i have a 78 and the brakes work but i have to press all the way way down, i bled the brakes and i have new drilled and slotted rotors and new pads i think it might be the brake booster. HELP!!!

 

Pressing all the way down is usually air in the brake system. Brake fluid doesn't compress very much and converts force to PSI which the calipers convert PSI to force on the pads /rotors.
Air in the brake lines reduce the amount of PSI that can be achieved . Meaning you need more pedal travel to produce a given PSI in the brake system.

So air can mainly get trapped in 2 locations.

1. master cylinder.
2. caliper piston bores.

Air can also be introduced from a leak. Usually leaks are in the caliper pistons. This is usually seen when you replace the brake pads. Anything wet on or near the caliper pistons ?

Next depending on what calipers / piston design. (lip seal or o-ring) rotors that have a lot of run out will pulse the caliper piston's and push air into the caliper piston area.

The bleeding method you use is depends on why you are bleeding.

Complete open system from a brake line, caliper , flex hose , etc is different than just flushing a closed system.

A closed system that was / is working properly you have more options. Gravity , suction , pedal pressing , pressure

On a open system from a repair usually you need to pressure bleed and also reduce the places where air can get trapped. This is where most people have problems. Search the forum there are many posts with people having problems bleeding after the system has been opened.

It all starts in the Master Cylinder. If this has air your brakes will never work properly. You get air in the MC usually because of the leak at a caliper which empties the MC bowl. Or during a bleed process and again you empty the bowl.

Read my post # 11 (link below) on how I bleed my brakes. I use my car for track days , so brakes are #1 on the list of maintenance things to check before and after each event.

https://www.corvetteforum.com/forums...-a-sudden.html

 

Keep in mind the booster is strictly an assist. The booster allows you to "lock-up-all-four" with your big toe, barefoot. It has little to do with a pedal to the floor issue.

With the engine off, no booster involved, does the pedal still go to the floor? I bet it does. Like cagotzmann said: leaks or air or both.

 

i replaced the booster because im replacing most of the parts and its tighted up a little, the pedal doesntgo all the way to the floor but i can sit there and and pump and pump (not all the way down) but the pedal dosnt go stiff

 

I had to buy a brake bleeder from Motive

for 67 dollars you get the pump as well as the adapter to your master cylinder

Pump the unit up to 15 psi

Go to farthest wheel and crack open the bleeder

repeat for the remaining wheels

Only way I was able to get enough air out of my lines

good luck