I've been searching this post for half an hour, but found it. In light of my interest in construction, I suddenly remembered this post and searched the forum.
Seems A long time ago that last post, time flies.
Check noodwachter72 on youtube, he also found a way to make the cabin of the excavator turn...brilliant!
I have to try and make this too, I guess you just have to put the syringes in the right place put in some water and with a tube you can pump the water in an out using another syringe or some other "pump".