So I replaced both the booster and master cylinder, and yes bench bled it, replaced both front calipers+pads "SAS"......And still nothing! I have searched for leaks such as a pinched brake line or something but have no idea anymore? Bled and Bled and Bled the system and there is no air in the lines. The pedal is not firm but if I push it to the floor the truck will stop kinda so they are working barely!! I just cant get it to become firm. This is a 93' 3.4 swapped SAS truck and I have the booster line hooked up to the correct port with a one way check valve. Tried taking off all the lines and blowing them out with compressed air, and also inspected for leaking wheel seals..... I have no clue what to go after next. This is the only thing preventing me from driving this rig. Any suggestions???....... before I let the dealer's service center have a stab at it? I'm completely stumped!!

 

Sound stupid but I've seen it happen.. Make sure the calipers are on the correct side. I've seen it happen where the calipers get switched and the system can't bleed itself.

 

yeah I here ya, they are on the correct side

 

Rear brakes properly adjusted??

 

I've had a bad master cylinder before. from advance or autozone. Sounds similar. Do you have rubber brake lines? old ones can budge under pressure.

 

It is a shame posts all over the internet.

All pretty much tell them the same thing.

Then they refuse to accept that some thing is not bled correct or air is entering the system.

Rear drums so worn or rear brakes not adjusted correct.

I have had bleeder valves draw air but not leak fluid.

then it could be anyone of the connections .A little piece of dirt or a nick on threads some place or on a flare.

It is a wonder more of us don`t have problems with dirt on brake connections

Rubber hoses expanding under pressure New China made hoses doing the same

I know I had problems like this over the years working on rusty dirty trucks.

Good luck

 

For what its worth, I had a 71 corvette and after bleeding and changing the master and new calipers, yada yada, I could not get the brakes to firm up. Found out from a vette specialist that the rear wheel bearings were worn(indep rear suspension). The pulsing caliper would pump air into the lines or something like that. Once they replaced the bearing, it was great. Check your front bearings for play.

 

do you have an lspv?

 

Have you figured it out Yet??

 

Yes. I made the dumb mistake of putting the calipers on the wrong side. Remember guys. Bleeders go up! Thanks for the help

 

So, did switching calipers with bleeders up burst your bubble? Funny how that trapped air makes things spongy.
Glad you got it.