99 Neon Overheating on hwy

[joynbec]

Hey,

I have a 99 Dodge Neon Sport addition. It has well over 155.000 miles on it. And recently when going down the highway at like 65-75 the car over heats only if the Air condition is on on extremely hot days like 90's... It starts to overheat within 10 min of driving down the hwy. I have had the radiator flushed, and replaced 2 radiator hoses, also they blew out the radiator with high powered air... We could be driving arround town for hrs and it not over heat. It is only when driving down the highway on hot days with the air on. it can even be on low. If we do have the air on it still blows cold air when it starts to over heat. If we do not turn on the air going down the hwy.. it is perfectly fine... Do you have any idea's?

[das2123]

Check thermostat, temp sensor, and with that many miles don't rule out a bad radiator.

[gotvtec4u]

Replace the radiator. they may look ok and hold coolant but the radiator breaks down over time and cause improper coolant flow at mid to high rpm ranges. since the neons, depending on a/t or m/t run at 3-4 thousand rpm at 60-65.

[m78jo]

mine used to do that also. and i had to replace the radiator cap and ever since its been fine. your seal might not be tight even though it looks like a new cap.

[Bear]

Are the aux fan/s working? if unsure, start car and turn on AC and then look at the fans.