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fan clutch question (Again!)

Discussion in '60-Series Wagons' started by Heartworm, Aug 23, 2006.

  1. Heartworm

    Heartworm

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    There have been several threads concerning the fan clutch going on and off while people are driving at highway speeds. My rig (FJ60) certainly does it. There was a previous thread where I asked this question and did not get a response. It would seem to me that there would be no benefit for a radiator fan to come on when you are driving down a highway as you already are pushing a 50-70 mile per hour wind through your radiator. Thus, I am concerned that fan clutches that are doing this on/off thing are defective. Perhaps, there is a thermocouple in the fan clutch that is over-reacting? How does a new fan clutch behave?
     
  2. 2mbb

    2mbb SILVER Star

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    Mine does cycle on and off, more so in summer than in winter. I take comfort in knowing that it is still working. The fan clutch is supposed to engage when the air moving through the radiator reaches a "high" temperature. Since the 2F engine is probably putting out its most heat when at high RPM and high load (highway conditions), I think it's reasonable that the clutch does cycle on. It may not be improving the efficiency of the cooling operation, but the fan clutch doesn't really know any better--it's not like it's controlled by a computer or something...
     
  3. Dynosoar

    Dynosoar Slightly Disturbed SILVER Star

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    Heartworm, You are suffering from a common misconception. Just because the truck is moving 60-70 MPH the air may not be traviling 60-70 MPH through the radiator. Air movement has to do with air pressure. Air will ALWAYS move from an area of high pressure to an area of low pressure. It is threrefore possibe that even at 60-70 MPH little to no air is passing through the radiator. When the fan coupler senses enough heat it will engage the fan and cause a LOW pressure situation under the hood of your truck causing air to flow over the radiator.

    Dynosoar
     
  4. lovetoski

    lovetoski SILVER Star

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    My fan clutch hooks up on the highway when it's hot enough, usually while on a long climb. It runs for awhile, then disconnects...all the while at 40 - 60 MPH. As far as I know, this is normal.
     
  5. Heartworm

    Heartworm

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    I guess its "normal"

    I recognize that many people's cruisers fan clutches behave exactly as mine does..fan clutch coming on and off in hot weather on the highway. I accept the fact that this is "normal" for our 20+ year old rigs, but I still question the engineering of it. Do NASCAR or Indy cars have a fan? Do the radiator fans of other more modern cars with fan clutches or electric fans run intermittently on the highway? Can someone tell me if the fan clutches on FJ60s did this years ago when these rigs were new? When you replace your old fan clutch with a new OEM Toyota fan clutch, does it still do it? My belief is that when the fan clutch reaches a certain temperature, it locks up and starts running. This action cools the FAN CLUTCH off. The reason that it runs intemittently on the highway is that the thermosensor in the fan clutch is over reacting not that the engine is overheating. I wonder what would happen if you took the fan totally off the pulley and ran it down the road...overheat? or nothing? That's my theory, I'm clueless looking for clues.
     
  6. roscoFJ73

    roscoFJ73

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    The spring inside the clutch fan maybe heat sensitve.
    Its a flat coiled spring like a clock mainspring
    Its recommended to replace the spring when you refill the clutch with silica oil.

    Neither of my newish clutch fans on the 3F or the 1HZ locked up above 40 klm