Secondary air tank drains fast, but only on the highway

Brand new Cascadia. It doesn't drain when circling a parking lot, at that kind of slow speed. I can hear no leaks anywhere on truck and trailer when parked with the trailer brake released (air being supplied to trailer), or tractor brake.

Going down the highway, the secondary air tank (or both and it's not catching the primary guage?) will drain to 90 psi in about 20 seconds after the release valve pops. Compressor starts back up, cycle repeats.

Opened the hood on level ground, released all the brakes, pumped the air down with service brake till the compressor kicked in, kept hand under release valve to see if it just stayed open once it kicked out. Nope!

Any ideas? Would you just keep driving it like this as opposed to a shop repeatedly ####ing around with it, never finding anything through lots of downtime? Or as a company driver, being put into a loaner for an extended period of time that has more #### wrong with it than this new Cascadia?

This is so weird.

 

Truck did sit for an extended period of time. I cleared out a massive birds nest that was near the air dryer release valve.

Primary guage does go down for things like using the service brake. Just not during this weird highway leakage that comes without touching the brakes or shifting gears either (automatic transmission that I suppose uses some air)

 

Still haven't been able to switch trailers. Tried the trailers set with tractor released, did not notice any leaking. Which makes sense in that the tank doesn't drain till I'm going highway speeds. Seems to drain faster at 65 than 55

 

Thank you very much for all the replies from everyone, and especially to this one.

I checked my truck into the company shop today. Everyone at the shop today, and yesterday on the phone and at the shop on the road was like "that doesn't make any sense" and I half got the impression they thought I was ############. So I actually videoed it happening.

First thing tomorrow I'm going to tell the shop this suggestion. And half the reason I was asking was if people would still drive with it, because it was hell finally getting this new truck assigned after my older assignment kept falling apart from previous drivers beating it to hell (along with today's trucks being designed to be disposable). And I wanted to avoid a loaner because the loaners all have their own problems. But I just told dispatch I wanted to stay with this new truck after I limped it to the yard. I'll take unpaid time off if it comes down to it while they fix this one. Sick of trucks breaking down or being unsafe.