Cooling problem with V6 3.2 ???

Hello, since I had my head seals done on my Omega now is the following problem, which does not want me in the head. I took the car on Friday from the workshop, on the WE hardly driven, Monday then with to work 35 back to and 35 km no problems with the temperature. Tuesday to work again, without problems in the afternoon back again, but bought in between, stood on the way to a few traffic lights, then drive on to the parking lot of the shopping center, I remember on a call, stopped to make a phone call, but let the car continue running and in the conversation the car went out, I had not noticed at all, only when I closed the phone, thought funny why is it off, I tried to start it, I didn’t then look why and look, the temperature on stop red, OK I waited for ADAC to bring the car to the workshop, It was about 45 min. When the ADAC then there was temperature down and he Spran g on, but for safety I had the car brought to the workshop, which took a look at the car Mittwoh in the morning, the temperature problem was not, in the afternoon another 40-50 km test run, during the test drive also nothing, then put in front of the workshop and let run a short time later and give three to four gassed and within 3-4 sec, the temperature curled up, so since the error was so striking, the temperature switch was ordered, then unfortunately came only Thursday, which tested the built-in, Thursday and Friday, temperature OK, then tested on Saturday, there came the problem again, now they still want to suck the WAPU and exchange the thermostat, but you are not good hope, because the error is so funny, as the temperature rises so quickly. Has VIELLET ONE SO A PROBLEM OF SCHONMAL HAVED ??????????????????????????????????????