That Dreaded "hisssing" sound we all hear

[pgchin]

Ever shut your bird down after a great run in a WONDERFUL location, ready for that 5 o'clock beverage, only to hear that sound all air birders have come to hear and shutter at HISSSSSSSSSSSSSS?
Step1, 5 oclock now, fix tomorrow!!!!!!! The bird is nested!
Step 2, when you get around to it, the truth is it could be a thousand different things, lines fitting, etc. Here are some of the more common causes BUT the list is not all inclusive so please add to the thread for the benefit of all, thanks!!!!!
- if its'a mid 90-'s PT up through LX/LXI's then this may be the culprit:
http://www.ryderfleetproducts.com/ryder/...tDetail.do
pretty east to locate and fix, I always carry 2 spares. 4 total in the systems / birds described above. Only tough one is tucked up under the frame on the curb side of the air dryer....... 2 multi-line junctions plumbed to it, I cheated and just replaced the housing, spring and diaphragm! Always, always, always BLOCK the bird with MORE THAN 1 safety system before crawling under, like wood, HWH's AND jack stands..... redundancy is KEY!!!!!!!!!
- check the water closet clippard valves, those little buggers leak a TON of air when they get old, pull the panel out by removing 4 screws and inspect the lines and valves, sometimes a line gets jiggled loose and you can just push on the collar toward the valve to remove the line, make a fresh parallel cut in the line and push to reinstall the line. Clippar website here:
http://www.clippard.com/
- purge valve in the air dryer ( see air brake tip post)
- Engine air compressor or auxiliary bus compressor, lines and fittings causing a loss of air due to a malfunctioning check valve.
The best thing you can do is fire up the bird and see if it builds air and holds....if the engine compressor can keep up with the leak, then you can probably limp your way to a shop SLOWLY i you can't find it or need to, if it can't, then the brakes won't release and its time for a landoll Tow!!!!!