Major issues with brakes ?????

[custom cabby]

Here we go...

What I have:
'59 F100, rear drum/front power disc conversion from '71 Lincoln including booster and master cylinder and block, late '70's Ford rotors & new mid '80's Chevy calipers. Newer brake lines.

Problem I have:
When truck is not running, pedal is somewhat stiff but doesn't build up pressure with more pumps. When running, the pedal goes all the way down and finally stiffens when about .5" away from floor, at the same time you hear a lot of air in the pedal movement. When truck is in gear, it barely stops from a roll.

What I have done:
Bled the brakes from pass. rear wheel, to rear driver, to front pass., to front driver. All flowing good and without air. No visible leaks anywhere.

What I'm thinking:
If the master cylinder was bad and leaking around the seal, I would notice fluid loss either in the cab or the outside firewall and there is none. On the other hand I'm not sure what I would encounter if the booster was bad.

Opinions welcome.

 

[BloodSweat&Whiskey]

I have only had one fail and that was over 8 years ago but what you describe is exactly what happened to me. Depending on how bad of a leak you may also notice a difference in how the engine runs. When I removed my booster the rubber diaphram was dry rotted. Basically made a huge vacume leak that if you kept on pumping the breaks you could hear the change at idle in RPMs.

Nothing else that I can think of would cause what you described. At least the booster is normally something easy to replace depending on the car.

BSW

 

[CR55]

Is this a new set up for your truck or something that you've been running without any problems?...CR

 

[custom cabby]

Is this a new set up for your truck or something that you've been running without any problems?...CR

Set up has been on there for a while. The PO did the work and it sat for quite a while before he decided to get rid of it. Thats when I thought it was the calipers and replaced those. I drove it for a day after I got it and then the front tires started to lock up and thats when I parked it and started to work on it.

 

[CR55]

That's a tough one. I would be leaning towards the booster going bad also. Check to see what condition the front brake hoses are in first. Have someone pump the brakes with the motor running and see if they might be swelling. You can also listen for vacuum leaks around the booster and the line running to it. Good luck, I hope you get it figured out!..CR

 

[LOWANDRATY]

Brake problems

If you can hear air when you push the pedal down the booster has a hole in it, unbolt the master from the booster and see if the master is wet on the back side, they will leak fluid into the booster, not into the floorboard.

 

[doggone]

It's the booster, I have had them to do the samething the pedal is hard and goes to the floor when it's running