Hello and welcome to the forum. Where is McMasterville? Are you from France or maybe Belgium? It was interesting to check out the link and pictures.
When you post a reply, there is an icon in the tool bar for inserting pictures. You must have the pictures hosted on a server such as Flickr or Photobucket, then just hit the "insert image" icon and copy the url to the pics on the host server.
It's hard to tell much from the small pictures, but my best guess is that the pump is cavitating when you attempt to pump the near boiling wort. I would suggest using larger diameter hoses and keep them as short as you conveniently can. The boiling point is lower for hot wort subjected to suction and this can create vapor pockets which will interfere with the pump and may cause it to lose its prime. Small diameter hoses or restrictions at fittings can also cause cavitation. Often, it's a combination of wort temp, hose size, hose length and restrictions at fittings that cause problems.
May I ask why you want to pump from the boil kettle to the mash tun?
Tampon has an entirely different definition over here. I don't think we need to go there. I'll settle for the kettle that you keep your wort in while you sparge. Close enough!
From the looks of your brewery, you will fit right in here!