Page created by T Feb 25th 2009:
The Fan Clutch contains a mini Torque Converter. The Torque Converter is like 2 little Fans connected by very thick Silicon based Oil . A Thermosensitive Spring in the front of the Clutch rotates with Temperature and causes a Valve to force the Oil along a long or short Path dependent on the Position of the Front Spring. The Position of the Front Spring is determined by the Air Temperature. When the Temperature is hot, the Spring rotates the Valve so that the Silicon Oil has to travel the longer Path. This gives the Fan a maximum speed of 2300 RPM because the coupling is firmer. When the Temperature is cold, the Spring rotates the Valve so that the Silicon Oil has to travel the short Path. This gives the Fan a maximum speed of 1100 RPM because the coupling is lghter.
A good Fan Clutch will have very little wobble (play). When you spin it cold it will freewheel briefly then stop. It will not be leaking Oil.
Cover the Front of the Radiator with a Sheet of Cardboard to limit the Air Flow. When the Temperature Gauge shows high Temperature, increase the Engine RPM and watch the Fan. It will activate at the higher RPM until the Engine cools down again.
The Fan freewheels and never engages properly. Replace the Clutch. ====Loss of Power:====The Fan is jammed solid never allowing the the Fan to slow down at higher RPM. Replace the Clutch.
The Clutch is leaking Oil. Insufficient oil will cause a loss of RPM which will mean too little air moved. Replace the Clutch. ====Noisey:====The Bearings are worn out in the Clutch. Replace the Clutch. ====Excessive Play:====The Bearings are worn out in the Clutch. Replace the Clutch.
Fan Blade Stagger:
A patent exists, relative to gas turbine engines, that claims Fan Blade Stagger reduces blade twist. Reducing blade twist minimises the vibration that would be caused by the blades being twisted out of shape. Part of the theory is also that the leading edge of some blades be masked by the trailing edge of another to minimise the aerodynamic result of the leading edge blade impacting turbulent air.