Overheating while ac is on in traffic

My 2000 i30 overheats when I'm idling or in traffic after I've been driving for a while. When I first start driving it doesn't happen only when the engine has been running for a while, but if I leave the ac off it won't overheat. I hear humming sound almost light grinding sound and the reservoir tank seems to leak the anti freeze when it starts to overheat, I also noticed the ac feel warm as the gage was climbing so I leave it off. I've flushed the radiator and have a thermostat that I have to install but before I break the bank and go crazy on parts can you guys give me some ideas or pointers on dealing with this. Thank you for ur help