as triathlete said.. if there is 100% antifreeze in the radiator, that probably accounts for some of your problem.. antifreeze doesnt cool your engine that well, the water mixed in does most of the cooling.

a 50/50 mix of antifreeze (ethylene glycol) and water has the ability to absorb about 33% more heat than just straight antifreeze at 160ºF

antifreeze lowers the freezing temperature, raises the boiling temperature, and has additives to prevent corrosion of aluminum radiators