It's been a while since ive been on here but i got a whole new bucket of problems with a new project ive taken on.
1997 eclipse gs almost stock 120,000 miles

the problem is the car is overheating while driving on the highway only. around town or idle its fine but as soon as you get on highway and drive 65mph or faster it slowly climbs to 3/4 and eventually all the way up to hot on temp gauge. One problem i know it has is the heat blows cold.

what ive done so far:
changed thermostat twice
changed coolent temp sensor
replaced rad cap
flushed coolent system
Changed waterpump, timing belt, tensioner

car still does the same thing. Fans kick on both rad hoses get hot.
no CEL
compression check read 175,195,195,195
no coolent in oil
no oil in coolent
Any ideas? thanks in advance

My car is at the same mileage.

I wish i knew what the hell was going on with mine.

First it overheats and blows a heater hose on the t-stat, then it overheats idling, now it runs fine.

My gas mileage is in the shitter. Half a tank got me 118 miles.

I wish i could help you. I did a search and alot of these coolant issues end up unsolved mysteries. What gives?

Yeah i feel your pain i believe i have it narrowed down to either a leaking headgasket (with no signs to prove this besides overheating) or a bad engine computer. Unless someone on here knows otherwise ive just never known a car to not over heat at idle but over heat while driving on the highway. Reguardless i know i will fix it hopefully with some help here.

these cars do have their issues however when running good they make one hell of a car. My 98rs had one problem after another and in time and years on this site i was able to fix everyone of them. Im in the process of a compleete rebuild on another 420a we just picked up so the problem will be fixed i just want to find out the source before i swap this one out.

Bypassed the heater core and car still overheats so that eliminates the possibility of the heater core being blocked up or something. still cant figure out why heat blows cold? anybody?

make sure you don't have a bunch of crap clogging air from the ac condenser to the radiator.

I had a similar issue with my Eclipse. Are you absolutely certain that there is no air trapped in your cooling system? If not try "burping" it.

Yeah did the whole burp thing still same issue.