New Master and Booster

[one3n3my]

I installed a new Master Cylinder and Vacuum Brake Booster today. I bench bleed the master, reinstalled the brake push rod to the brake pedal, and bleed the brakes.

Now the brake pedal will go to the floor and not return to the original position and still not having any brake pressure to the rear wheels.

I procceded to take the rear tires off to check the wheel cylinders and they are not even actuating for the brakes to work. So here is my question: Why is the brake pedal going to the floor and not returning and what could be causing the wheel cylinders to not actuate the rear brakes.

Appreciate the help.

[MrMeseeks]

any pressure getting to the front brakes? could be a clog in the rear line? Does the rod exiting the booster match up with the back of the master cylinder? I know the sizes can very.
Just things that I would check

[geezer#99]

You need to push in and hold in the reset button on the front of the proportion valve.
Did you have a booster originally?
A booster needs a different pedal ratio. Normally a hole drilled in the brake pedal about 1 inch lower will give you the needed 4.5 to 1 ratio.

[davepl]

Is it possible your pushrod is too long so that it's actuating the vacuum assist, pulling the pedal down, and not letting it go? I've never had that happen, just a wild guess if the pushrod is too long.

[one3n3my]

Yes the truck did have a brake booster originally.

I took everything back out and restarted the install of the new master and vacuum booster. I started the install by taking the push rod and installing that to the pivot and attatached that to the new vacuum booster. Then I continued by adding the bracket to the booster then attached it to the firewall.

I then proceeded to ensure the master was bench bleed for the second time then attached it to the brake booster.

I continued by attaching the push rod to the brake pedal and attaching the brake lines back to the master cylinder.

I connected the vacuum pressure hose to the booster and proceeded to attempt to bleed the brakes.

The brake did not return once again and I have went and lengthen and shortened the push rod to the brake.

I feel like i am missing a step somewhere to why the brake will not return to its original position.

[A1971Blazer]

when you bench bled the MS did the piston move in and out freely?

[one3n3my]

Originally Posted by A1971Blazer

when you bench bled the MS did the piston move in and out freely?

Yes the piston did moved in and out freely. The pushrod had come out of the vacuum booster though when I had picked it up from O'Reilly's.

[Orange Crate]

Did you bench bleed the master cyl. using the plastic adapters and small hoses like this:

[RichardJ]

It is possible you have the wrong master or you have failed to check the pin for proper adjustment.

The Master cylinder on the left is for manual brakes. The brake rod floats in the piston hole.
The MC on the right is for a Power booster.

The pin length on the booster must be checked and adjusted if necessary.

There are tools made for checking, but measurements can be made to check, if you give it some thought