72 f100 4x4 brakes bleding off ?

[airrikk17]

after i redid my brakes on my 72 f100 ( all drum) when im sitting at a stop light the pedal slowly drops to the floor, and if im there long enough it feels like theres no brakes at all. i thought it jsut needed to be bleed off again and after 3 times of bleeding them off , it still does it. not as bad as the first time though. am i not bleeding them off enough? have i been bleeding them the wrong way ? am i missing a hose for the booster? sny help appreciated .

when i bleed my brakes i start at the right rear , wit hthe truck running , have my buddy pump the brakes then hold , then i open the bleeder , then close and have him pump again, after i dont see any air coming out i , go to the left rear , , then the right front , then the left front . oh and i continually keep checking the fluid level to not let it get low also.

is there a better way to do it ? or is it something more serious?
i did not rebuild the plungers when i redid my brakes , something i think i probably should have done since they were tore all apart anyways. but i also have not seen any fluid leaking so, i dont think they are bleeding off at the plungers.

please help.

airrikk17

[FORDification]

You're bleeding them correctly, except that it really isn't necessary to have the engine running (and actually probably better that it not be running).

Kinda sounds to me like your master cylinder is bad...the plunger seals aren't holding the pressure, allowing fluid to bypass them.

You say you 'redid' the brakes....can you define 'redid'? Just the shoes? Did any of the brake cylinders get opened up?

[airrikk17]

new shoes and new drums for the front , just new shoes for the back.
the lines were discinnected fro mthe front and all new bleeders were installed on all 4 .

i did not remove the rubber on any of the brake clyinders.

bad master clynder , makes since.

is this a rebuildable part ? or all new replacement?

ive rebuilt the master slave clynder on my toyota before .

thanks

airrikk17

[FORDification]

You could probably buy a rebuild kit for yours, but considering a complete remanufactured unit is only about $25, I'd just get a replacement.

However, since you did mention that you had lines disconnected and replaced the bleeders, it's very possible you simply have more air in the system, especially if the brakes were working fine before the brake job. I'd continue bleeding them before replacing the master cylinder. You might try gravity bleeding...just open the bleeder valves and keep the master cylinder full. It'll be a lot less work than continually pumping them up.

[68F250]

Be careful, I think your master cylinder is going out. You got the classic symptoms. Is is wet behind the cup where the pushrod goes into the master? It could surprise you one day with no pedal on the first pump, usually happens when coming up on a red light. Just let up all the way and give it another pump.

Hopefully you'll have it repaired before that happens. For me, I'd go with a new mc. I used to rebuild them myself but nowadays I don't think the savings or hassle are worth it.

[airrikk17]

well that definitly confirms it , ill be replacing the master clyinder. i definitly dont want to run into anyone else , especcially with a full load going to the dump or a load of lumber for my shed.

my truck is at home and im at work , ill definitly check into it whe ni get home , but i think ill be repalcing it anyways jsut to be careful.

thansk again

airrikk17

[airrikk17]

well i tried replacing the master clyinder today. the part i got from napa , was not correct as far as the push rod is concerned , everything else looked correct. so i tried to salvage the old push rod and it sort of works.
now , the problem im getting is a really hard brake pedal and what sounds like a vacuum leak as i press the brake pedal.

i brought the push rod to napa to try and find the correct one , but they didnt have the kit in stock and its special order , 2 weeks out.

what i did find was that i have a brake booster , or at least i beleive thats what it is. large round canister looking thing closely attached to the firewall with one large vacuum line hooked to it and then the master clyinder attaches to it.

can someone help me identify what year this brake booster is from so i can order the correct kit.

as far as i have read the 72 f 100 4x4 's didnt come with a brake booster ( 4 wheel drum brakes ) , this also could be a 71 f 100 , theres so many parts and piecs that arent from the same year truck on this its hard ot get the right parts the first time.

when did the brake boosters become availble on ford 1/2 trucks?

has any one else ran into this problem and found out what year it came from?

the push rod has what looks like about a inch to inch and half round plunger on one end , the end that goes into the booster. from there it looks like theres another push rod in side the booster that goes to the brake pedal and is attached with a round loop hole type rod , that is adjustable. it is currently adjusted all the way in.
the push rod i need is the one from the master clyinder to the booster. right now all i could do was place the rod in side the master cylinder, and it does not attach to anything in there. jsut rests inside.

could the vaccum i here when i push the brake pedal in be a bad booster?
could the hard brake pedal be because i dont have the correct rod and master cylinder combo?
the brakes feel weak even with the hard pedal.

would anyone happen to have a diagrahm of the mater cylinder and brake booster im talking about , possibly with part numbers ?

thanks , sorry ive rambled , but im tryingto get enough info that some one there can help me out.

airrikk17

[fordman]

it sounds like a possible bad booster.

