Done SAS to my Ranger....Brake pedal goes all the way to the floor

[driveoverit]

OK I've bled the brakes...put new master cylinder in. Pedal goes hard when engine not running....but when engine is running pedal goes all the way to the floor...Oh yeah 9 inch rear end...so rear abs disconnected...new brakes lines pretty much everywhere
Its a 93 Ranger


I'm stumped

[AKBroncoII]

air in the line. You aren't bleeding properly.

[brendank]

Did you follow the procedure to bleed the master cylinder before you installed it?

[driveoverit]

yes i bled the master cylinder in the vice...I'm going to try to bleed the brakes again today and see what happens

[driveoverit]

ok i bled the brakes again and still it goes to the floor when its running(goes hard when its off)....could it be something to do with the Rabs module??? How about bypassing it??? Does it contain a residual check valve?

[94STXRanger]

Is the vacuum booster working properly?

[driveoverit]

i think you might be on the right track with the booster....when the truck is running and you press your foot to the floor the truck almost stalls out

[94STXRanger]

I would thoroughly inspect the booster. Leaks, hoses, check valves. I wonder if you could have got moister in there or something, or if that would even matter. WIth the truck off press the brakes and then hold them as you turn it on. It sould make the pedal eaisier to press. Thats an easy way to make sure its working. I guess its sinking to thefloor though so it must be.

[driveoverit]

i figured it out...it was the calipers hanging up on the steering knuckles....i have the chevy disc brake swap...there is a clearance issue between the two...i have since ground down the knuckle and a little bit off the caliper....

i think it was the backing plate flexing from being hung up on the knuckle therefore making the brake pedal go all the way to the floor

thanks for the suggestions

[Jspafford]

Thats the same thing that happened to me. I had accidently put in a pad wrong and it was compressing or something and causing the caliper to compress sideways.

[AKBroncoII]

Make sure that it's not a clearance issue with the rotor itself. Not all chevy 44 backing plates are the same. Different years had different hat sizes for the rotors. Not all will work for the swap if you kept the 5x5.5" pattern.