Fitment: 1996-2002 Toyota 4Runner 1995-1998 Toyota T100 1995-2004 Toyota Tacoma 2000-2004 Toyota Tundra What is a fan clutch? A fan clutch is a thermostatic engine cooling fan that can freewheel at low temperatures when cooling is not needed, allowing the engine to warm up faster, relieving unnecessary load on the engine. As temperatures increase, the clutch engages so that the fan is driven by engine power and moves air to cool the engine. .