Bipolar brakes (1 Viewer)

[hammerheadfistpunch]

EDIT: SOLVED! Brake pedal is firm and consistent. New master cylinder (to replace the old new master cylinder) and a cleaned caliper solved the mushy pedal and the sticking brakes (2 issues).

Just had my brake booster replaced and I've noticed something where, when the car is first started, there isnt much resistance in the pedal and it basically goes to the floor. It firms up in a minute but at stops it starts to go flat again and it can be nearly pressed to the floor again. Then tonight it got REAL firm and got really sensitive. When I got home my front right rotor was 450 degrees (350 front left, 115 each rear) and it stank like burning brakes.
I'm taking it back tomorrow but if anyone has any insights it would save me precious diagnosis time.
New oe master, new oe booster, new but rusted (they weren't painted!) Front calipers.
My theory is that the firm and burning is a rusted slide pin and the soft pedal is something else

 

[on3i11s]

Caliper pistons clean or free of gunk? Brakes bled over and over? Brakes hoses look good?

I'm in the same situation as you...brakes are firm and soft at random times. Now have a squeal that I constantly hear while rolling but goes away once I press the brake pedal. I think I need to bleed my brakes some more to stiffen the brake pedal but as for the squeal I'm at a loss for words.

A year ago my brake pistons were so clogged/dirty that they were seizing up on my rotors and literally slowed the truck down and even caused smoking. Since then I've done a full brake overhaul on my truck. Good luck!

 

[Maleficio]

Look at the last thing you changed before things went South. This would be your brake booster, right? Defective. No?

 

[hammerheadfistpunch]

Look at the last thing you changed before things went South. This would be your brake booster, right? Defective. No?

It was kind of funny like this before the booster, i had extended front brake lines made up and it was like this

 

[Maleficio]

Do you still have your old booster? Maybe reinstall it and see what happens.

 

[hammerheadfistpunch]

The old booster failed mechanically, i cant reuse it

Do you still have your old booster? Maybe reinstall it and see what happens.

 

[Maleficio]

Sucks. Your symptoms are all over the place. But did they not mostly all surface after the booster change?

 

[Tools R Us]

Sounds like the booster push rod wasn't adjusted correctly. There should be slight clearance between it and the master piston, if not can prevent it from fully returning, makes the master build pressure, not return all of the fluid to the reservoir.

 

[hammerheadfistpunch]

UPDATE: they pulled air from the LSPV and it seems to be working a lot better. There is still some soft pedal it idle so I will be keeping an eye on it.

 

[hammerheadfistpunch]

UPDATE AGAIN: the bleed didn't take, the calipers were sticking (rusty slide pins) and the master cylinder was not happy for whatever reason. New [new] master cylinder and cleaned up calipers and it feels amazing. Firm, consistent, balanced...excellent.