Air System creeps back down after buildup, HELP?!

Hi All,

I am struggling to solve an issue in my air system. My truck is a 2015 International ProStar with the Navistar N13 engine (mileage 536k).

When I start my truck up, it quickly builds up air pressure to my cutout (around 135-140 psi). However, it slowly creeps back down to 105-110 psi. This happens both when idling and when driving.

When idling, my truck will hold at the 105-110 psi range until I turn it off. If I turn it off then back on, it’ll build back up to the governor cut out then creep back down to 105-110 until I turn it off.

When driving if I use my brakes, my pressure will get down to 95-100 psi then immediately build back up to the 105-110 range. Occasionally while driving, it will get the pressure back up to the cut out and then slowly fall back down. If I pull over, turn the truck off, then turn it back on, it gets the pressure back up to the cutout before falling back down to the 105-110 range again.

I had my air dryer replaced yesterday. Prior to that, the truck wouldn’t build over 60 psi. I cannot hear any audible hissing sounds indicative of a leak, and the truck passes the air brakes test. The next step that I’m thinking I will take is to spray down the valves and connectors with soapy water to check for smaller leaks. Granted I have no experience in dealing with air leaks, it would strike me as odd that I would have a leak that could cause my pressure to drop 30ish psi and hold there yet at the same time it can also build up to the cutout.

Does anyone have an idea or a pointer as to what may be my problem? Thanks in advance for you help!

 

Thank you for the pointer! I will look into that

 

Thank you! I couldn’t find any leaks, although I didn’t see your message to check the hose from the compressor to the dryer until it was too dark. I will check that tomorrow.

It typically was taking about 15 mins to go from cut out down to 105-110. Oddly enough, I noticed today that it was maintaining 120-130. Maybe the new air dryer needed a bit of a break in period, or maybe I’m overly paranoid!