brake pedal travel

[Gorilla187]

Hey guys i have a '72 F100 that i just converted the from manual drums to power disc brakes..I get decent braking but i have to push the pedal all the almost all the way down but it only comes back halfway i have to pull it back with my foot. ive bled the brakes like 3 times, put new wheel cylinders and brake shoes on the back and manually adjusted them.
what could be the cause of this?? im tryin to get an opinion before i go buy a new master cylinder and booster

[ScreaminZ]

Here's what I would do if I was working on it:

Unbolt the master cylinder from the booster and make sure the piston in there is coming all the way back to the snap-ring that's there to stop it. If that's not coming back all the way then you'll need a new master cylinder.

Check to make sure that the rod coming out of the booster is just hitting the piston in the master when you mount it up so that there's no slop at all.

Unhook your pedal from the booster and make sure the pedal moves easily through the full range and that it's not hanging anywhere. If that's all good, then it's definitely your booster that needs to be replaced.

[Gorilla187]

thanks for the quick reply im goin to check that out right now

[fordman]

when putting discs in you also have to change the master and porportioning valve to a disc master and valve. that may be the problem. as discs require a different master and valve.

[ScreaminZ]

Using the drum distribution block with disk brakes won't prevent the pedal from returning properly. The brakes are just a little unbalanced. My '68 is still running the old dist. block with the '73 disk brakes and works just fine. I've got a proportioning valve ready to go on, just need to get a break from other repairs to get to that.

[fordman]

no it won't keep thepedal from returning. but making sure that all the components are correct would be one thing i would do while i was havign problems. i myself am leaning towards the master not being right. and creating this problem.

[Gorilla187]

The master cylinder is from a disc brake setup I took it off a '77 f150 as for the valve I'm not sure so it must still be the one from the drums.

[fordman]

check out the master if it doesnt return fully or returns real slow replace it. edit dont forget to get the porportining valve or you may have more problems later with unequal brake pressure to the brakes.

[Gorilla187]

so it looks like the piston does come back all the way. so i started adjusting the rod and the pedal is coming out more and more and im noticing that i have really good brakes now! haha i was doing it little by little didnt want to over do it but my niece got sick so i had to stop working on it and leave....
im going to keep goin at it tomorrow but it looks like thats fixing it. you guys have any other ideas?

[ForingaMex]

This is what I was told and it's worked good for me. The proper booster to MC rod adjustment is to have the rod so long that if you push the master cylinder against the booster by hand you have about a 1/16" gap between the MC and booster. Than tighten it down with the nuts. Don't leave to much of a gap or the brakes will lock up by themselves when you're driving somewhere. Don't ask how I know.

[Gorilla187]

so i kept adjusting it and the brakes worked real good and the pedal does come back now but it doesnt come back all the way to turn off the brake lights. what do you guys think? was i supposed to maybe change something else??
i just bought a new MC and booster see if that fixes it.

[fordman]

some boosters also have adjustable rod on the inside where it hooks to the pedal. that can also be adjusted.

[ForingaMex]

so i kept adjusting it and the brakes worked real good and the pedal does come back now but it doesnt come back all the way to turn off the brake lights. what do you guys think? was i supposed to maybe change something else??
i just bought a new MC and booster see if that fixes it.

You can adjust the brake light switch so the lights come on and go out properly.

[fordman]

too.