Overheating on the highway- 98 2.2

[darmstro]

I have a 1998 Sunfire with the 2.2 motor. The car is ok in the city, but after about 20 minutes on the highway it starts to heat up. It will run into the top 1/4 of the temp guage but not much further, hasn't run into the yellow or past the white line.

When I get off the highway I can let it idle and the temp will go back down and stay right in the middle. T-stat is opening and the fan's kicking on, I'm thinking it may be the water pump.

Anyone else have this problem? I've only ever had vehicles that will heat up during city driving or while at idle and it's usually a fan or t-stat problem, never had one that heats up on the highway.

Should also mention that the heat blows hot and the AC blows ice cold.

 

[melsg5]

Water pumps usually fail and leak at the bearing. I would try replacing the thermostat and flush the radiator with a mild cleaner found at an auto parts store. At highway speeds the air rushing through the radiator performs the heat transfer function and in the city and at idle the fans kick in to add airflow through the radiator.

 

[darmstro]

I ordered a new waterpump and have the t-stat and temp switch. I think I'll just replace them all while I'm working on it. The parts are fairly cheap so it's not a big deal. I hate fixing something only to have to go back and fix something else.

Thanks for the reply.

PS. What's the capacity of the cooling system?

 

[melsg5]

a little under 3 gallons when completely empty