2000 malibu overheating stumped

I have a 2000 malibu that is over heating. Here is everything I have done. Replaced the thermostate. Replaced lower intake gaskets. Replaced the water pump. I filled it up with coolant and moved it forward to see if it was leeking. When the resavoir was full it was boiling right out of the resavoir so I filled it and put the cap back on so I could let it sit to check it for leaks later. When I checked it later I noticed that there was no puddles under the vehicle and the coolant in the resavoir was completely gone. It is going somewhere just not sure where. I checked the oil level and it is normal and there is no water in the oil so I think I can rule out a cracked head but not sure. Also I noticed that the previous owners used bar stop leak in the resavoir. I really am stumped. Does anyone have any ideas? Thank you very much for any advice. Motor is the 3.1

*bump*

your cooling system know has air in and will need to purged. There is a bleed screw on the small line running over to the reservoir. Are your cooling fans coming on? Also check your radiator cap it will cause one to run hot.

good luck, Kenny

Sounds lkike your radiator is clogged from the stop leak. Never use that stuff because all you are doing is covering up and masking the problem. Usdually when it booils over, it is the radiator or radiator cap. If you have air in the system, you can bleed it like the previous post, but your bet is the rad. Go to a pick a part junk yard and buy a replacement from a car that shows signs of damage from an accident.