Citroen Xsara Picasso Stays up, it is covered

After a great Ayasco, the radiator temperature rose (the thermometers in Seville marked 43 degrees). After a while, already outside the traffic jam he was falling apart as if he were stolen, but with the inertia he could get to start. Apparently this symptom appears when it is excessively hot, according to my little understand. What could be, please?