I own a Fiat Linea diesel Emotion 2009. Radiator fan does not start even at mid temperature mark of gauge without AC. However, with AC on, radiator fan works. To my surprise, temperature needle stays at half mark even when coolant starts to boil and radiator fan doesn’t kick in without AC. To test, I accelerated roughly in city without AC to check the radiator fan kick in with rise in temperature which in no time rose to half mark but fan doesn’t kick in. I replaced the coolant temperature sensor with new one (Old one was also fine) and still fan doesn’t start without AC. Mechanic had put a candle light heat on the sensor when attached to a circuit, and the fan started without AC on. He’s of the opinion that the hot coolant might not be reaching the sensor due to bad thermostat valve and suggested full thermostat elbow replacement which included valve, temperature sensor and other minor components. Should i go for it ? Need guidance.