Help with the brakes
Hey guys, i'm relativity new to older cars and cars in general but i have a 1975 GMC suburban that has a problem i cannot quite locate. when the car is off i can pump the breaks and the first couple times it sounds like air is coming out of the break pedal or around it and then it builds up a slight amount of pressure. after i turn the engine over the breaks build no pressure at all and im left with the air sound. when driving i have no break at all when pushing the petal down up until the very last inch or so then it breaks rather slowly. i have yet to bleed the breaks but i havent done any break work on the car so i do not know how air would have gotten into the lines in the first place. Any help is great help, thank you in advance.