Runs hot on highway

[Camper Power]

the truck runs hotter cruising at highway speeds than sitting in traffic, is this normal? the temp guage reads just over 1/4 in town and goes up to just over half on the highway. the rad is a 4 core and was replaced a couple years ago along with the water pump, the coolant was replacced last fall. it does have a fan shroud and clutch.

[69GMCLonghorn]

Typically this indicates a circulation breakdown somewhere. Even though you just replaced the water pump, I would suspect this is your problem.

Also, many people don't think about the engine block itself as being the culprit. 2 things can happen here: 1) It can get plugged up with the same stuff that would plug up a radiator. And 2) if you have a bad head gasket or a slight compression leak due to a crack in a cylinder or head, the exhaust gases can mix with the coolant and cause all kinds of overheating depending on the severity of the leak.

If you have a good radiator shop in town, take it in. They can probably diagnose the problem pretty quickly. Then you can decide if you can fix it yourself or not.

[Camper Power]

sorry if i made it sound confusing but the water pump was replaced the same time the rad was, i cant say exactly when they were replaced cause the po was the one that replaced it, and the engine was rebuilt a few years ago as well. so im not sure if it would be clogged. and im not feeling any signs of compression loss either but im not ruling it out, but id think it would also make it heat up in town aswell.

[WorkinLonghorn]

First thing I'd check,and I'm sure you did already, is the lower hose. Grab it tightly in the middle and see if the metal spring thingy is still intact in there. If not you may be getting a collapsed hose there which of course would restrict flow at higher steady RPM such as cruise.

[Longhorn Man]

i think you are getting wound up over nothing. 1/2 way up on the guage is correct operating temperature.

[Sammy]

I agree half up the stock gage is normal operating temps. Wouldn't get worried till the next mark. Then I would trust a newer gage than an old 40 yr old one.

[Camper Power]

thats why i asked if it was normal in my first post but i guess its kinda hidden too. im just making sure cause im taking the truck for its first major road trip since i bought it, i had a feeling it was normal its just i always hear about people trying to keep their engine from overheating in traffic when im running hotter on the highway.

[67ChevyRedneck]

I have a big ass 4 core in my truck and it takes the old girl a good 10+ minutes (even longer in the winter!) to get up to temp. I'm usually burning down the highway by then. Are you sure it's just not "warmed up" before you're hitting the highway? Does it go back down after a highway trip, or does it stay the same? 1/2 sounds normal to me. If you're worried, install a new gauge with the actual temp on it, that's what I did.

[WorkinLonghorn]

My truck runs at about 1/4 dial all day under all conditions usually. The highest it ever gets is about 1/3 dial on a warm day with a ton or so in the back on the long slow grade up to the dump stuck behind some slow poke.
This is since I got a new 3-row and shroud,but then it hasn't been real hot since then either.
But even with no shroud and a radiator with lots of cross rows sealed shut (to cure leaks),and a totally mashed AC condenser in front,it very seldom hit 1/2 gage.

[88JRFAN]

Might depend upon what size thermostat is in the neck.