Leaking Coolant?

About a month ago I was sitting under a shade tree eating my lunch in my 2000 Runner. I left the engine running with the AC on because this Texas heat is stupid this year. As I was leaving, I noticed the temp gauge was reading hot. I limped my way to a close Autozone and let things cool down. The reservoir was empty and there was no coolant that I could see in the radiator. I bought some AutoZone brand premix green and filled the radiator and reservoir. I have been monitoring the reservoir levels and every few days I have to top it off. I am not seeing any spotting on the ground. And I have looked all over directly after driving for any sign of liquid leaks. I am losing it somewhere but have no clue. Any ideas?

 

Couple of things.

Never mix green with the pink stuff.

Did you check your oil? Ensure your oil doesn't have coolant in it, which would mean headgasket failure.

Check your tailpipe, any white smoke? Does it smell sweet? This could mean you're burning coolant which goes back to the above.

If you see no leaks, no coolant in your oil, and you're not burning it off, check at the rear of the motor as you could have a leak (and coolant is being caught elsewhere) at your freeze plugs.

 

An easy check for a head gasket leak - any auto parts store has a product that can be put in the radiator (with the engine cool enough to safely remove the radiator cap) that will turn color if exhaust gas is detected in the coolant.

 

Like above mentioned, .... look at your coolant over flow bottle (when it has coolant/water in it) while idling, do you see bubbles?

If your loosing coolant, but arent cleaning the spot off your car port, you may have the dreaded blown head gasket. Its odd you don't have a dash light, usually for a mis-fire on a cylinder or the like.