i know if water level become too low the car eventually become heat up and gasket will blow etc.current situation is after 1500Km the water level from reservoir water goes from full mark to minimum mark(about 180ml is leaked).Water level in radiator is still full.so its not that much serious.i know haldi will work(have experience:-)) but i don't know how it react with caltax coolant,i want to avoid any change in chemical characteristics of coolant.I'll try ur method first other wise i'll go for welding option.