Overheating only highway speeds

[82ndparatrooper]

Hey fellas my 88 burb in only overheating on highway speeds. Running at normal temps when driving in and around town. I have your normal 350 EFI. Any ideas fellas? Thanks much

 

[DoubleDingo]

When was the coolant replaced? Is the radiator plugged inside? Is the radiator fins plugged or blocked?

 

[SkinnyG]

When was the coolant replaced? Is the radiator plugged inside? Is the radiator fins plugged or blocked?

+lots. This.

 

[82ndparatrooper]

Actually it's been a while... I'll flush it and get back you guys with an update

 

[smoothandlow84]

Do you have the spring in the lower radiator hose? If the spring isnt in the hose, at highway speeds, the hose collapses and will cause overheating. Also flush the coolant and install a new thermostat and gasket. Possibly replace your radiator hose also.

 

[circuitguy]

Might have a plugged cat converter.

 

[89Suburban]

Could also be a bunch of leaves and junk plugged up in front of the bottom 4" of the radiator where you can't see.

 

[87scotty]

All stock?

 

[82ndparatrooper]

Hey guys I flushed radiator and changed the stat, that did the trick. I really appreciate the help fellas.