My 4wd SR5 is overheating – in winter, heat is slow to warm up; in summer, after 30 minutes, car overheats. Radiator fan doesn’t sound like it changes speed – how does the fan clutch in this vehicle work? Could that be the problem? No coolant leaks or noises.
The problem might be caused from a stuck thermostat.
If the thermostat is stuck partially open, it will take longer for the engine to come up to temperature so it takes longer before there’s heat. If the stuck thermostat fails to open completely, the coolant isn’t able to leave the engine fast enough so the engine overheats.
So check for a stuck thermostat before anything else.