How do I isolate the leak?

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Got it. I bench bled the MC. I checked everything out and nothing looks bad on the old MC. But its probably something I can't see with my untrained eyes. Anyways I am going to bleed the system later today and hope for some real stopping power!

What kind of silicone or locktite can I put on the brake lines before I screw them into the MC to prevent leaks and so forth? Should I use grease on those also?
 
The fittings at the m/c do not require anything,, just screw them in,, they have a flared end on the end of the pipe that seals on a brass seat in the m/c.... just tighten em up,...

if you get any fluid on the paint,, rinse it with water IMMEDIATELY.. and keep a cloth over the m/c fitting while bleeding,, too avoid any spray... cheers
 
Okay thanks. Just making sure. I was paranoid that I'd have a leak in the engine bay if I didn't put something on em.
 
Just finished the job. The Brales are still not giving me good power. The pedal is pretty stiff but the braking is very lacking. What did I do wrong? Or could It be something else?
 
Does the pedal stay 'stiff' when you hold your foot on it or does it bleed off?

You may need to adjust the rear drum brakes.

I believe you said a brake job was done, so your front disc pads should be good....

Of course since you have a booster if it's bad then the brakes will be hard to push.
 
The brake pedal is pretty stiff, but it might bleed off a tiny bit. Not much if any though. No visible leaks. Brake pads are good. I did not adjust the drums, but the discs are not doing their job. It seems to have a similar problem that it did before I started the MC replacement. I used a master cylinder from sumittracing that came up for my specifications. It looks identical to my old one except for in the inside of the MC chambers, one of the two holes is slightly smaller than the old one. Does that make sense?
 
What is the masters bore size? When you have the wheels off have someone step on the brakes and see it he caliper pistons move against the rotors.
 
1.031 in. Bore part number M75817 doorman master cylinder. I re bled the whole system including the MC again. The brakes work a little better now. Maybe at 65-70% braking. I think I was impatient and may have not gotten all the air out of the system. Still not perfect, but improvement none the less.
 
Okay. So I bench bled the master cylinder, bled the brakes, replaced the wheel cylinders on the rear drums, adjusted the drums, checked the front disc for low pads. After bleeding today the brakes felt better than they have during this whole process, however, the brake pedal still goes down almost to the floor. The car brakes, but not too well. If I pump it up it'll get a little firmer but won't stop much better. The brakes are working and they're working okay, but I know they're not working to their full potential. I've checked for leaks under the car and in all potential areas. No leaks.....maybe more air in the lines still?.. I'm running out of ideas. Please help!
 
The pedal shouldn't go almost to the floor. When people above say "stiff" they mean that the pedal doesn't move much when you push it from nothing to very hard. Your's sounds "spongy" or "springy". Since it doesn't continue sinking (at a constant applied force), your MC is fine. The main thing that would cause springiness is air in the lines. Explain exactly your bleeding procedure.

Before that, try backing up and stopping hard about 20 times. That will let the self-adjusters do their job on your rear drums, assuming you have them and installed them correctly. Whoever put new brake parts on my 64 Valiant reversed L & R parts so the adjusters would try to loosen the shoes each time you stopped.

"If I pump it up it'll get a little firmer". I don't understand this. The MC is not like a hydraulic pump (which has a check valve). It doesn't give you more pressure when you pump it multiple times. The only time that multiple pumps helps is if your pedal is slowly sinking to the floor, and you told us it isn't. Do some more tests and carefully note and describe the results.
 
Sorry bad explanation. I guess a more accurate description is that the pedal is "springy". I can drive around my neighborhood and it'll stop if I push the pedal to the floor, however, I need to use a lot more muscle to get it to work. Plenty of brake fluid in the mc no leaks.

I don't quoted understand why I should back up and slam in the brakes...? What will this do? I'll do it I just want to understand what I'm doing.

I bled the brakes with the brake bleeder kit that creates pressure on the mc and you can open up the bleeder valves with one person. I bled the rear passenger drum them the rear drivers then the front pass her and the. The front drivers side. I opened up the valve and watched for bubbles and when it was clear I closed it and moved to the next one.

Thanks.
 
Did you try checking for air, as I described,, could save a lot of yakkin, and save you from chasing your tail, - and once eliminated, would help us, - help you.. ??

"to check for air after,.. with m/c cap on,, have friend pump 2 or 3 times and hold down,,, remove the cap,, have pedal released as you watch fluid levels,... any "geyser" ( fluid spouting well above the surface) is compressed air, "springing" back,, front or rear,, -- -

-with the exception that,- if the rear brakes are outta adjustment,, the return springs can cause a small fluid return from the rears.. "

- this can be resolved by setting the emergency brake..

For over 30 yrs. been checking that way, works in my shop..
 
inertia said:
"to check for air after,.. with m/c cap on,, have friend pump 2 or 3 times and hold down,,, remove the cap,, have pedal released as you watch fluid levels,... any "geyser" ( fluid spouting well above the surface) is compressed air, "springing" back,, front or rear,, -- -


For over 30 yrs. been checking that way, works in my shop..
Click to expand...

Nice tip!
 
firefighter1 said:
I don't quoted understand why I should back up and slam in the brakes...?
Click to expand...

If you have self-adjusting cables on your rear drums (1971 should), they adjust when you brake in reverse. You don't have to slam them on, just stop firmly. The more times, the better. I had too much pedal travel in my 65 Dart after a brake rebuild (drums F & R), which went away after above.
 
Have you pulled the drums and inspected the rear brakes? Here is a list of things to look for:
1. Stuck wheel cylinders. This happens when corrosion locks the pistons in the bores. Wheel cylinders are about $10 each and change easily unless brake line fitting is rusty.
2. Brake lining detached from brake shoe. Replace
3. Adjuster cable rusted, stretched, or broken. Replace.
4. Adjuster locked with rust. Spinning the star wheel is not possible. Replace.
5. Brakes are not adjusted and centered, such that there is just a bit of friction as wheel is rotated. Adjustments are made by pulling the rubber plug and rotating the star wheel to move the shoes out. Press brake to center, adjust ... If too tight it is difficult to go the other way, since self adjuster stops the star wheel.
6. Consult manual. Check if shoes are in incorrect locations. Check the springs, star wheel, and self adjuster are correctly installed. Things are similar front to back, but vary from side to side. Someone may have been in there before you and made mistakes.
 
Thanks for the tips guys. A lot of useful help. To answer you question yes I did check the drums. I said in an earlier post that I adjusted the drums and replaced the wheel cylinders already. I inspected them and everything looks good. Good shoes good springs nothing rusted except for the wheel cylinders that I replaced on both sides just for the hell of it. I will check for air in the lines today as I am off. Also I will do the backup and brake experiment to see if it improves the drum braking ability. Thank again!
 
Same old problem guys. The one thin I haven't done yet is check the front disc calipers to see if they've gone bad. How can I check the calipers?
 
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