OK so I replaced a front right caliper on my 93 4runner sas 35 12.5s 22re everything went perfect but brakes where very low and almost did not stop me. I and a friend who is a master ase guy with gm bleed the brakes and got a little more pedal after a couple more cracks of the bleeder the pedal was nice and high. I started the truck and the pedal went to the floor no brakes. So we replaced the master cylinder same thing then the it was a new brake booster still the same thing at wits end please help

 

You sure you bled thoroughly and topped off after each parts replacement? No leaks?

 

yep lose all pedal soon as it fires up

 

Your sucking Air someplace .

All it takes is one spec of grit in a flare fitting .

Bleeder not sealing .

Your New Caliper has a problem ??

These can sometimes be a real pain to get all the air out of the LSPV lines when the valve is so rusty trying to remove the bleeder gets real expensive .

 

Just wondering... I think the system could only suck air from the booster vacuum, right? And vacuum leak would cause hard pedal but not cause it to go all the way down to the floor?
If bleeder not sealing, there should be a leak.

 

Let me see if I can get this straight.

Does the pedal feel fine when the truck is off?

Then when you start the truck the pedal goes to the floor?

What brake parts are you using? You probably did some modifications for the SAS, right? What modifications did you do?

 

yes rock hard when off
yes falls to the floor when truck is started
stock disk front drum rear was never an issue before replacing caliper that froze up