What cause a car to overheat at idle?

Answer:
There are many possibilities for this to happen. Here are just a few:

1 - Clogged radiator
2 - A possible leak in the hose
3 - Low on coolant
4- Cooling fan may not be working
5- Defective radiator cap
6. Stuck Thermostat
7. Blown head gasket

If it only overheats at idle and there is no apparent leak and you are not loosing coolant my guess would be the cooling fan is not working. May be a simple blown fuse, defective thermal relay, or a defective cooling fan.
Contributor: Clay
First answer by Cooter pigpusher2009. Last edit by Baldfatguy. Contributor trust: 2032 [recommend contributor recommended]. Question popularity: 1 [recommend question].