Air system problem

Are you pulling the same trailer a lot, or do you switch trailers all the time?

 

Went through about the same thing not to long ago. It started out that way very slow to build air would even lose air at idle with no apparent leaks. It turned out to be the turbo acctuator (ISX). Only would leak when the truck was running.

 

If you build up the air and release the brakes, then lower the pressure to 50 lbs, it must build up to 90 lbs in 3 minutes. It should do it in 2. You want to remove the compressor discharge line and as was said look and see if it is carbon-ed up. Remove the line from the dryer and see if it is restricted. If it is a Teflon hose it should release if removed and dent. If it is copper then you need to remove it and actually burn it out.
To test the system for leaks at the unloaders remove the air intake to the compressor and when the compressor is unloaded see if there is air leaking into the intake, depending on what compressor you have you could have a carbon-ed up valve that is not sealing or the plate could be broken.
Testing a compressor is best done with shop air, and a regulator.
Just a thought!

 

I am not an expert, but I would check the following:

Have you isolated the problem to the tractor or to a trailer?

Does it do this without a trailer attached?

Does it do this with every trailer you are hooked up to?

 

water in a tank maybe? sloshing? granted your supposed to bleed your tanks during the pti, but have you?

 

Yes, I ended up taking it to Volvo dealer they found it. They could activate it with the engine off so you could hear the leak.

 

Did you find your problem?