Topic: Brakes quit working...

[Panama85]

I just rebuilt my 85 Toyota front axle and last night I bled my brakes and it was all good. I started up the truck and the brake pressure disappeared (goes straight to the floor without any hesitation) 
Turn the engine back off and after two or three pumps the pedal goes back to normal. What could be causing this? I bled all the breaks and followed the brake lines to make sure everything was connected. Any help is much appreciated. Thank you

[79coyotefrg]

sounds like a bad booster

[Panama85 [OP]]

Is there a way to test the booster or should I just go ahead and replace it? Thanks for the quick reply!

[MiniSimp]

How many times did you bleed the system?
What order did you bleed it in?

I usually have to bleed mine about 3 or 4 times before I'm satisfied with the pressure.

[79coyotefrg]

do  you hear a hissing sound when you mash the brake pedal if so the diaphram, in the booster is bad

[kneedownnate]

How many times did you bleed the system?
What order did you bleed it in?

I usually have to bleed mine about 3 or 4 times before I'm satisfied with the pressure.

X2.  I've heard others say they do it differently, but I always start at the furthest bleeder from the mc and work back from there.  Pass rear, driver rear, pass front then driver front.  You can solo bleed but it'll go much better if you have somebody help, less fluid loss too.

[89toy]

I had the same problem on my 79...no matter how many times I bled the brakes the pedal would always go to the floor.  Made the mistake of killing the motor on a steep ascent (carb pooped out) and I couldn't get it started again so I kept rolling backwards real slowly (never doing that again!).  It turned out to be a bad booster.  Same thing as yours too...If I kept pumping the brakes all was good, but if I held them they would slowly go to the floor.

[Tallchevy]

Check your wheel bearings since this is something you just had apart. I had a truck with 40's & 1 wheel bearing was loose.(I bought it like that) I would bleed the brakes but when it sat for a while or I drove it, the pedal would goto the floor & I would have to pump it to get the pedal back. The rotor was pushing the caliper pistons away from the rotor causing a low or no pedal. It's worth a try.

[Panama85 [OP]]

I'll have to check for the hissing noise when I get home from work. From what everyone's saying, it sounds like that is the problem. I think I will check the wheel bearings before I by a new booster just to make sure its not a quick fix. Can anyone recommend a good place to by a booster online or is this something you would rather get from the dealer?