Trailer air leak

The line could be leaking from either side. Cap off one and see if it still leaks. The side that's leaking, pull the hub cap, sometimes the line is just loose. If not, you have to replace the line.

 

Swivels where the inside line connects to the hubcaps were the culprit on one of mine. Two were leaking so I put on a set of new ones. those were the ones the trailer came with new, so figured the remaining two weren't far behind. The inside hoses are stainless wrapped and sturdy. Short of a buggered/loose fitting or seized swivel, unlikely in my opinion (but not impossible). I bought a new one just in case, and it's still sitting in my pile of spare parts. If you recently had a leaky hub seal fixed, the quality of the reassembly might be suspect.

Speaking of which, I recently pulled all the hubs on one of my trailers that had wonky tire wear on one end from loose bearings. I found a lot more than that, done by "service professionals" over the years, when needed on the road. Quality of the repairs fell short in nearly every case. Fresh semi-fluid grease and seals, and perfect preload using a DrPreload tool, and the trailer pulls smoother than it did when new, and I picked up around 3/10 mpg as a bonus.

 

Does any shops do the Dr Preload set up? I dont think I would want to buy the tool to do one truck and trailer.

 

The short hose is just a vent.
If air is coming out of that then either the swivel (as mentioned) at the inside end of the hub is leaking. Or the line attached to the other side of that fitting with the plastic loom going to the swivel is leaking.

 

There are a few, I'm just not sure of any. There's some discussions in the FB 9+ mpg group that refer to some. Come to think of it one might be near you in KC. I just never considered it because the cost of doing it that way always exceeded the cost + time of just buying the tool and their spindle nuts, plus the peace of mind having done it myself. I also have two matching trucks and trailers, so that helps justify it too.

 

I’ll check the group