If u take off the in line an squirter something like wd40 in it just 3 or 3 quick squirts and put line back on an air it up,do both valves at same time,oring inside is dry,
If drain air pressure off an take the in line off an put a couple of squirts of something like wd40 in it an replace air line,do both valves at same time,an then build up air ,there's an oring inside valve, if truck sit a long time they get dry an want fully seal,,I have also taken the out side air hose off the air compressor an put a whole bottle of rubbing alcohol in the line an reconnected it an built up air pressure to push it though complete brake systems to help clean an dry out any moisture in lines,tanks,brake chambers,etc,
