As a hydraulic instructor you run into all kinds of different concerns as you work with students, the biggest one is that of safety. Today we had to put the loader bucket back on a machine, it's an attachment with quick couplers and you can remove a few pins and drive out from underneath it. Well like i said we were putting it back on today and it has been outside in the sun and the oil had heated up and expanded enough to put pressure on the lines. One of the students said i can fix that and pushed the ball in with his thumb spraying him and everyone around as well. It was one of those moment where i was just to say stop when he did it anyway. Hydraulic injections are so very dangerous and this was no different, nothing seemed to happen but that's not to say that it couldn't as well. We all have to be careful when working around pressurized hydraulic systems.