Pickup brakes

[Slowpoke]

I went to use the '79 Ford PU and the brake pedal went to the floor with no braking. Of course, it had low pedal for some time, so now I was forced to do repairs immediately. So I ordered a rebuilr Wagner master cylinder and followed all instructions for bench bleeding, installing, wheel cylinder bleeding, etc. Guess what.... the pedal still goes to the floor with no brakes. I can pump it up and it will hold about half way, but if I let off pressure for a few seconds, it goes right back to the floor.
I am thinking a defective rebuilt master cylinder. Can it happen?

 

[anonomous]

Can happen. But look at the booster.

 

[the tractor vet]

Myself i would be looking for wet spots under the truck then i would be checking the proportioning valve then we would move on to adjusting the rear brakes . As you have other problems then a master cylinder.

 

[old]

Bad new master cylinder, leak in one of more of the slave cylinders, line with a hole in it.

 

[NEKS]

Back in early 90's was putting a master cylinder from NAPA on a 1964 F600 and went through three of them before finding one that would work.

 

[Hobo,NC]

(quoted from post at 18:32:41 07/11/10) I went to use the '79 Ford PU and the brake pedal went to the floor with no braking. Of course, it had low pedal for some time, so now I was forced to do repairs immediately. So I ordered a rebuilr Wagner master cylinder and followed all instructions for bench bleeding, installing, wheel cylinder bleeding, etc. Guess what.... the pedal still goes to the floor with no brakes. I can pump it up and it will hold about half way, but if I let off pressure for a few seconds, it goes right back to the floor.
I am thinking a defective rebuilt master cylinder. Can it happen?

Plug off line conections at master to confirm its bleed out are good,,, Then I first would pinch off all the rubber lines to confirm the issue is not in a wheel/brakes...

I have had so many problems with Wagner brake parts I refuse to use them,,, Does not mean yer wag master is defective,,, my main supplier switched fro Bendix to wag,,,, they have lost a customer over sorry wag parts,,, I refresh their memory every chance I get

 

[david from mo]

Adust your rear brakes , classic pump up adjustment.

 

[504]

Did you inspect the rest of the system, or are you just throwing parts at it, and then blame the parts that don t fix the parts that were t broken in the first place.

 

[ericlb]

if you can pump up the brakes and they hold, untill you let off the pedal, your rear brakes are out of adjustment thats all it can be, over time those adjustment
wheels get rusted, and brake dusted until the little metal tab that is supposed to move them just cant, then the brakes wear untill you get very little brake action on the rear,and a very low brake pedal the proper fix is to tear it down and clean everything, and replace the shoes if needed, if you do also replace the springs and hardware, if you dont want to do all that at this time, raise the truck off the ground one wheel at a time [ i shouldnt have to mention this but block the front wheels] put the truck in neutural and take a screwdriver and adjust the star wheel until the brake shoes just barely scrape the drum when you turn the rear wheel, then do the same to the other side, see if that gets it right for you

 

[Slowpoke]

I did adjust the rears, although they are pretty much out to max. I wanted to avoid replacing them now, but it looks like I'll have to and see if it solves the problem.

 

[Slowpoke]

No leaks whatever, anywhere.

 

[Slowpoke]

The old booster would not hold a vacuum, so I replaced it along with the master.

 

[Slowpoke]

Yes, of course!

 

[old]

Bad new rebuilt master most likely then. Now days not uncommon to buy bad new parts right off the shelves. Just look at how my water heater problems are this stuff made in China only lasts a few days if your lucky

 

[bc]

I'm 3 days late here but if all else fails check the vacuum hose and system going into the booster. Gotta hold a vacuum.

 

[trucker 40]

If you have to pump them up,and its not leaking anywhere,and your back brakes are adjusted,it sounds like you didnt get the master cylinder bled good,or it was bad out of the box.You have to bleed it good with the hoses that comes with it under fluid all the time.If you are by yourself it might be a little hard to do.Ive done it by myself before and had to rig up something to hold the plastic line in the fluid.If you did that,then its probably just bad.

 

[Slowpoke]

I have made up metal brake lines just for bench bleeding master cylinders. They stay put in the fluid.

 

[Hobo,NC]

(quoted from post at 01:40:04 07/13/10) I have made up metal brake lines just for bench bleeding master cylinders. They stay put in the fluid.

Rubber tubes are metal lines are a joke,,, just block off the ports with your fingers are the rubber plugs are if you are lucky the master came with block off plugs (best thang that rebuildes have came up with for bleeding),,, just keep work'n it till you can not move the piston any.... you can see the air being forced into the reservoir,,, when the air is gone its ready to install,,,, tubes aerate the fluid to much ,,, you will never get all the air out with then unless you are genital with bleeding it...

Next mount the cylinder and leave the lines a tad loose,,, have some one slowly press the brake pedal,,, when the pedal is close to the bottom tighten the lines,,, replete a few times ...

Still laughing at someone think'n you have a hole in yer brake line,,,, if you can build a pedal a hole is not your problem,,, in this case the booster would not be a issue,,, it is on late model chebbys tho... late model chebbys are in a class of their own :twisted:

Have you adjusted the rear brakes till they lock,,, have you tried to clamp off the flex line to each wheel are axle...

 

[36 Coupe]

Replace the worn linings.

 

[36 Coupe]

Replace the worn linings.