Have one EE-90 with me that stays with me just due to my affiliation to it, besides keeping other cars.
A similar problem occured last summer when it would spoil either of its cooling system parts one day or the other. First its radiator leaked, then the water body, then came the Hose pipe and then the radiator cap. The problem used to get more pronounced and frequent in the local run, however on the longer routes, it didn't bother me much. The mechanic everytime used to say that its due to overheating and used to advise me to hotwire the radiator fans. I never succumbed to his wish and kept investiagting it one way or the other.
One day while checking its auto electric fan switch and thermostat valve by placing a thermometer in water in a cooking pan alongside the thermostat valve and the switch hanging but immersed in water, with the switch wires out and attached to an ammeter to see that at what temperature the thermostat valve would open and at what temp would the fans switch activate.(Got the guidance from Reader's digest book 'Do It Youreself Manual')
I observed that the thermostat valve partially opened at 73'C and was completely open at 80'C whereas the fan switch activated at 96'C. This brought me to the conclusion that the fan switch was at fault as it should operate somewhere in the range of 82-85'C. As the ambient temperature for a common car is 82'C.Due to its delayed operation, the engine was getting over heated and parts of cooling system were being blown up one by one.
I changed the auto fan switch and since then i had no problem wahtsoever. everything including AC is doing perfectly fine.
Regarding your querry of coolant in the cooling system, let me add that the coolant in winters resist the phenomenon of freezing, in summers they are equally helpful as they have a higher boiling point than tap water and just in case your car overheats beyond 100'C. tap water would become steam, whereas the coolant would still remain in liquid form till the time their boiling point is not attained. Also they have anti rust quality and they protect the inner side of your cooling system from rust to keep it running for long. So i suggest you try a good quality long life coolant but only after your coolant reduction problem is solved.
Do check your AC compressor as they start putting lots of strain on engine if their bearing is worn out and you cant make it unless they start producing sounds.
Hope it helps.. Regards
