What is wrong if you can smell antifreeze from the AC vents and the engine starts to overheat when stopped but goes back down when moving?

Check the floor on the pass side. It is probablly wet and the heater core is leaking. This is a pretty big job and if you want to change it your self, get a manual from the parts store or AUTOBOOKSONLINE.COM

Answer

Hate to tell you, but changing the heater core may get rid of the antifreeze smell from the vents, but it won't solve the overheating problem. You need a new fan clutch (if you have rear wheel drive). If you have front wheel drive, you probably need a new electric cooling fan or cooling fan motor.

It's pretty simple to understand. When you stop, the cooling fan comes on to pull more air through the radiator. When you start moving again, your speed forces air through.

It's a pretty simple fix, and for most cars should cost less than $150. You can get by with less than $75 if you do it yourself (unless you own a BMW like me--my fan clutch is $225).

Answer

I have the same issue, and the fans were not working. My pigtail was loose connected to the sensor, so it was just a bad electrical connection. However, now that my fans are working, its overheating dramatically!