Ford Repair: overheating, head gasket problem, ford mustang

Question
I have a 1997 Ford Mustang,3.8.L V6 85,000miles
I've put in new the following:

Thermostat
Temp. sending unit
Water Pump

I've flushed the radiator and the block and checked all hose's.

I have found no leaks.

It runs good and cool at an idle but when I drive it it overheats.

Any help and advice would be greatly apprecaited..

Don't have any idea what else it could be.

Thanks.  

Answer
3.8 engines are notorious for leaking headgaskets the reason i think is because each head only has eight bolts and they aren't space from top to bottom evenly-i am sure there are hundreds of thoughts on the subject but that is mine.

you don't have to have steam out exhaust during first stages of failure-it don't have to skip at first or have water in oil but all this will happen eventually-verify head gasket problem then replace them and while your at it replace timing cover gasket also another weak spot with these vehicles other than that besides the rattling as they age they are good cars.

good luck.