Air Pressure Drops when parked - Wanting to find check valves

[neoneddy]

I've done my due diligence here and found the manual.  Here http://busconversion101.com/PDF_Files/MCI%209%20Maint%20Manual%20in%20PDF%20format/MC-9%20-%20Maint%20Manual%20Section%204.pdf

Problem is the main diagram  is too blurry to actually read.  Can anyone point me in the right direction for of the main check valves to find and look at?

I think most of our busses lose pressure over time, but I know mine has gotten worse over the summer.  The gauge used to stay at 60 psi over night, now it's at 30 or less.   I still hear this buzzing  almost a hum from the rear end, I'd like to track that down.  I suspect it's a diaphragm or something fluttering as air is flowing the wrong direction.  No hissing from my air bags, I'm sure they leak too, but anyway.  Any tips on this hunt would be great.

[Oonrahnjay]

     Sorry to be no help, Shawn, but I blew up the PDF up to 500% and checked the clarity at each step.  You can gain a tiny bit of readability at moderate blow-up sizes but it appears that some of the annotations are basically more unclear than others and most of them cannot be read or even guessed at at any size.  Of course, once they're expanded over a certain "sweet spot", they get even harder to read as they're just broken down into a mass of pixels.
     I'm afraid you'll have to find a chart somewhere else (or maybe someone else here has one that they can send you by email attachment).

     Good luck.

(PS  I'm guessing that when you can get under it -- safely -- you'll find a relay or release valve that's leaking; probably a diaphragm, as you said.  I'm going to guess that check valves are not a factor here, but that's just a WAIG on my part.)

[gumpy]

Have you tried some soapy water in a spray bottle? 

[neoneddy]

I'm not sure where to even spray yet :-)   That's  primarily what  I need help with.

[buswarrior]

All the valving are consumables.

Any valve that is both pressurized and capable of releasing air to atmosphere is a first line suspect. So, the treadle valve, the rear relay valve, the suspension leveling valves.

Any pneumatic controls in the engine room are always suspects, shutters, damper doors, air tensioners, engine shut down plungers, etc.

Once you find a good one, get a copy of the air schematic copied specifically to write on it the last known change out of each valve. As you work your way thru, there are less and less untouched parts.

You WILL FORGET which year/decade you did something, believe me, I used to be smart, ain't so much anymore.

Defend against the degradation, WRITE STUFF DOWN!

happy coaching!
buswarrior

[gumpy]

What BW said.

Additionally, all hoses are suspect. Especially the braided ones. Spray the entire length of hose. The air bags are prone to develop cracks where they fold, and the seals around the upper and lower plates can leak. Even the saddle bolts can leak. Spray the air beams, especially at the top and any visible weld. The leveler valves are also prone to leak though those more difficult because it's usually internal and the air comes out the exhaust port. 

the buzzing you hear is air coming through the system to replace air that is leaking someplace.