New Master Cylinder and can't get air out of one brake line

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Walker434

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first let me say that I don't have a ton of experience working on brakes so I may be doing something wrong. Working on a 71 Dart with manual drum brakes all the way around. Has new shoes, wheel cylinders, ect within the last year.

Recently realized my master cylinder was leaking so I purchased a new aluminum 15/16 master cylinder from Cass at Dr Diff. Didn't have a good way to bench bleed the new MC so I installed on the car and bled the MC on the car by cracking the lines and having wife pump brakes. Got all air out of MC and the rear brakes bled as expected. Had a very difficult time getting the air out of the front passenger side line but finally did. Now matter how many times I try I can't seem to get all the air out of the front drivers side.

I have made sure to keep the MC full of fluid while bleeding. Can't find any leaking lines. Any ideas? Wanted to see if I'm missing something before I call Cass and ask him. Thanks in advance for any help.
 
I had this same issue. Turns out, the new wheel cylinder was leaking. Pull back the rubber wheel cylinder cover that has the short rods that push out on the brakes. If there's fluid in there, in front of the inner rubber cup, that means the wheel cylinder is leaking. I ended up putting an old wheel cylinder back on. A lot of newer parts are junk. Also, you should have gotten a bleeder kit with your MC. Maybe the auto parts store sells them.
 
On particularly pain in the butt bleeds I use a squeeze bottle with a tube on it and force fluid from the wheel up instead of trying to force air down.
 
In the past, Ive just crack open the bleeder a bit, on the suspect line and let it gravity drip
making sure you keep fluid full on MC. Sometimes overnite. Always had improved results.
That is, if you dont have any tiny leaks.

D.
 
I had this same issue. Turns out, the new wheel cylinder was leaking. Pull back the rubber wheel cylinder cover that has the short rods that push out on the brakes. If there's fluid in there, in front of the inner rubber cup, that means the wheel cylinder is leaking. I ended up putting an old wheel cylinder back on. A lot of newer parts are junk. Also, you should have gotten a bleeder kit with your MC. Maybe the auto parts store sells them.
Thanks for the input I'll check under dash tonight to see if it's leaking
 
On particularly pain in the butt bleeds I use a squeeze bottle with a tube on it and force fluid from the wheel up instead of trying to force air down.
If I determine the MC isn't leaking I will either try this method or the gravity bleed method. Thanks
 
If I determine the MC isn't leaking I will either try this method or the gravity bleed method. Thanks

The problem with that is if there are air bubbles trying to go up and fluid trying to go down they can interfere with each other.
If it would gravity bleed, it would bleed through normal bleeding procedures.
That's my outlook on it anyway, but who knows when it actually comes down to it.
That's why I have multiple ways of bleeding depending on the circumstances.

The Ford Ranger with the hydraulic clutch was one that didn't like to bleed normally because the air would go up in the line while we were bleeding fluid going down.
It was WAY easier to push the air up than down.
 
In the past, Ive just crack open the bleeder a bit, on the suspect line and let it gravity drip
making sure you keep fluid full on MC. Sometimes overnite. Always had improved results.
That is, if you dont have any tiny leaks.

D.

Forgot to mention, keep MC cover off or loose. Air bubbles escape from both ends of system. Then do the routine bleeding process.
 
Just don't add up for me. The left front is the closest shortest tubing so should be the least amount of air and bleeding req'd.
Unless its sucking air in through a wheel cylinder or a flexible hose, I just don't know. If a hose is dry rotted, showing cracks, or damp/nasty where it shouldn't be, replace it.
 
Got an update. It was sucking air through a cracked bleeder screw. Replaced the bleeder screw and got all the air out. Took it for a drive and it stops well but the pedal seems to have more travel than before. Would that possibly because of the smaller 15/16 piston?
 
Got an update. It was sucking air through a cracked bleeder screw. Replaced the bleeder screw and got all the air out. Took it for a drive and it stops well but the pedal seems to have more travel than before. Would that possibly because of the smaller 15/16 piston?

Yep
 
Got an update. It was sucking air through a cracked bleeder screw. Replaced the bleeder screw and got all the air out. Took it for a drive and it stops well but the pedal seems to have more travel than before. Would that possibly because of the smaller 15/16 piston?
Unfortunately that happens more than it should, last time the store manager for one of the nat'l parts chains brought His '70's T/A for a set of rears & brakes, guess what
heppened & it was close to quittin' time!!! Pass. rear refused to stop burpin', yep.......................................................
 
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