STRANGE AIR LEAK...NEED HELP

well, this isn't going to make any sense, but here goes. every two weeks or so all the air will leak out of my truck overnight. i wake up in the morning fill it back up to 140 psi, and it won't leak again for another couple weeks. when it is leaking, i check everything except getting behind my gauges but they haven't leaked in almost 3 years so i don't think thats the problem. regardless of that, the only thing i could think of that wouldn't leak constantly was the valves. like maybe they get stuck open a little bit every once in a while. well last night, while the air was leaking out, i put air in all the bags and they stayed the exact same after 2 or 3 hours, but the tank pressure still dropped. i even plugged the dump valves to see if the fill valves were leaking, nothing. i am completely stumped. if its not the valves, there wouldn't be a leak anywhere else that would only do it every once in a while, it would just leak until i fixed it. i plugged the compressor inlets also, so air isn't coming back through them....any ideas

do you have a water trap and is it closed all the way

well if you have check valves on the compressiors like you said to keep air from coming threw the comp. then u might have some trash in the valves such as teflon tape or anything. something happen to me like that on a car at the shop i had to take apart the valves and clean them out as well as the rubber gasket that goes in them. try that if ya have time

we had a truck at the shop do this, tried everything, ended up that a little air was getting past the check valves on the compressors and leaking. new check valves fixed the problem.

ya i forgot to ask if you had viairs cuz we always take those stupis leader hoses with the check valves on them off and just put some other ones on but none of the newer viars we had an problems with

my truck does the same but i know its one of my back fills i washed my truck and i saw little bubbles comin out my valve close to were the solenoid is

thanks for the response. i don't have water traps, i have drain plugs on the bottom of the tanks. i have two viairs, both leader hose check valves went bad. i put smc check valves on the ends of the hoses to fix that. one of the smc check valves will fail occasionally and let air come back through the compressor, but most of the time it works fine (i find that strange too). never the less, i screwed a plug into the air filter inlets of the compressors and the tank still leaked. i also said i filled the bags with air and screwed plugs in the dump valves so no air could come out, and the tank still leaked to 0. so its not the compressors or valves. thats what doesn't make sense...that only leaves the fittings and i dont see how a fitting could leak only once every two weeks.

well if you have firestone bags, i`ve had tons of those leak air out of the bottom bolt hole where people over tighten a bolt that was maybe to long, and i have even had them leak out around the rings....firestone and conitechs

but it is weird i had a blazer that did it and it was my bags but that wouldnt explain why its leakin out of the tank so but its all a trail and error thing

if you have compression fittings, the more pressure you have behing the fitting the less likely it will leak. less pressure on a slightly loose compression will cause air to leak out. if you have copper with ptc fittings, hot and cold will cause the lines to contract and expand at different temperatures obviously. just throwing that in there, idk if you have dot or copper lines with ptc or compression fittings.

Even if you plug the inlet of the viairs air will still leak out of the body of the compressor.

Check the pressure switch ive had a viair pressure switch leak from the terminals before, crazy huh