91 5.0 Lx Runs Hot On Freeway, Cool In Traffic

[blackLX91]

Ok my car is pretty much all stock. Its a 91 with about 30k miles original on it. I have a few bolt ons and exhaust on it but no engine mods. I took it on a longer trip a few weeks ago and i noticed at about 45 miles away from home that the temp gauge is reading towards the warm side. I pulled over and checked the coolant and all ok. Drove the rest of the trip while keeping a close watch on the situation. Once home i changed the thermostat to a 180 and flushed the system. Also replaced the fan clutch. Now still having the same problem. Runs warm on the freeway, normal to low at lower speeds and in traffic. WTF?? Anyone seen anything similar?

 

[Noobz347]

I've seen that happen before with folks who have installed ram air hoods and/or installed deleted items that messed with the air flow on the nose.

You have anything like that?

 

[blackLX91]

No. I even have the stock air dam in place. I can't figure it out.

 

[ratio411]

Lower radiator hose sucking shut at sustained rpms.

 

[Dino Dino Bambino]

Runs warm on the freeway, normal to low at lower speeds and in traffic. WTF?? Anyone seen anything similar?

Yes, those are typical symptoms of a clogged radiator core and the cure is a new radiator.

 

[2000xp8]

It's probably the radiator, get yourself a nice 3 row and you should be good.
Antifreeze becomes acidic when it sits, so even though it has low miles, the radiator gets destroyed from the inside out.