1997 Firebird V6 Going through coolant. No leaks found . Please help

Ive got a 97 firebird V6 3800 and i have to add antifreeze to the radiator every other day or it runs hot. There is coolant in the overflow tank, but its not being pulled into the radiator when things get hot. I did notice when i fill up the radiator it will push some into the overflow tank so i know its not clogged. I have checked everywhere and nothing is leaking. The ground is bone dry under the car. I also checked the oil for signs of antifreeze and checked the radiator for signs of oil. Everything looked good so the head gasket is good. Also ran the car down the road and had my wife follow me down the road to see if the car had white smoke coming out the back... nothing. any ideas would be greatly appreciated

thank you

Jeff

Ok i have been reading for the last 4 hours on this and im wondering if its something so simple Im just missing it. According to several sites, when your overflow tank continues to fill up, and your radiator continues to drop its coolant level, the culprit is something as simple as the !@#$ radiator cap itself. there is a seal on it that is supposed to open and close to allow coolant to pass into the overflow tank. if it fails, then coolant is now stuck in the overflow tank leaving your radiator coolant level low. saying i cant find any antifreeze anywhere on or under the car, and my overflow tank is now completely FULL, it makes some sense that the radiator cap may possibly have failed. Any comments or thoughts on this

thank you

dumb question, for those of you with the 3800... what is the rating on your radiator cap? as in 15lbs 18lbs.... can someone go check?

Yup, that's it. Faulty cap, same thing happened to me and I too was going insane. Changed the cap and it fixed it.......... well, I still have to add water/coolant now and then but that's because I was cheap and got "a" cap, probably not the right one, but I got it. And as far as the pressure on the cap, can't help you there, but I know is not the right one on the cap I got either.

I've had the same issue with my '90 3.1L EFI.

Found a very small coolant leak at the back of the block where a housing had corroded, though it only forms a drop or two when idling in gear for more than 5 minutes. Haven't replaced it, and it has held steady for the last two years. (Honestly, how often do you idle in gear for more than 5 minutes?)

However, my mechanic took one look at my radiator cap and told me that it was both in need of replacement, and the wrong one! Apparently I had a 12 PSI cap installed, instead of the 15 PSI cap that's required, causing the system to backflow from the radiator into the overflow after the engine was turned off hot.

Best of luck, and keep us updated. :)

Mine is doing the same thing.. I'll replace as its a cheap fix. Got a mess in the radiator after I over heated the system... Will have to do a good flush .. maybe twice to get the stuff a flowin...