z6 stock engine car doesnt smoke fan spins perfectlly thermostat opens too, using only water to cool it. runs perfect in the city but u cant go faster then 45 mph in the highway... the more u accelerate the more it heats up.. water bolis in the reservoir but. after it cools down no water is missing in the radiator!!

 

How old is the radiator? Could be internally corroded, especially if you've been using straight water for any length of time.

 

its not that old.. aluminum core.. its been using water for 4 months.. now i jumped the fan.. and it stils overheats in the hw..:S