My 1994 toyota 4 runner overheat while driving on the highway but not in town. on 1994 Toyota 4Runner

On the highway it gets hot when rpms are low but driving in town shifting the gears it cools to normal temps its a manual transmission, no water in wonderin if theres a sensor or anything else that would cause this.any help would be great.
Thank you.

Asked by for the 1994 Toyota 4Runner
ck coolant level to start with, then pressure test cooling sysytem for leaks if low.if not low seek a diag for cause
Level is good, new radiator in it guess i will pressure test.
1 more answer , 2 more comments
Does it stay cool on highway with RPM's high, or is this normal highway speed RPM's. Possible Radiator
Normal highway speed when rpms are high it stays cool when low rpms get hotter
Cooling fan, weak water pump, low flow at low rpm.