Hello, today when i was on my way to work i drove about 50 miles on the highway, about 4 miles from my exit i noticed my temp gauge getting higher that normal. today was the hottest it has been all year about 90F. when i got off at my exit the temp started to decline back to normal. the next 5 miles was back roads and when i arrived i let the van run at idle for about 15 mins. the temp remained normal.

Van specs are 97 2500 3.9L 150,000 miles a/c auto.

over the winter i flushed out the heater core due to no heat, it was clogged. i replaced the coolant and replaced the t-stat. all winter/spring i have had no cooling problems until now. due to the sediment in the heater core my friend recommended changing the water pump, he also said i should be getting more heat than i was. every time the engine was revved up the air got hotter out of the vents. I'm not sure if this has anything to do with it but i figured i would post my observations. could it be the water pump is not pushing enough fluid at high rpm's?
thanks in advance

 

Your water pump is fine but your radiator is plugged up...time for a new one.