Brake Problems

[71Prerun]

I have a 1971 F100 with the stock brake setup, manual 4 wheel drums. I put new brakes all around: wheel cylinders, springs, shoes, front brake lines, and a master cylinder. I bled the system after the new brakes and had a soft pedal with lots of travel. I put the new master cylinder on(bench bled first) and bled the system again, the brakes worked ok but started pulling to the left and losing pedal. So I put new front brake lines on it and discovered the right front wheel cylinder was leaking. I replaced that wheel cylinder and bled the front brakes again. Now I have a soft brake pedal with a lot of travel(almost to the floor before any braking) and hardly any braking at all. When I really push down hard on the pedal it pulls to the left. Im gonna tried bleeding the system again, but unsure if that will work. I did not replace or turn the drums, maby thats part of problem. Any suggestions would be appreciated. Also the emergency brake light stays on all of the time.?

[Wes]

1st of all to FORDification, I'm going to say you have a leak,or lots of air, causing your low petal. If after bleeding all the air out your brake pedal still sinks slowly, the master cylinder is by-passing. Is the master new or rebuilt ? As for the pulling to the left, even brake adjustment is critical. Drum surface condition can effect brake pedal effort, and efficiency. Make sure the shoes are clean and dry, that the drums are dry and smooth, and not hardened. Don't forget the rear, can cause a drift pull as well. Your on the right track.

[71Prerun]

The master cylinder is a parts store reman piece. Dont doubt that is causing me lots of problems. Its actually pulling to the right, coincidientally that was the new wheel cylinder I had to replace again, and that side evidently worked its way out?(If possible) giving me a pull to the right. Originally it braked straight, then eventually started pulling to the right. This last time I readjusted it and the thing that holds the adjuster locked into place from unadjusting would no hold on the star nut. Maybe the star nut is worn causing that side to unadjust and causing the pull. I think Im gonna replace the adjusting assembly on that wheel, readjust every brake and bleed the system. Hopefully that will help. As for the master cylinder, who knows if it is the right bore size or if it is working properly, being that its a rebuild from advance auto parts. The first one I picked up two different size wells for the brake fluid, but when I got it home I realized the pushrod was bent. They ordered another one and it had two wells of the same size, so I went to another location and they had two more with the same size wells. Go figure. Thanks for the help.

[fordman]

usually manual brakes have the two different sized resivors. (sp) some other things that can cuase brakes to pull are brake fluid on the pads and drum. if the shoes got any on them they need to be clean. probably replaced. the second thing is the wrong adjustment to tight or too loose and it will pull that way. the shoes should barely rub the drum while you spin it. is your brake light below the ignition switch working when you turn the key on? if not fix that. with a new bulb or whatever it needs. then after you start it make sure the bulb is off while its running. maybe there is a brake imbalance and the adjustment is loose on one side and tight on the other.

[QC]

Are you sure you have the adjusters on the correct side? There is a right and left and if you get them on the wrong side they will screw in instead of out when they self-adjust.

[71Prerun]

Thanks for the replies. The brake light below the ignition switch stays on all the time now, after reading some other posts I think its probably an imbalance too. Thats a good point about the adjusters, Im 99% sure their on the right side because I did one at a time, but couldn't hurt to check. Thanks for the suggestion. The drums are clean and the shoes looked clean, but they could have some brake fluid on them, so I will attempt to clean them, maybe end up replacing them. Thanks again

[fordman]

i was thinking about the adjusters being on the wrong side last night. if i remember right they can go on either way but they can only be accessed if they were put on the right way. i could be wrong . but i think that i am right about that though.

[71Prerun]

Ok. I pulled the wheels off and on the driver side the metal braket that holds the brake adjusted wasn't in the slot. It was suspended by the cable and spring. Guess I didn't have it in the hole all the way. The passenger did have some brake fluid on it from when the wheel cylinder failed, so I cleaned it up. Also the bracket that holds the cable in place was not in the hole, somehow what holds it in the hole sheared off the back, go figure. So I put the an adjuster kit on both sides, adjusted the front brakes, bled the brakes yet again, and... While I was bleeding the brakes the pedal got increasingly better, firmer w/ less travel, then it went away(resevoir was full) the pedal went almost to the floor w/ everything closed up.? So I just continued to bleed the brakes and eventually the pedal got a little better. I readjusted the front tighter and got even more pedal, less travel. So I took it for a drive and the brakes will stop the truck, but I have to push the pedal about 3/4 of the way down until it begins breaking. The pedal seems pretty firm but with entirely too much travel. Could there be a leak in the master cylinder causing the pedal to build up and work good until one point where it goes away? Unsure of how to get less pedal travel and better braking, seems how almost everything is new in the brake system.

[fordman]

the master cylinders do have a bypass valve i think . or maybe thats just in the disc brake masters. if you were loosing fluid out the back of the master you would see it in the cab up where it comes through the firewall. i cant think right now.

[Wes]

IT does sound as if the master is by passing (pressure from the front piston slipping past to the rear piston). Before you replace the master, try adjusting the rear brakes this should get you more pedal. What happens if pump the pedal does it get firmer and higher ? If in fact you do need to replace the master, get a new one, not that much more $$$ and much safer. Good luck

[two-bit]

I had some of the same issues with my '72 when i rebuilt the brake system front to back.
A couple of things i found:
1) i did not have my front drums adj. correctly. I eventually adj. them so tight that the wheel (with tire on it) would rotate only about 1/2 to 3/4 of a turn when spinning by hand.
Because i had them adj. to far in. The first time i stepped on the pedal the wheel cylinders would push out, but not far enough to create heavy friction on the front shoes. The second or third i pumped the pedal it would get ROCK hard and the front brakes worked great. Because i had built up enough pressure to push out the wheel cylinders far enough to create the Heavy friction it needed.
2) You master cylinder should have equal size res. The odd size res. is only for disc/drum brakes. As far as i know. I could be wrong, but thats what i have always seen.
3) you will want to adj. your rear brakes not as tight as your front. Our trucks are a little light in the rear and super tight rear drums can cause rear lock-up.
4) Did your master come with two different rods to fit into the cylinder bore?
If so, make sure you have the right one, otherwise you will be overextending the pedal travel and the rod will not be pushing the cylinder far enough into the master to make the correct pressure.

I'm not sure if i have helped at all. Good luck with your endeavor.

Two-bit

[1971ford]

71 prerun? as in prerunner?

[71Prerun]

Appreciate all the replies. Thats what I figured about the master cylinder. This last time I did adjust the brakes in like your talking about. Their pretty darn tight, which gave me more pedal but not enough. I think I will just buy a new master cylinder, tired of reman parts. And yes I bought the truck with the idea of making it a prerunner, have not got started on the suspension yet, but can't wait. I love classic desert trucks, especially this model Ford. My grandfather had one.

[1971ford]

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