Hello, I have a 2004 Dodge Neon SXT, around 153k miles, that i'm having issues with. It is overheating when I'm driving for long distances on the highway, but fine around town. I drive back and forth between my parents house and my house, which is 6 hours away. What is happening I can drive for about 3-4 hours going roughly 70 mph and it then the temperature will just slowly start to rise. I can turn on the heat full blast and it will drop my temp but pretty much as soon as I turn my heat off it will start to climb again. The fans are working correctly and I changed the thermostat this past winter, roughly 8 months ago. I just had my coolent flushed thinking it would take care of the problem since the coolent was just nasty rusty looking. The fluid is now clean with a little bit of brown specks in it. So I'm just wondering if it would be radiator just so corroded? Do I need to replace this, or could it be something else, like a blown head gasket. I haven't noticed any coolent in my oil and vice versa and haven't noticed coolent loss, besides what boils out of the resevor when it overheats and I stop. I'm at the end of my rope on this car and about to just trade it in even tho I love it, lol.

 

- Open the radiator cap (Do not open it when the engine is hot, or you will get burn).
- Start your engine, and let it idle.
- Turn the heater on.

If the system has air in it, this will let air out.

 

Also noticed that when the engine gets hot, the transmisson acts funny when shifitng, like it almost slips when the engine is hot

 

If this doesn't fix it. You may need to replace the radiator cap.

 

On our old toyota, it will not shift to 4th gear when the engine is still cold.

You just need to fix the heating issue, and your transmission will shift smooth again.

 

I hope it fixes it, would be so much better if it was that easy of a fix lol

 

Your cooling system is not transferring heat efficiency.
You can run a little lean I think, but the temperature shouldn't rise up continually like that. The engine would ping before that happen.
If other mechanical failures like blow head gasket, the engine wouldn't start up right away, and run smooth like that.

 

if your trans is shifting funny, after you get the cooling issue corrected see when the last trans fluid change was done, its easy and cheap to do as well.