[MJK]

The system was flushed but it didn't help at all. As mentionned previouly the car works fine without a thermostat (It is just to bad that I can't run the car without a thermostat).

I think you maybe right reguarding the water pump. I may have to replace it. Maybe the thermostat is creating enough restriction in the system to overheat. I don't think the head gasket is the problem because the oil is clean and there is no lost of coolant.
How big of a job if the water pump to replace. How long shoult it take?
I just can believe that a car with only 60K miles can have a problem that hard to figure out.