Air in brakes

[Markham]

Paul,

I have a close friend that has been having problems with air in the braking system on a 1976 and a pedal that goes to the floor over time. The calipers are all new and no leaking at the calipers.

Can the Master Cylinder cause an intrusion of air into the lines?

We have bleed in the proper order and several inches of air (air in the fluid when exiting from the bleeder through a clear hose) come out after a few runs around town. The air is mostly in the fronts.

I thought that the master is a closed system with fluid and cannot see how air would be entering this way without fluid leaking out somewhere.

Thanks in advance.

Mark

[c4c5specialist]

HI there,
It may be the master cylinder.
But, the truth is that if there is air in the master cylinder, it will change if you pump the pedal 10 times. This will compress the air and make the pedal harder.
If not, air is getting in somewhere at the master cylinder.
BUT, it would be suggested to flush all the fluid through, maybe a full pint, just to be sure.
Allthebest, c4c5

[bradfordsvettes]

Originally Posted by c4c5specialist

HI there,
It may be the master cylinder.
But, the truth is that if there is air in the master cylinder, it will change if you pump the pedal 10 times. This will compress the air and make the pedal harder.
If not, air is getting in somewhere at the master cylinder.
BUT, it would be suggested to flush all the fluid through, maybe a full pint, just to be sure.
Allthebest, c4c5

also check the run out of the rotors although the problem is usually seen in the rear rotors, if the run out is to high the calipers pistons can pump air into the system by moving the pistons back and forth. very common on the rear these C3 cars so 2 places to look at to start Steve

[Markham]

We will take all the suggestions.

I will respond back with the results soon.

[Markham]

We put in the new Master Cylinder. The old one was leaking out the back.

Once we bled the brakes (which took quite a few pumps (14 or so) to completely get out all the air) the system seems to be pretty good. The pedal seems a little spongy to me, but he is happy.

Can the leaking Master Cylinder cause damage to the Booster?

Mark