I was always taught that after a suitable number of years, between 3 and 5, depending on who was administering the lecture, you should routinely change the CTS and the stat as, even if they are working, they may be deteriorating slowly and the ECU will be getting dud data and having to work with the stat sabotaging the cooling system. On another make of car I failed to change the CTS and little by little the engine began to misbehave at particular running temperatures. When the CTS was renewed the engine not only behaved itself but I suddenly found a lot more power available that I hadn't noticed that I had been slowly losing. All that bothered me from the OP was that changing the two cost him £560! Are these Volvo parts made of solid gold and fitted by the crowned heads of Europe?
