Dear fellow tsikoteers, 'am just wondering what's the purpose of the coolant reservoir attached to the radiator? is it a holding container in case coolant overflows from the radiator? or it in case of overheating, the radiator sucks in the reserve coolant from the reservoir? can anyone enlighten me on this? add ko na rin, is it ok to top up pure coolant in case the level in the reservoir goes down? or it should be diluted with distilled water? Pardon for my ignorance, i've been longing to ask this. TIA