Need help with antifreeze leak

My antifreeze is leaking from my 2000 Trailblazer. Looking under the hood, there is seemingly a tank(perhaps it's part of the radiator), to the right of the radiator. It is rectangular in shape and has flanges(?) that stick out in a pattern going down. The antifreeze is collecting on those flanges and dripping. It seems to only be leaking when the air conditioning is on. Can anyone help diagnose my problem?

If you overfilled your cooling tank It could just be the expansion form the cooling system. Check the coolent leval in the tank when hot.

Welcome to the Forum!

Start here, read this thread carefully:

http://www.automotiveforums.com/vbulletin/showthread.php?t=729213

You are describing your Coolant overflow tank. It may be too full as taillight says or you could be overheating.

How much leakage are you seeing? drops? puddles?

How much coolant is in the tank when hot and also when cold?

Are you seeing the temperature gage on the dash going above 210° when the Air Conditioner is running?

When was the last time your system was serviced?