The Stovebolt Site Forums The Shop Area Driveline New master cylinder pedal will not move

Hey,

I just replaced the front and rear brakes with disc brakes and ran all new brake line on my 54 3100. I also replaced the mater cylinder with a dual master and proportioning valve. The pedal was able to be pushed to the floor fine yesterday but I did not have help to bleed it so I pumped it a couple times just to make sure it worked. So today I tried a vacuum bleeder starting with the farthest away in the rear and I tried fora good deal of time. After no fluid I asked came out I asked my son to help by pumping the brakes. He got in and the pedal will only move maybe 1/2” at most.

I have bench bled the master before installing as well. I disconnected all brake line from the master and had my son push the pedal again and again at best it will move 1/2” and a small amount of fluid will come out of the front and rear ports on the master.

I tried tapping on the master as suggested on a google search about condition no pedal and that has not worked. Any help at all would be greatly appreciated.

If the pedal doesn't move it seems clear that fluid is not able to move out of the master cylinder. I would start at the master cylinder connections and loosen one at a time to determine if the problem is internal to the master or downstream, e.g. proportioning valve.

Thank you for the advice. I forgot to mention I did that and I tiny bit of fluid does come out. It appears to be internal to the master cylinder. Not sure like and air or vacuum lock. Can’t image it just broke but maybe. And thoughts on seeing if it is air locked somehow?

Not sure if this could cause your symptoms...
Check the pedal and linkage to make sure the piston is returning all the way when your foot is off the pedal. If there is a booster, you need to check the rod between the master and the booster.

There should be a bit of free play in the actuating rod. Maybe a 1/16” or a little more.

I doubt that it is air as air is compressable and the pedal would continue to move.

As Gord said it could be linkage, something dropped out of place preventing the piston in the master from actually moving, perhaps when you pumped it back on day 1.

Tha fluid drippling out of the master posts when you loosened fittings at the master would indicate that there is a fluid path on the outlet side so seems likely that the master piston is not moving for some reason.

Thank you everyone for you help. It ended up being the rod from the pedal to the master cylinder getting bound up at the pedal. I have resolved the issue and now on to try to get the air out of the system. Not luck yet but I am sure it will get out eventually.

Some of us have had great luck with Motive pressure bleed system, I have a GM dual (split)master cyl in my 46, worked very well, and 1 person bleeding. Used c clamps instead of chains….
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