Hidden air leak

[acme66]

Trying to find a substantial air leak. From 130 psi to 30 psi in an hour. Already pressured the system externally and gone over everything with soap. Found a few little ones but even with those fixed the pressure is the same. Can't hear anything. Ideas as to what could leak that much but not bubble or hiss? Extra info: if it matters I get a strong whiff of gear oil each time I set the park brakes and the park brakes set quickly but hiss for 20 seconds or so and I can hear air flowing but not leaking under the dashboard when they do. On my phone sorry if awkward. Ken.

 

[MtnSnow]

Double check your brake pedal (the brake might be leaking internally thus why you do see anything with soap water). Also check the CTIS drier

 

[Swamp Donkey]

If the air solenoid on the transfer case leaks internally it can push gear oil into the air filter canister through the transfer case vent. The transfer case vents to the intake stack. When the parking brake is applied, and also vents to the intake stack, the smell is pushed out the top by the burst of air where you get a whiff. Check your air filter canister and I bet you find a puddle in there. This could also be your air leak you can't see or hear.

 

[Goobs]

These have more air leaks than Grandma.........

 

[Warthog]

Type of truck?

 

[Monstrosity]

I have a 84 M923 doing this same problem is there a way to clean this actuator or do I have to remove the transfer case and replace it?