empty overflow tank problem

[melloD]

i flushed my radiator when i realized this oily substance in it. i refilled both radiator and overflow tank with strictly coolant and after driving about 6-10 or so mile for the day it the overflow tank reaches minimum from max. i would really like to know whats goin on here. it a ga15de i need some help on this

[nametakennow]

I'd start by looking for a puddle, then checking around spot of the puddle for leaks.

However, you said there's an oily substance. You could have a much scarier problem. Your oil may be mixing in with your coolant and vice-versa. Coolant doesn't make a good lube. I'd check your overflow tank and take a closer look at the substance, if you think it may be motor oil, change the oil and see if there's coolant in it.

FYI: Don't run on 100% coolant, you definitely need some water in there. Keep it between 50% and 70% coolant and the rest water.