My GS300 is over heating when driving above 75 MPH but when in a stop like in traffic light it cools down and never overheats so I recently performed the following without any improvement:
1-Cleaned the radiator, added coolant, and replaced the thermostat. 2-Checked both electric fans and replaced the fan clutch. 3-Checked the engine oil for a probable head gasket problem and found it clean and clear.What else can I do? Any idea why overheating occurs when driving fast? And cools down when in a stop?