Need some advice. I have been trying to find a air leak when the bus is sitting brakes set or not doesn't matter she will drop air pressure from 120 to 60 psi in about a half hour but I can't find it. I have listened in the tunnel, audible air movement through the tanks, sprayed soapy water on the fittings and lines found a few small leaks and fixed them but no change You would think you could hear air movement but nothing. Maybe the one way check valve to the compressor? I haven't checked that yet its hard to get too.
For back feed through the compressor, stick your ear into the air filter housing.
I hate using tools before I have to...
No air suspension added to that one?
How much air controlled stuff in engine room?
Exhausts bleeding on the relay valves?
Rust on the air tanks?
Keep looking the easy way, tools just make more trouble to add to the trouble you already have...
Happy coaching!
Buswarrior
You could undo a connection somewhere, ideally put an air fitting and pressure gauge on each side, and pump up each side to pressure. That can help you narrow it down if done smartly. Repeat as necessary.
Ok. Check valve from the wet tank to the air dryer is working. However the check valve between the wet tank and reservoir isn't I will fix it but that shouldn't drain it all down right. I will try your ideas also thanks.
Mci? Year?
His title says, "1968 Eagle 05"
looked in usual places and didnt see it.
check your air tanks. Of that age, may have some pinholes. Easiest to supply air from a source not of engine and distant enough not to drown out leak noises. Nu Calgon 4122-84 spray leak detector works great. Amazon.
Just found a big leak it was a aeroquip line from the skinner valve to the fuel shut down you couldn't hear anything (maybe I'm getting deaf in my old age) until I sprayed it with soapy water than it sounded like frying bacon the whole line foamed up. Rear tanks,lines and valve were fine I'll check the front another day. Thanks for the help.
I was just about to suggest the Skinner valve area. Don't forget to check the lines from the other Skinner to the fast idle cylinder.
I did and a few others. I need to change the fuel lines too hard as a rock aeroquip that looks like a p.i.t.a they disappear into the obis.
I had trouble with the return line leaking badly, suddenly. They connect to the top of the driver side tank. Hopefully, the floor above it is not covered with permanent structures. As I recall, in a seated bus the access was through the return air vent under the seats.
Eagles came with automatic drains they leak and are hard to detect
DoubleEagle the return is under the vent door but I can get at it between the tank and floor same as the draw line other side crowsfoot will work if all else fails. Clifford no auto drains here only pull cables.
Whether they are auto drains or manual pull cable, they can both leak a little or a lot.
Had a manual pull cable type develop a pin hole in the ball area on our 4104.
We have a couple manual pull valves on our 4104 & have to yank them multiple times to stop them from leaking - they're a PITA. Actually since we installed the drier we hardly ever pull them & when we do - nothing - but they still want to leak...
Well 24 hours after I changed the Aeroquip line that was leaking and aired it up I have 85 psi left pretty happy with that, still have to check the front air system. lesson learned as many times my head was right next to that line I never heard a sound and assumed it wasn't leaking.
I was a mechanic for a big city fire department for 30 years. You cannot have leaky air systems on fire trucks. If there is a leak it will turn up with soapy water. If it is a big leak on a large component, like the air compressor air intake, I put my fingers over that area and spray it down to make it easy for bubbles to form. If you think a component can't be leaking and you are still searching, spray that component. I have found air tanks with pinholes and fittings that need U-joints and crowsfeet wrenches to tighten. Don't give up easy. Be suspect of every part of the air system.