Hello all, it is a Colt 2007, 1.3 petrol with disc brake at the rear. At the back left the TÜV tester criticized the carrying image. I first tried to vent the brake and did 30 pumping operations with a helper and accordingly the nipple 30 times open and turned on. It only hissssss and hardly a drop of brake fluid comes out there. There seems to be an incredible amount of air in there. The other three brakes were good, there almost no air came out. We didn’t do anything wrong when venting, we already did it on some vehicles. However, I read that sometimes it shouldn’t work so easily with vehicles with ABS. Do I have to pay attention to something? Or did I have too little patience and we just have to try it for longer? The liquid level in the tank went down a little after all. Did the venting then stop first. Furthermore, the upper guide bolt is fixed, which is now turning at least, The bolts must definitely be new and I hope I can just get them out like that. Maybe someone has a tip. But my main question is: How could so much air get into the system? The caliper looks good, the hose looks good, too. Everything is dry, and the piston is flashy under the cuff. Or did it come through excessive heat from the solid guide bolt, that then such a huge amount of air will arise there at e twas older brake fluid? By the way, this was still quite bright everywhere. Would that only have liked to have clarified in order to find the possible cause and not only to repair.