Why do i have loss of brake pressure

If you break fluid level is correct and your break pedal goes down to the floor means that your master cylinder is going bad and you might loose your breaks completely if not checked or replaced. Your breaking system is down to the last O ring inside the master cylinder, once that rubber O rings goes you will not have any breaks at all. Master cylinders have a number of rubber O rings that work like a plunger or piston that produce pressure within the breaking system. When the first one wears down due to age, your pedal begins to loose break pressure and you have to pump your breaks several times to gain breaking. You are now down to the last rubber O ring and a warning that your master cylinder needs to be checked. You can still use your breaks but only for a few days before the other rubber O ring gives out too. Once both O rings give out you completely loose your breaks.

1-change brake master cylinder it has damage o rings that losses break due to its age

2-also try to check all hoses pipes for break oil leak include under car pipes that connect master cylinder to the rear wheels

3-check pressure pipes that connect master cylinder to cylinder head

regards

Check one of the breeders it may be loose or not put on properly.

air must be entering the system somewhere, check all wheel cylnders for leaks, and check the master cylnder for leaks( some cars's master cylnders leak at the firewall and fluid runs down inside the car under the carpet)

you're on the right track , three things that relate to the brake light, loss of pressure, fluid pressure and parking brake, go to it

Sounds like a brake line is cracked and leaking. Stop driving that car until you fix this. Break fluid leaks can cause sudden loss of hydraulic pressure and a complete break failure.

They should. Can they turn the rotors

Yes you can disable ABS. First, You said you loose brake pressure. Does your brake system have a vacuum booster and a master cylinder or is the master cylinder abs hydraulic assembly all built together?

you still have air in the system,you need to cross bleed the system,RR,LF,LR,RF.if this does not work you might try picking up a hand operated vacum pump to help get all the air out.

you might check your brake fluid. if it looses preasure than regains it after a second it may be low on fluid allowing air to get into the lines. you might need to blled the breaks to get all the air out of the line. if you need instructions on how to do that let me know.