well how much time for bubbles to appear?i ve this problem for over 6 months.never went beyond 5km. luckily my work place and all utilities r within this area. if i need to go far i use a cab or call a friend. i totally agree with your opinion of fully opened thermostat is like there is none when engine is hot.there r water drops from exhaust in morning briefly after starting i think which is normal. i was just telling what people do.by the way is there any special way of bleeding the cooling system other than pinching of upper hose 2-3 time after fill up.presence of air in liquid is one of the commonest cause of poor flow.