I am building a 78 F250 4x4 with a rebuilt 400M, four speed transmission and Dana 60 front and rear running gear. I have replaced the master cylinder, booster, front calipers ,rear drums and wheel cylinders. I have tried the search function, but I am not really finding the answer.
I have replaced the booster again and it has not fixed the problem. My parts guy is very familiar with this model truck, so I don't think it is the wrong booster. If you pull the vaccum line off the booster, the pedal will come up. Can you have too much vaccum? I even tried crimping the line, but didn't help. Thanks

 

Bad or missing check valve?

 

Sounds like the push rod is not adjusted correct. You need to have some preload on it at all times between .009-.016 is what it should be.

 

Both boosters came with new check valves.

I don't think there is any adjusment on the push rod on this setup. The booster rod pins on the firewall bracket.

Thanks

 

Yes the push rod is adjustable and is a step in the repair procedure. it is the rod between the boost and the master cylinder. Either sounds like you have the wrong rod in there or its not adjusted. NumberDummy will chime in but there is over 20 combinations of master cylinders and boosters for these trucks and not all of them work.

 

Yes, there is some adjustment on the booster rod. Thanks. However adjusting it to the same length as the original one did not help.
Vin#F26SUBC1406
Pedal part# D7TA LA 02/77
MC# Wagner R97936
Booster # Wagner 5473023
Both boosters have a # stamped 10144
Any ideas?
Thanks

 

I have been trying to get the cab ready to paint, but this brake problem was driving me cazy, so I lubed the linkage and decided to loosen the bolt that attaches the pedal linkage to the bracket on the firewall. You will never guess! Yes. it is fixed. Sometimes it's the little things. Now I can get back to what I am really working on.

 

Congrats on the brake fix, I know where your coming from. lol