this,
mikey
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Old 06-25-2006, 12:12 AM
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sorry if this looks like Hi-jacking... but I'm also having trouble with manufacturing brake lines. Is there a photo example page somewhere that shows the different types of flairs and fittings? I'm on my second weekend and don't have any good results to show for my frustration.
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Old 06-25-2006, 12:58 AM
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Here is a page that has some of that info. http://www.fedhillusa.com/brakelinehelp.html
If you scroll down to the bottom (way down)you will see a button on the left that says PDF "brake line flare identification"
there is alot of useful info on that site if you browse around.
Hope this helps, mikey
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Old 06-25-2006, 01:13 AM
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Quote:
Originally Posted by powerrodsmike
Here is a page that has some of that info. http://www.fedhillusa.com/brakelinehelp.html
If you scroll down to the bottom (way down)you will see a button on the left that says PDF "brake line flare identification"
there is alot of useful info on that site if you browse around.
Hope this helps, mikey

Thank You Very Much Sir!
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