04 International 9400i Secondary Tank Losing Air

Hard to believe (ie. very unusual) that it had 2 new compressors, dryers, & governors all within the past year.
The air dryer should not be leaking down for 10-15 minutes, after shutdown, as you say. That's #1 problem.
Also, coming down from 120 psi, the compressor should kick in lower than 110 psi (such as 90-100 psi). That would be a governor issue.

Have you also run a basic pre-trip air systems check? Also, does it leak down much more with a trailer hooked up?

 

I drove an '07 with similar problem. Mine ended up being the foot brake valve. I had just been assigned the truck and there was so much water in the system it mucked up the valve. Apparently the previous driver never drained the tanks. (No auto drains).

 

yup, my truck is doing the same thing. put a new governor and dryer on it, still doing it. I'm not making any friends with the air popping off every 30 seconds while idling. I guess next step is replacing air lines from compressor to dryer and air tank. gotta be a leak there even if we can't find it with soapy water.

 

If you air is popping off every 30 seconds, you may have a bad pressure release valve on the compressor. Once they pop, they usually need to be replaced.

 

Depends. Are you looking to see exactly *where* it's leaking from on the air dryer?
Could be just a bad purge valve, bad o-ring, etc, etc.

Also check for air bypassing the check valves, both before the primary tank, and the one between the primary and secondary tank.
Air should only pass in one direction. From compressor to the primary tank, primary to secondary tank, but not backwards.

 

this is what mines was doing... then it progressed to both tanks doing it. Found out it was the connector on the bottom of the turbo actuator valve control box thingy under the compressor(not sure what it's called but I do know it cost $800). I noticed that the air line fed into this looked kinked at the tractor protection valve, but wasn't leaking.... I spent the $0.65 a foot for a new line and started changing out the line. when I started to remove the old line I noticed the fitting was spinning and I almost dismissed this as it was supposed to do that... I looked closely and noticed it was threaded into the control valve so I checked to see if it would tighten up and it did. I tightened it down with a wrench and replaced the air line. So far since doing this (4 days) I've had no air lose, drove over 2100 miles in temps from 45 degrees to -1 degrees, elevation from sea level to 8700 feet.

also since tightening up this fitting, I have almost no water accumulation in my wet tank or secondary tank

Cummins ISX 2006 engine
2007 Int 9400i

 

have you checked the air tank itself for leaks? tanks rust from the inside out.