Brake Issue...

[smokem2024]

I recently took the brake booster off. I put a master cylinder straight to firewall and hooked up rod and lines. Sitting on stands we bled brakes and have a good pedal and they stop. When you set it down they don't stop unless you stand on pedal. This is not going to work. Is there a difference in master cylinders for power and manual brakes? I'm pretty sure the one I got was for manual brakes. It was for a 77 GMC truck and it came with the brake rod. Any help on this?

[smokem2024]

Ok since first post I changed master cylinder again. Realized I had one for power brakes. I got the right one for manual brakes and now the pedal is spongy. It stops better but just spongy. No where near where it supposed to be. Do you have to swap the lines around on the master? I have disc front and drum rear.

[95shaw]

Ok since first post I changed master cylinder again. Realized I had one for power brakes. I got the right one for manual brakes and now the pedal is spongy. It stops better but just spongy. No where near where it supposed to be. Do you have to swap the lines around on the master? I have disc front and drum rear.

You likely have air trapped somewhere. Find a connection in the lines at the high point in the system and bleed there.

[IAMN21]

I had the same problem once and struggled to find an answer I used residual pressure valves 1 for front 1 for rear solved the problem and had great brakes