I've been trying to get around to doing a full drain and refill of coolant on the '04 Disco. I don't think there is any problem, it's just that over the last two years it has gotten a bit old and it must be slowly leaking out someplace because now the level at cold is at about the 1/4 full on the overflow tank. I don't think it ever got fully filled last time, and it has slowly gotten down to this point over the two year period. So now I'm out of time, I'm going on a big road trip in two days. It does not run hot, always stays between 198-206 F. I have no reason to believe there is any "problem" with the cooling system.

Am I OK topping off with distilled water for the next few weeks till I get a chance to do the flush and refill?