i know,another overheating thread, sorry.I searched and couldn't really find what i was looking for. My car runs fine in the city with the ac on, temp reads below the half mark. On the highway though i have to drive with the heat set to hot and the fan off, as soon as i set it to cold (not ac just to cold) it starts climbing slowly and stops at about the 3/4 heat mark.If i turn the ac on forget about it, it climbs from half to full in seconds.a lot of times when i park my car the coolant bubbles in the res for a few minutes then stops. It was doing this at the end of lastsummer too so i changed my rad cap and flushed and refilled my coolant with no change at all. in the manual it says that if the upper rad hose is hot then it won't be the t-stat stuck closed so i haven't changed that yet. anyways let me know what it could be. oh and my fans come on when they should, not like it matters on the highways anyway. thank you

 

sounds like its time for a new radiator.
its common with neons for the radiator to get clogged easy or for the fins to rot and start falling apart.

 

yeah that's what i think too. i modified my thermostat so it's always open and that never remedied the problem so i guess it's time for a new rad. how much does a new rad cost aproximately? thanks for your help

 

actually to be honest if you cut the thermostat open, that will cause it to overheat with extended higher RPM because the water flows too fast and isnt in the radiator long enough to get the heat out of it...
ive bought a couple $75-$80 ebay radiatos and had good luck with them in my race cars. i use them because thats usually the first thing to get smashed.
try a new stat first then if that dont work probly go for a radiator.
you could even try hosing it out backwards, they can get alot of dirt and bugs packed in there and leaves between the AC condensor and radiator.

 

hmm interesting, i never thought about it like that. i do have a new thermostat sitting on my passenger seat so i will throw that in first thing in the morning and see.

 

Make sure you put the Anti freeze in the thermostat housing instead of the container in the rear of engine bay, I've noticed this has helped my car not overheat, some reason it doesnt suck good enough to inject that antifreeze so it overheats. I have to cap offmy antifreeze every month...lol