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.
Could be a failed engine coolant temperature sensor. Easy enough to replace and not too expensive.
This sounds like bad news. The coolant could be leaking into your engine and mixing with the engine oil, then cooking off. A simple test can tell if there's water in your oil.
I would say that you are losing coolant somewhere hoses,water pump,radiator.
Sounds like engine coolant getting in crankcase, could be an intake gasket going bad.
The coolant temp. sensor could be bad....or the thermostat could be stuck shut.....there are a few things it could be actually
could have a crack in it that is leaking under pressure
If the coolant reservoir can not maintain the proper level of coolant, it is possible the engine could over heat when the level drops.
The coolant sensor moniters the coolant temperature. A faulty thermostat could cause the engine to run cool.
If you have coolant on the top of the engine it could be a leaky thermostat housing or a leaking intake gasket.
The coolant could have frozen in the radiator. If that happens the coolant in the engine will just get hotter. It could also be the thermostat.
There are ways to trace a leak. If you take it to a shop, they can mix in a dye with the coolant and after circulating a black light is used to find the leak. The dye only shows up under black light conditions. This is if you have a leak externally. If you are losing coolant internally, check your oil to see if it is foamy, or looks abnormal in any way. There are many coolant passages inside of an engine block and if one of the gaskets that seal it from leaking blows out or breaks, the coolant could be leaking internally into the engine. If you are losing coolant into the combustion chamber this is usually indicated by white smoke from your exhaust.
Your engine could be losing power and your check engine light coming on for many reasons. It could be your spark plugs needing to be changed. Your fuel pump or fuel filter could be clogged or starting to wear out, or your engine oil is to low.