My fiance's neon is over heating on the highway. It is fine around town but the temps slowly rise going down the interstate (Had to use heater to keep temps out of the red). Both fans seem to operate fine, thermostat seems to be working, and I replace the radiator cap.

I plan to flush the coolant tomorrow or I my replace the radiator. I could keep the temps out of the red by turning the heat on. Any help would be greatly appreciated.

2004 Neon SXT
79,000 Miles

 

Sounds like a possible blown head gasket or a bad water pump. Are the radiator hoses firm or soft?

 

What is the condition of the radiator cap (does it hold the correct PSI still) and it's gasket?

 

I replaced the cap just to rule that out. I replaced the radiator last week and it seemed to cure the overheating, but tonight she told me it started to overheat again. I guess I'll replace the thermostat today and see if that helps. I think it had the original coolant in the system before I flushed it (looked nasty).