Yes Den-Den, you are right. They're air operated, we have checked for leakes and didn't find any. Those valves I speak off with the caps, I'm assuming those are the solenoid valves. There is a total of 17. We have stripped the drill head down, we didn't clean each of the valves, but I'm thinking it something we should do.

The valves have caps on the top which screw on and act as breathers... a couple of weeks ago one of those caps popped off and is missing. It may of got some dirt down in it after. Right now we have used the red green trick. (duct tape) over the top. But I don't think it's allowing the breathing to work right.

Any other ideas??

Thx