I have a 1997 Chevy 1500 Sillverado 2wd with a 305 in it with an automatic transmission. The a/c is blowing warm and it took a charge but when we removed the gauges the refrigerent started to spew from the schrader valve. We tried to free up the valve while contaminating the shop and atmosphere but the valve remained stuck open. Is this valve serviceable or do i have to buy the whole a/c line and block assembly? At least we know where the leak is!