I've had issues with my 156 JTS cooling system the last months... It all started last autumn when engine was too cold all the time. Took it to service station and they replaced temp sensor, but after that the engine was too hot, so I had to replace thermostat. Service station only had a used one, but we tried it. Car worked perfectly for a short time before engine started to going to hot again. This time it was not that serious, so I could set fan heat to highest and engine would not overheat too soon.
I suspected the used thermostat, so I bought a new one for the mechanics to install. After that I couldn't even drive more that 5km before the engine overheated! The fans did not help so I went back to the service station and he could almost guarantee that it was the water pump failing because I had too bad water circulation and engine fan did not start.
So I got the waterpump and timing belt replaced but still something was wrong. Car overheated and engine fan still did not start. Mechanics connected computer and saw that the actual water temperature was 97C when in-car gauge said 125C! So computer or gauge is broken. But engine fan did not start until 105C and it turned out to be the 'slow mode' fan relay was broken. Now it's fixed, fan starts at 96C but only on fast mode. Now my car works really good and it's so nice to finally be able to drive it again. But in the beginning I was really worried about the temperature, as the gauge displays 125-130C all the time, and it's still annoying. So I'm wondering if anyone have had this problem? Is it the gauge or is it the 'computer' that sends the signal that is broken!?
Waterpump was in bad condition, engine fan relay was broken, the used thermostat was probably opening too soon so that I barely could make it with the in-car fan set to highest, and the temp sensors replaced twice. But all this time the gauge probably also displayed wrong temperature, so in fact the engine was too cold all the time and that could explain my much too high fuel comsumption.