Continuous air leak from air dryer purge valve

I also spoke with one of the techs while I was there. He said he has seen a few do what mine is doing. He recommended that I change the cartridges and the governor. Full cartridges can cause the leak, and he's seen the governor cause problems too. I already have the cartridges so $16 for the governor...I'll see what happens

 

Thanks, now I understand. I sprayed the fittings checking for leaks, when I go back under there, I'll spray the whole thing. Good tip, Thanks

 

I did change the governor and it made a big difference. No more leak from dryer when engine is off. Truck sat for thirty hours and lost down to just under 60 psi. I think it still leaks somtimes when engine is running, but it does not seem to effect maintaining pressure, as it did before the governor change. I'm waiting on a good quality chain wrench to change the dryer filters. I ordered one, should be in any day now. I let you know how it does when I change the filters.

 

Thanks for the link for the filter wrench.
My dryer is a Wabco brand. In the manual they state that on most Cummins engines, the compressor gets its intake air from the pressure side of the turbo. There is a turbo cutout valve that prevents turbo pressure from leaking out of the dryer. Have you checked this on yours?

 

Well, I finally got the problem cartridge off yesterday. (mine is the twin cartridge type) I don't think that one had ever been replaced. When I got it off, it was filled with sludge. The bad part is when I unscrewed it, the nipple that the cartridge screws on, came out on the cartridge, and I can't get it out without ruining the threads. Under this part was filled with dry rust flakes. It has an electric solenoid which moves a piston back and forth to switch between the cartridges. This piston doesn't move; either because of the rust or the solenoid is bad. (I think the latter) I really believe the dryer is shot. Volvo dealer wants 2k for a new one, Meritor wants nearly twice as much. The cheapest parts I found to rebuild it was a little less than 1k, from Meritor they are twice as much. So I'm going to switch to a single cartridge type. The System Saver 1200 or the 1800 will plumb in with little modification. But I will have to plumb in a pressure controlled check valve at one of the supply tanks to allow back flow to regen the cartridge.
I guess I will do this doing the "sweep" next week. No need to go out and get put out of service. I'll post how it goes, and ask for help here if I need it. Thanks for the tips so far.