Trailer suspension issue

Is the port circled supposed to have air coming from it at all times or is it supposed to be an exhaust?

Its on a manac stretch trailer with a lift axle that I bought. There is a petcock on the end of the hose and the fitting leaks constantly.

My leveling valve was leaking from the exhaust so I changed it and its still doing the same, wondering if this valve is bad and causing the leveling valve to leak.

 

Yes the new one is leaking also.
I adjusted it and it stopped for a while but then it will start letting air out of the exhaust again.

I'm also trying to find out about the valve block pictured to know if I need to plug that line to stop it from leaking or if its supposed to be an exhaust and it is stuck open and the previous owner out a petcock valve to stop the leak in error

 

Its an 08.

Of course the exhaust port shouldn't be plugged, but the problem is, I dont know if it is an exhaust port or not. There are no markings and Google hasn't been much help.

The end of the hose connected to that port has a push fitting with a petcock on it like the ones used to drain an air tank.

 

Yes I know that much.

Just can't find any diagram or info pointing to which port does what so I can see if its an exhaust port or not

 

Would anything else cause the leveling valve to constantly leak from the exhaust other than the valve being bad??

 

So I traded to see where this valve comes and goes.



The line circled in red, comes from the air bag side of the leveling valve
The line in yellow goes to the bags.
The blue circled line goes to a valve coming off the air tank.

The purple one hangs down and has the push fitting with the petcock on it. Pictured below.




Below is a picture of where the blue circled line goes, which I believe is the signal line for the valve


Anyone know yhe reason for this valve?