energie,
you do'nt say what stage you're at...but i assume only a few hours done.
i would'nt worry greatly at this stage about the plumbing...more important to get the checks right and understand what you are doing and why you are doing ithem..you can look at the plumbing later...the diagram is in the aircraft manual..
i also assume you are talking about calling your instructor after hours ...if so he's perfectly entitled to have a few drinks...
since i am assuming you are at an early atage i am therefore also assuming that you are not yet solo as you should certainly understand the checks and why you are doing them by then...but up to then it is a process of learning a little with each lesson...and that goes for the checks also but such things normally are introduced at an early stage under supervision...and with the later lessons you would normally be expected to do them yourself being monitored...
we used to do a more elaborate walk round even on days when the weather was bad and we could'nt fly...that gave plenty of time for questions...try that...go in on a bad day and spend time with the instructor on duty...
not knowing the full details of your relationship with your normal instructor i would'nt want to jump to conclusions...but if you are not getting good instruction or not clicking with a particular instructor...get another...or go to another school...
good luck.
the dean.