ok i change my master brake cylinder because i was told it was going out. i bled my master cylinder and i bled my brakes. when i hit the brake its very light. could i have a leak in one of my brake lines. it feels like a pressure problem but idk

 

Just not bled enough! pump the brakes 20 times then open the valve while the brake pedal is to the floor and pull it back up like ur doing a clutch till you feel good pedal pressure

 

yea yo i did all that. it was good till i started the car.

 

dont you need to do it with the car running because of the brake booster running of a vacuum?

 

thats what i thought but my friend told me it doesnt matter.

 

Assuming you got the bleeding air out of the system ........
You should have bench filled/bled the master before installing it ......

Sometimes you may need to adjust the length of the push rod from the pedal into the vac assist from inside the car, it's got a 12mm nut and the rod is threaded, make sure you don't overdo it, there is a procedure in the manual for getting the right amount of play referenced to the pedal height from the floor.

 

Uh to be honest..i flush out my brakes also a few weeks ago myself...and i had the car on cuz i noticed that when the cars off that the brake pedal has tons of pressure but when i went to turn it on...it was spongy...so i bled them with the car on....make sure u do right rear, left rear..right front then left front...