Drive it , when it gets hot stop and feel the radiator. If you feel any cold spots it's clogged. Does it overheat while idling? If it doesn't I'd suspect the radiator. My V8 dakota was getting pretty warm while driving in 90 degree heat but would idle all day with no problems. Felt the radiator, half way down was cold. I drained the coolant, put 1 gallon of Purple Power in the radiator, topped off with water, ran it for 30 minutes, drained, flushed, refilled with antifreeze, problem gone, now the radiator is hot all over, cold spot gone. I never tried it before but didn't want to spend the 205.00 for a new radiator so I tried it and it worked good.