Ok, in that case then it could be the water pump that is worn and has a poor performance or if the radiator fins are corroded, restrict the airflow and don't cool enough
Before getting the pump changed, carefully check your radiator and the A/C condenser in front of it. If the fins are either damaged or corroded it will reduce airflow. Be especially careful if your car has the old copper radiator (painted black fins) as they turn to dust.
The 2.5 came with a plastic impellor which is prone to cracking and then slipping at high engine speeds but this has been known about for many years so it would be better to ensure it is not simply the radiator.