The brake hydraulic lines may still have to be bled or you may have gotten grease on the rotor.
Bleed the master cylinder.& then rebleed the system.
How to fix brake will not bleed out
Check for leaks under vehicle. You may have blown a hole through a rusty brake line.
you either need a new brake master cylinder or your brakes need to be bled
There is still no fluid pressure. Make sure that the master cylinder was bled as well as the wheel cylinders. New master cylinders can be tough to bleed all of the air out. The new master could be defective.
If you didn't bench bleed the master you need to do that before you install the master.
The ECU for the ABS brakes is attached to the Master cylinder for the brakes.
Make sure the new master matches the old one. Match the depth where the pin goes into the master. The masters are the same.
if back brakes are drum i would think they are worn out not allowing pistons in wheel cylanders to return. also could be valve in master cylander.altho that would cause all brakes to lock up. if disk brakes your calipers need overhauling or replacing
The ECU for the ABS brakes is attached to the Master cylinder for the brakes.
Check to see if you have knocked the brake light switch off of its mount. It is located above the brake pedal.
You did something wrong. -Go back over all steps carefully (preferably with manual) and see where you went wrong.