1968 Eagle 05 undetectable air leak

[tr206]

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.

[buswarrior]

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

[hogi6123]

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.

[tr206]

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.

[chessie4905]

Mci? Year?

[usbusin]

His title says, "1968 Eagle 05"

[chessie4905]

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.

[tr206]

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.

[DoubleEagle]

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.

[tr206]

 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.

[DoubleEagle]

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.

[luvrbus]

Eagles came with automatic drains they leak and are hard to detect

[tr206]

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.

[DoubleEagle]

Whether they are auto drains or manual pull cable, they can both leak a little or a lot.

[chessie4905]

Had a manual pull cable type develop a pin hole in the ball area on our 4104.