no brakes still

[Dogman1966]

90 Daytona, Has no brakes at all everthing has been replaced from the master, booster, both calapers, both wheel cyl., all brake hoses, new portioning valve. The petal is hard with the motor off, you start it up and the petal falls to the floor and the brake light comes on. I have grav. bleed the brakes and done the pumping bit to same out come. Hard petal motor off, motor on petal to the floor light on. I'm stumped .

[manlystanley]

Originally Posted by Dogman1966

90 Daytona, Has no brakes at all everthing has been replaced from the master, booster, both calapers, both wheel cyl., all brake hoses, new portioning valve. The petal is hard with the motor off, you start it up and the petal falls to the floor and the brake light comes on. I have grav. bleed the brakes and done the pumping bit to same out come. Hard petal motor off, motor on petal to the floor light on. I'm stumped .

Have you gone beneath the truck to see if any fluid is dripping? It seems that when the vacuum boost kicks in something is leaking? On of my cars I replaced the Master, and both rear wheal cylinders--only to then find out that the ABS modulator had started to leak as well.

If there is no leaking fluid, then I guess that you've got air in the system someplace. As a dumb question, you bleed all four wheels?

Good luck,
Stan

[rhandwor]

Look at the front calipers if you install them on the wrong wheels the bleed screw is on the bottom and you can't get out the air. When you install a vacuum booster some of them have a different length on the booster. They are adjustable. lay a ruler flat to cover the hole and measure to the end of the rod. They should both be the same length. Adjust the rear brakes if they are out of adjustment it will cause a very low pedal. A bad hose can balloon and cause problems. Use a flashlight and follow the lines all the way looking for leaks and bad hoses. I think the parts store put the calipers in the wrong box by mistake.
If you installed the wrong bearing by mistake the rotor will move in different places.

[mustangmike351c]

did you bleed the master cylinder?

[KimMG]

New parts aren't always good parts.
Are you losing fluid?

[KManiac]

Your problem is the "Power Brake Booster". That big vacuum can that your master cylinder bolts to. There is a malfunctioning valve inside which is causing the vacuum assist to energize and apply the brakes without the aid of your foot on the pedal. I suggest getting a rebuilt exchange or having yours rebuilt if none available.

Let us know what you do and what you find.

[KManiac]

...ooops! After rereading your post I noticed that you replaced the booster. I alter my original response as follows:

Your replacement booster is defective. Take it back and exchange it for another one. I encounted the same situation once when I replaced the booster in one of my old Chryslers.

Good luck!