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Old 02-26-2001, 06:39 PM
Jerry Turben Jerry Turben is offline
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Can someone bring me up to speed on viscous (clutch) fans? I have taken them on and off before but never really understood how they work, when they are broke, or when they are half broke. Do they totally lock up hot? Are they to spin free cold? How does one bench test a unit? Did Chrysler use more than one style? Is one style better than other? My local auto parts store listed several up to 85,(6 & V8) then one 86 and up. Mopar performance lists one but I have two or three already that may be good, but they all act different. Any info, or hard learned lessons will help. Jerry Turben
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Old 02-26-2001, 07:47 PM
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The-Challenger The-Challenger is offline
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hi jerry I have had two clutch fans go bad. one seized up the other quit spinning enough to cool the engine.
there are two different kinds one kind had a thermal spring to help cooling when it gets hot these usually are on trucks with tow packages. the other just has the vicious fluid in it and they work fine on cars and trucks.
if you use an old one check to make sure it does not have a stain from leaking fluid near the bearing seal.
i think you can get a standard one at the auto parts for about 25.00. I hope this helps.
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Old 02-27-2001, 01:41 AM
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Hammer 74 Hammer 74 is offline
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I think Chrysler had a few different size pilot holes that mate with the water pump. Maybe a BB and SB. If there is fluid leaking out it is bad. You can tell because the amount of air passing around it deposits dirt on any oil leaking out. When the car is cold you should not be able to spin the fan very far. If it freewheels it is bad. Good may be 1/8 turn.
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Old 02-27-2001, 12:41 PM
ChristianCuda ChristianCuda is offline
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The big blocks and small blocks have the same mounting holes but some need to be longer or shorter depending on a/c cars or small block/big block

Christian
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Old 02-28-2001, 05:38 PM
reygus reygus is offline
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The Thermal Control Drive is essentially a silicone fluid filled coupling betweent the fan and the fan pulley. The unit allows the fan to spin in a normal manner at low engine speeds while limiting the fan top speed to a predetermined amount at higher engine speeds. The thermostatic spring on the front face of the unit senses tempreture from the radiator air and engages the drive unit for more fan speed if the air tempreture coming through the radiator rises above a certain point.
The fluid fan drive should be replaced if there is indication of a fluid leak, if noise or roughness is detected when turning the fan by hand, if the unit cannot be turned by hand, or if the leading edge of the fan can be moved more than 1/4" front to rear, meaning the fan can be wobbled back and forth.
This came, verbatim, from the 1977 C-P-D service manual. Hope this helps.
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