Intermittent air leak

[Lee Bradley]

My conversion of a Neoplan Cityliner continues; going back together I think.  Decided to check for air leaks while the air system is completely exposed and mostly accessible also time to remove some subsystems; kneeling system gone (along with its wiring) air operated doors gone and replaced a splice, the PO had used to repair one of the main brake lines, with a complete new line from treadle pedal to a relay for the rear brakes. Changed the left to right leveling from the front to the rear and added Pete's leveling system. Chased lines from one end to the other with squirt bottle of soapy water. Tightened, re-sealed, and replaced fitting and hoses. The bus has been on life support for months (plugged into shop air) and the shop compressor comes on less and less frequently.  Hooked up the leveling system and no more leaks the shop compressor is silent.

Aired up the suspension with the leveling system and all is well. I can rise and lower the front and rear and lean the bus from left to right, life is good. There sits the bus in the attitude that I put it in and the pressure gauges are rock solid. Then about a week later I come home and the bus is listing to the right, the right rear suspension air pressure is zero. I go to the leveling control panel and re-inflate that corner and go in the house. 30 minutes later, zero again. Re-inflate and it stays up for 5 or 6 days or an hour. I have the tag axle tires off for access during the conversion so that air bag is not doing any thing so I disconnect it from the system and the air leak is gone ... for five days. System at zero but I have noticed that if I inflate the suspension to 75 psi it will stay up for about a week if I inflate it to 65 psi it is zeroed in 30 minutes to an hour. Tuesday I filled a bucket with soapy water and inflated that air bag to 75 psi and soaked that bag with soapy water...nothing.  I then lowered the pressure to 65 psi and as the bag rolled around the bottom a line of bubbles about 6 inches long appeared where the fabric was flexing.  Small enough leak that the bus compressor would have no trouble keeping up on the road and if I parked in a location where that bag was extended there wouldn't be a leak but if that corner was on high ground that bag would be in a flexed position and would drain the air system probably overnight with the OME leveling valve supplying air to it to keep the bus level. A new air bag is on order.   

[JackConrad]

Lee,
   That is very interesting. I never would have thought to do a check like you did.  Now, if I can just remember that procedure LOL  Jack

[bevans6]

Good for  you!  Leak in an old rolling lobe bag where the lobe was most worn during it's life, who would have thought that it would seal up in other positions?

Brian