Renault Rapid Temperature Problem

Hello all, I’m totally new here and very curious who will answer that way. My problem is our Renault Rapid Bj. 97, petrol. At first the car ran quite well but now – it goes off with the repairs violently. Without notice the temaratur rose and the Rapid began to smoke. Diagnosis – head gasket and crackers were there. Was repaired – car did not run. Diagnosis – water pump – was repaired and car drives about 5 KM and then the engine gets really hot and sp The cooler is cold, cooling system has enough water. I have now got the tip that the thermostat is defective. Can this be and where can I find this part? What can have been broken and where can you get detailed information about the Rapid in the Internet?