well, i did some testing. and here is what happend!
i started the engine, started the fan, and then the klimatecontroller.
it was after that the leakage started and if turn off everything it leaks a little bit more untill it stops. i think the leakage might be after some kind of cock valve.
and btw how much work do you guys think it will be for me to acces this stuff, and should i acces it from the inside? there is no way to access it from the outside without lifting the engine out.