[NM5K]

well i tried replacing the master clyinder today. the part i got from napa , was not correct as far as the push rod is concerned , everything else looked correct.
........................................................

Yea, I think they must do that to everyone.
We've bought new master cyls for both my trucks,
and both were wrong. If you buy a master for a
67-72, I'm pretty sure they are giving you a newer
cyl from a 70's? truck, or whatever. I know for one
thing, they don't fit right. I bought a new one for my
68, and #1 it didn't fit right, and #2, it was bad right
from the start. It would suck in air every time I
tried to bleed it. I finally noticed it by using clear
plastic tube to see the fluid/air flow. Every time
I would pump it to bleed, it would let in a burst of air
to my right front cyl mainly. In perfectly spaced
air/fluid intervals.. I put my old one back on, being
it wasn't actually bad yet. I still need to take that
new one back and get another...haven't had time..
But it's a lifetime warranty, so I've been in no rush.
I don't know why none of these master cyl co's can
give out the correct unit, with the right length rod..
I hear of this all the time.. Silly I think.. Who wants
to lose 2-3 inches of pedal... :/
MK

[airrikk17]

i dont think the master cylinder is the wrong one other then the rod type and length.

did you bench bleed your new master cylinder? the first time i tried mine and didnt bench bleed it , i would get no resistence at all. then i decided to actually read the directions that came with it. so i took it off and bench bled it and then thats where i started getting into problems , major resistence, and the air sucking sound when i depressed the pedal with the vehicle running, im thinking its a bad booster , although before it seemed to work fine , at least no noise before, or it could be because its not the correct push rod and something is not fitting in the booster correctly. im hoping for the later , since ill have ot be replacing it anyways.

airrikk17

[NM5K]

Well, I guess the cyl itself is ok, but it's fer sure
different than what was on it. But if they are
going to use those 70's model cylinders for 67-72
app's, they should at least give the right length
rod. One goofy thing...On the 74, we put a new
one on it about 2 years ago, and the cyl itself
looked about the same as the one on it, :70's style",
but again, the pushrod was the wrong length.. It was
usable, but I had to tape a nickle to the back of
the brake pedal lever so the light switch would
cut off. I hate having to do funky stuff like that...
BTW, yea, bench bled it first, and then slapped it on.
Didn't work, and bled it many more times. It was
fer sure bad.. Sucking in air every push..
I put my old one back on, and was fine right off the
bat. The old one is still on there... If it does go,
I'm going to give serious thought to rebuilding it
vs slapping my new one on. " I can get the bad new
one replaced no problem, but hate the pedal height
with it's present rod. It was really low.. My old one
sits up high about even with the clutch pedal.
MK

[cdeal28078]

ost of the rods that are around 1/4" have an adjustable end on them. It's not alot of adjustment, maybe an inch but it's there. I used this on my 71 to lower my brake peddle closer to the floor so I would'nt have to lift my foot off the floor to hit the brakes, I have an automatic though.
There is an adjustment specification for this in most of the shop manuals. Maybe this is what you need.
As far as a vacuum leak, does your engine start running rough when you hit the brakes? All power brakes will make some noise when you mash them or at least mine does and it stops great.
I am pretty sure that power drum brakes were available on these model trucks.
clint

[NM5K]

I looked for an adjustment on mine, but didn't
see one.. Maybe I just missed it.. But I didn't
notice a part that unscrewed or anything.
Mine are not power. I have considered
adding a booster and making them so, but
haven't got around to it. On my bad booster,
the air seemed to be sucked in through the
back where the rod goes.. If I got under the
dash and pushed it, you could hear a slight
hiss on every push or release. Yep, pretty
sure power brakes were an option. I think
about all you add is the booster, and you are
converted. I think you do have to change to
a P/B master cyl too if I remember right...
I wanna do that some day..
MK

[airrikk17]

well, i fixed my problem , sort of . i removed the booster and am now running with out a booster. everythnig seems ot fit right , brakes work. definitly odd sincei m usedto power brakes. but its getting me by .

thanks for the help.

airrikk17