Secondary air pressure issues

Most trucks actually have 3 tanks. The wet tank is plumbed to receive air after the air dryer and supply air to the primary and secondary tanks. On most International 9000 series trucks you will only see two tanks. One tank is a combo wet and secondary tank with a wall welded in the middle of it to separate the two. There is no gauge for the wet tank. When air is compressed there is always moisture in it and other contaminants such as oil vapours from the compressor that the air dryer misses. The wet tank is used to allow those contaminates to condense and separate from the air so that only clean and dry air make it to the primary and secondary systems. On trucks the primary is identified by either "Primary", "P", "1", or the colour green. Secondary is "Secondary", "S", "2", or the colour orange.

 

Instead of soapy water in a spray bottle, I use a garden pump up sprayer.Saturate everything, inside frame rails, air bags, firewall everywhere.

 

Nothing special, those are just push-in quick connects. The line will not release if there is air pressure in it, so make sure all the air is out. At the end of the fitting is a brass collar. You need to get some pliers and rotate that collar back and forth to free it up, make sure the line stays still. It is sealed by an oring inside and you want to break the seal between the oring and the plastic line. Then you just need to push in the brass collar towards the fitting while pulling out the air line. They can be very stubborn to get out, so might have to try a combination of pushing the collar in while wiggling the line and twisting the collar. You almost need three hands for some of them, LOL!

 

I have been fighting the same issue, only happens when driving, the heavier the load the bigger the issue. The dealer has not been able to find the issue. Today I found a airbag leak but only at just the right height. will let you know if it cures my problem, might be the same in your case.

 

I have used PB blaster and WD-40 sprayed in connection to dissolve some of the dirt build up. Also I have pushed the air line in the same time pushing the collar in to loosen.
OP you can take those fittings off and put regular brass ferrule and barrel fittings in place. Most dealership/ parts houses have both styles.
Good luck.