question on my air dryer on 93 harsco bmy m925?? stuck valve or leaking seal??

[hokie8358]

I just noticed on my 93 Harsco m925 cargo truck, that the rear air dryer was making a strange purging sound. after it reached 120 psi, and pop off valve blew down. started making a sound as if it was a compressor running. after that I climbed in cab and had a low air alarm and noticed secondary tanks down to 58 psi. I immediately climbed under truck toward rear axles and noticed just a slight few drips of water and a small continuous amount of air steadily leaking by. so I held my hand over opening and wow!! it sealed back!! no more leak. decided to take it down the road for a test run. once pressure was up to 120, it blew off again!!! whata ya know, leak was back!! same sound as before and low air again on secondary tank. truck has 6800 miles and I ve put 950 on it in last 4 months. with no issues! is this dryer need replacing or is it something I can fix or part to replace!!! when I blow down my tank valves, I never have any moisture come out. please someone let me know!!!! lol!! my first dance with this issue!! so kinda in the dark!! thanks

 

[hokie8358]

I just noticed helo's post on air dryer!!! mine is doing same thing!!! thanks very helpful!! guess its best to replace the whole unit!!

 

[wheelspinner]

Pull the purge valve off and clean it, grease it and put it back together. Including gathering tools, maybe a half hour job. Mine has been fine since I did that. No sense spending a bunch of bucks without trying the free and easy first.....

 

[helomech]

I pulled the bottom part of held in by three screws. Then I removed the C clip that holds in the valve. After that pull the valve out with pliers (it is not easy). Then I removed the screw, cleaned it up, put locktite on the screw and tightened it up real good. You can't tighten that screw until it is removed from the dryer. It just spins inside, you need to take it out to hold the backside from spinning. Mine seems to be doing great now, but will take a little road trip tomorrow to make sure.

 

[Coffey1]

Also change the filter dryer it may be saturated .