Cusser
+1y
my uncle said that if there is visible flow in the radiator, it doesn't need to be replaced yet.
Not true at all. Original radiators (1-row) are quite old now, so build-up internally inhibits cooling/shedding of heat. My B2200 had the same issue in 2010, I tried several things (an operational thermostat will NOT inhibit cooling, don't run without one, Mazda or Stant), but the cure was the new radiator, 2-row as the Arizona heat, extra weight of Cab Plus, running AC, uphills on highway (where it was most affected) demands all the cooling I could muster. I still use stock fan clutch/fan set-up (Hayden fan clutch).
2-row all-metal copper/brass Ready-Rad radiator: #433140 from O