98 kenworth fan clutch sticking

Hope everyone is good. I am having an issue that I cant figure out. Been doing some research and nothing. My truck is a 98 kenworth T600 3406e. I have a Horton fan clutch (less then 6months old) it’s the older style one that is normally released and engages with air. It’s working when on but when I turn the fan off it doesn’t disengage completely. It’s partially engaged even with no air. I tapped the top of it with a hammer and then it disengaged. Any ideas. I thought to spray some wd40 into the air line? I got my air hose and blew me air thru it but continues to do the same thing. Any ideas. Don’t really want to pull it apart until I get home next week.

 

Yeah that’s what I thought about spraying some wd in the air line. Thanks for the response. I am on the road until next Thursday so I don’t really want to pull it apart until I am home. It is working just. Worst would be that it wouldn’t engage I guess.