Without starting the engine, push the brake pedal several times. Check if your foot needs the same space each time. Running the engine and pushing the pedal should move it just a little. That means everything is working properly. Begin with the engine off, wait one or two minutes, and then slowly press the brake pedal a few times. If the pedal traveled down far the first sequence but came back up over the following presses, that confirms a fully sealed booster. To check if the booster is airtight while driving, step on the brake pedal until you run out of reserve, then let go of the engine. If the brake pedal still takes up the same amount of distance after keeping pressure on it for 30 seconds, the booster stays sealed. We can't take a power brake booster apart because it's too complicated and too important to how brakes work; the right thing to do is get a brand new or worked-on replacement for the faulty unit. Take off the
Brake Master Cylinder, cut the hose that runs from the engine to the booster, be sure to handle it well so you don't damage it, and pull out the
Brake Lines from the clamp on the car's front end. Remove the clevis pin's clip and pin from where it connects the brake booster to the pedal. Then remove the pushrod clevis from the pedal itself. Slide the booster straight out from the firewall by unbolt the four nuts holding it there, then gently pull the booster, brackets, and gaskets from the engine bay. To install the booster, just do the opposite of taking it out first - tighten all mounting nuts and replace the clevis pin with a fresh cotter pin. Connect and bugcheck the master cylinder first, then finish checking and feeding pressure into the entire brake system. Regulate the brake pedal height and freeplay and make corrections when needed.