I finally got my 1986 FJ60 (2F) running. I have noticed a strange engine noise when cruising on the interstate (running about 2500 rpm). It sounds as if the engine speed is increasing (it hums or "whines" louder intermittantly). It will make this sound off and on about every 2 minutes and it lasts 20 o 30 seconds. None of the gauges move (oil pressure, volt meter, tach, heat gauge) and there is no change in speed or engine performance. If I let off on the gas and coast with the clutch disengaged, the sound immedialtely is gone. Could it be the radiator fan running off and on? Or the air flow into the air cleaner being switched from the outside to the manifold?