hi, I have problems with the coolant level again. container is filled up until the mark is finished. during the trip, the k.-medium is sucked out of the container until the sensor detects too little k.-medium. if the container is opened when the engine is running, then I can safely refill natural water. if the motor is switched off and the tank is opened, then the water from the engine runs back into the tank. I last had this error with my urla Subsdrive 2005. At that time the heating lock valve had also said goodbye. back at home I was told that the cooler is clogged, so it is renewed. now it is time for a holiday again and the error occurs again. I visited two workshops today: 1. workshop: cause can be a clogged heater, or air in the system. also the cylinder head seal was checked and the system tested for tightness. to further limit the error I have another new one. the workshop was then still that the water level in the tank with increasing temperature of the water had to rise. I am supposed to observe the matter further. 2. workshop: heating cooler has nothing to do with the matter, I should fill water up just above the tank marking. it was said that with increasing temperature of the water level in the tank falls, since the water is compressed (What is bought? my question is now, it will be more or less. heating cooler yes or no. how can you check something. does someone have another idea? in etzold there is more. oh so, car has run an automatic climate control system, 8 years old, 120 000. unfortunately, I couldn’t test the new container cover yet, berlin is full of fans, it’s just a start. many thanks in advance.