My in-laws have a 97-ish Dodge Stratus. It overheats after cruising on the highway for about 3 hours. The thermostat has been replaced and the car does not overheat in city driving, but then again, it does not run for 3 hours at a time in the city. Both cooling fans are operational. What would cause a slow to overheat problem? I would think that the only thing left would be that the water pump is going bad? Any other suggestions?

 

Hmm, so it only heats up on the highway?

Check the lower radiator hose to make sure it's not collapsing? Also, not sure if those cars come with airdams but if they do, make sure it's still attached.

 

Let me take a wild guess...

It has over 70,000 miles. You open the hood and it says "Mitsubishi" everywhere. It has aluminum heads. It's never had the cooling system flushed.

Ask the in-laws if they still have the owner's manual for the car. Search the Maintenance section for the schedule of planned maintenance, then see just how far off the mileage/age is from most of the required maintenance. Still a mystery?

 

LOL, man I never would have thought about that.
Like the time my GF was like my Blazer needs a tranny fluid change, I'm like well when was the last time (she got it from her parents with like 185k miles no, already have a rebuild once.) She's like I don't know, and neither did her parents.. It's like well gee that's good too know, 185k miles and don't know if the fluid has been changed since a rebuild.

 

Good point. It is a used car that they bought a couple months ago. I don't know the milage, but good suggestion.

 

It certainly sounds like a poor heat transfer issue, and that is usually due to scale and corrosion, or possibly radiator tube blockage (usually for the same reasons).