Where could engine coolant be going if it is losing it but not showing up on the floor?

Answer 1

Do you see excessive steam coming out the tail pipe? Is there foam on the bottom of your oil fill cap or is there any sign of coolant on your oil dipstick? Any or all of these would indicate a blown/cracked headgasket. Have seen this too many times, typically when a car overheats once or more. Some engines are more prone than others for blowing head gaskets when they overheat just once. Check for the above first (most common). How much are you losing? I haven't noticed any of those signs. It is a low-milage Tahoe and has the Dex Cool coolant in it. I have recently been told that this "corrodes" the intake manifold gasket. But...it isn't showing any of the classic signs. I usually have to fill up the overflow tank (to above the hot line) every month. The oil looks normal, and it runs well. The only symptom is the rapid loss of coolant. I am at a loss as to what to do with it. If it is the head gasket the problem will worsen over time and become noticeable. Try replacing the radiator cap, when it goes bad pressure is released from the radiator before the correct pressure is attained usually blowing steam into the overflow tank and either overflowing it or boiling it away.