I have a 1977 F150 4x4.
My pedal has a lot of travel (about 1.2-2")before the brakes grab.
I have new pads in the front, new shoes in the rear.
my rear cylinder was leaking so I replaced both. I even installed a new T-line to the rear axle at this time as well. I flushed the entire system starting from the wheel furthest away from the master. I bled each wheel till fresh clean fluid ran through. I did notice that the rear brakes never bled with much pressure. The fluid kind of dribbled out while the fronts shot out with lots of pressure. I also replaced the master just because it was old.
I don't think it's the booster because that would usually lead to a hard to press pedal.
I do have old front brake lines that the outside rubber is showing age cracking. yet they do have great pressure. could it be the proportioning valve? Any other ideas?

 

Did you bench bleed the master before install,
And did you adjust the rears until the adjuster could not be turned anymore then back it off???

 

yes I bench bled as well as gravity fed the brake system before bleeding. I have set the rear drums to let the wheel spin about one and a half rotation. I also use the parking brake everyday to ensure that it keeps adjusting the drums.

 

Sorry to revive an old thread but did you ever fix this? I have the exact same problem after replacing the rear wheel cylinders. Only oddity to add is that the pedal firms up when the ebrake is on (seems to me this rules out air in the system). any tips might save me alot of headache.

 

NuMex........sounds to me like you need to adjust the brakes up..........

 

To much travel in the brake pedel could be a few things. In Muladesigns1's case id ask if when he replaced the brake booster did he make sure the shaft on the booster mached the length of the old? You need to unscrew to lengthen (more boost) or screw in to shorten (less boost)

 

got it figured out... I just didnt adjust the rear brakes properly when I redid them. adjusted em up and theyre as solid as a rock... apparently i had the wrong thought that they are "self adjusting" , maybe "self adjusting" after theyre adjusted... preciate the input tho fellers

 

Yep, self-adjust after intitially adjusting them. After backing up (say a driveway, parking lot) and hit the brakes they might ratchet one sprag. So if the brakes are waaaaaay out it would take backing up 50 times to make any effect.

Josh

 

im hitchhiking this thread...

my pedal is also soft and needs pushed down about halfway before the brakes grab (it also normally is sticking up a good leg lift higher than the gas pedal which is very annoying).

the front reservoir of the master cylinder empties itself out after about a week or two of daily driving. a ford mechanic took a brief look at this and also checked the rear brake lines and fluid was making it there when you pump the brakes. The previous owner told me the master cylinder is new within the last few months.

what may be the cause of the master cylinder reservoir continually leaking out and the pedal issues? I would like to pull a trailer but won't do it until my brake system is a little safer. Any advice?

 

Need to carefully check the rear wheel cylinders for leaks. Peel the rubber back and inspect.

 

$830 in parts and labor later, it appears the front reservoir is still emptying out.
The rear brakes are working, after new wheel cylinders, axle seals, hoses and lines, but the master cylinder is still wet on the outside from the fluid. the rear reservoir has stayed completely full for the past two weeks but the front one is already about half empty. What is the next place to look?

 

When you say the front reservoir are you talking about what it controls or its physical position? the forward small reservoir corresponds to the rear brakes and the aft large reservoir corresponds to the front brakes

1. Inspect your lines all the way from the master cylinder to each wheel. there should be NO sign of fluid on them. You may have a hairline crack in one of the lines causing the spongey feel and loss of fluid, which would cause the line to look wet in some place. Also look at your calipers (or front drums) for any signs of fluid, again there should be no sign of fluid. A severely discolored rotor could also be a bad sign that the fluid is leaking from the cylinder onto the rotor.

You should only need to inspect the lines from the reservoir thats losing fluid.

2. Your loss of fluid could also be from a poorly sealing reservoir cap, but this would not explain the spongey feel, only explains the wet looking MC.

3. I guess it could be possible that the MC is cracked. wipe up the MC, then have someone depress the pedal and hold it while you watch for any sign of new fluid.

good luck.

 

Well the spongy feeling is 5x better after I had the rear brakes done, but I'm not sure what it should feel like when all is working right. The brakes are working fine and if I hit them too hard the rear wheels lock up now with no problem at all, but I still need to press the pedal down probably 1/3 of the way before it starts slowing the truck.

 

Converting my rears to disc, with hydroboost and 90's hd master was the best mod I have done to the truck. After years of piddling with the old brakes, I did away with all the problems and it stops on a dime.

No matter what I did with the old system, it just never made me feel safe. Now I do.

 

update: the brake shop said the master cylinder must be faulty so they are replacing it. So all in all I will be about $950 in total for the brakes and hopefully there will be no more leakage - but everything should be running like new! and on top of that I wired in a trailer brake controller so hopefully will be nice and safe.