1992 fruehauf fuel tanker air leak.

Hello everybody I have a fuel tanker that leaks down air when I'm at the loading terminal mainly will leak when it's below freezing but will still leak in summer temps sometimes. I can load about 3000 gallons before it drops to low and I have to build my air or get red lighted. Problem is I can't get it to leak unless I'm loading or unloading and it won't leak all the time. Have looked all over for an air leak as well as added anti freeze to the air lines. Any tips or suggestions would be greatly appreciated thanks, joe

 

Thanks for the reply. I will check that tomorrow morning and see what I can find. Thanks for the information