Engine is overheating in traffic?

Once in awhile, more then I would like, my truck listed above overheats. I replaced the radiator, thermostat, water pump, clutch fan. The problem is the radiator overflow tank fills with with antifreeze from the radiator. But it doesn't drain back to the radiator. The overflow tank can fit almost a gallon, so as I drive the truck overheats because the radiator is low on water. So I have to add more water to the radiator and siphon out the water in the overflow. I tried bleeding the air out of the system several times already. It would work fine for a little while then overheat once again. I am at my wits end.

Ive got a 1998 ford ranger 4x4. When I put it in drive it overheats fast and then when I put it in neutral it wont overheat! Ive changed the termastat and the radiator and hoses what could it be?