1. Thanks for the reply! Given the facts I listed in my prev. msg and namely the fact that it is not only a dash warning but also the symptom of warm air stopping to blow, could I then be sure that it is NOT a false/over-sensitive sensor and consider it to be an issue of a faulty thermostat?
2. It is not an issue of lack of coolant, cos I had the coolant changed half a year ago. Whether or not there's an air lock - I don't know. Gotta trust the mechanic who changed coolant or ask again for this to be inspected. The coolant tank shows that the coolant level is within the norms so that makes me rule out insufficient coolant being a cause for the problem (air lock could still be present though
). Well, all that leads me to think that the probable cause for the whole problem is a bad thermostat or possibly the pump, as you said, but I'm rather unaware of anything concerning the pump ... So, as you said, a test if the thermostat opens up when heated in boiling water will tell me if the thermostat is at fault. And if indeed it isn't expensive i'll just change it.