MCT is green isn't it? You might just have a loose fitting or a real slow weepy leak on that fitting...The build up is probably from that....I know once my res plug was a little loose for a while and I got a blue build up on the top of my res on the inside around the plug hole.....I was using blue Pentosin is why mine was blue build up....
If its some kind of crud try using some of this in your loop its good stuff...
...PT Nuke
If its some kind of crud try using some of this in your loop its good stuff...
...PT Nuke