So I'm new here, sorry if I'm not doing this right.
I have a 1998 Expedition XLT 5.4 2wd. Long story short I have a slow leak on the rear air bag suspension system that I can not find. It takes about two days of non use for it to be sitting near the ground. Here's the details.
I used soapy water on everything, numerous times and found nothing.
I replaced the air compressor a few years ago.
I cut power to the system for two days and it didn't drain!
Tested the relay, seems to work fine.
Control module and height sensor look fine.

So I replaced the solenoids, thinking that was the problem and it still drains...

any ideas???

I do not want to replace the rear bags with springs because I tow a large travel trailer often, and love how it self levels.

 

try fully inflating the bags and then leak test

 

Wouldn't those leak when I disconnected the electrical though?

 

missed that part of your post.

 

You may need to make up a line with a shut off valve and an air press gauge in it and insert that line between the compressor and the air bags. Once the pressure is reached close the valve to isolate the compressor from the rest of the system and just watch it. If the pressure holds you can be reasonably sure the problem is before the shut off valve. It's worth a shot.