Replaced caliper, bled brakes and still no pedal pressure

[Mossyoakglock]

So I replaced my front left caliper today and bled the brakes twice.
There were no air bubbles what so ever so I'm sure that I got all the
air out of the system. I used a pressure bleeder.

I went to test drive it and still have no pedal pressure. With the truck
off I could pump the brakes 3 or 4 times and they would be solid as a
rock and hold. When I would drive I could pump the brakes and about the
3rd pump it would return to normal pedal pressure and hold until I
stopped. Once I let off the brakes to accelerate and brake again, there
would be no pressure.

I checked all lines and the master cylinder and there are no leaks
anywhere. When I pressure bled, I used 10 psi and it held there all day
long.

What else could be the problem?

I'm taking it Monday to the dealer so they can bleed the ABS system and
fully flush the lines. When I changed my brakes two weeks ago and had to compress the calipers back in, could I have introduced air into the ABS system?

[Carder09]

Did you bleed all the brakes in the correct order?

[Mossyoakglock]

I did the following tests to make sure I was getting a vacuum.

 

Test for a system vacuum leak as described below:

• Operate the engine at idle without touching the brake
  pedal for at least one minute.

• Turn off the engine, and wait one minute.

• Test for the presence of assist vacuum by depressing the
  brake pedal and releasing it several times. Light application will produce less and
  less pedal travel, if vacuum is present. If there is no vacuum, air is leaking into
  the system somewhere.

Test for system operation as follows:

• Pump the brake pedal (with engine off) until the supply
  vacuum is entirely gone.

• Put a light, steady pressure on the pedal.

• Start the engine, and operate it at idle. If the
  system is operating, the brake pedal should fall toward the floor if constant pressure is
  maintained on the pedal.

As I also said, when I was using the pressure bleeder, it would hold the 10 psi the whole time and wouldn't drop. There was a slight leak at the cap since it wouldn't seal properly but that was it.

[Mossyoakglock]

I did. Right Rear > Left Rear > Right Front > Left Front (the one I replaced).

 

I bleed them twice. Once by myself and the second time I had the wife watch and make sure nothing went dry and the pressure never dropped.

[Mossyoakglock]

Well went out to the truck this morning and there is a very small leak where the master cylinder bolts to the vacuum booster. I'm guessing the master cylinder is bad? Do I need to replace the whole thing or can I just replace the seal?

[Mossyoakglock]

It was a simple bleeding process which was easy and worked fine. It's the master cylinder that is bad which was either bad before or I cause it to go back because the pedal would go to the floor.

 

I'm was looking to see if anybody else agreed that the master cylinder is bad. It's probably leaking just enough to where I don't have break pressure when using the pedal but enough of a seal that it did not affect the bleeding process.

[Carder09]

Mechanic time. Brakes are a life and death kind of thing.....

[gmtech4]

always do brakes in pairs ,,,,,,,do 1 side ,,,do the other

[jdnoble18]

You bled in the reverse order, but I dont think that would cause what you are experiencing. You are supposed to bleed closest to the master cylinder first so, LF, RF, LR, RR.