Pete 379 1996 engine fan

Discussion in 'Peterbilt Forum' started by rulonj, Aug 18, 2019.

  1. rulonj

    rulonj Bobtail Member

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    Aug 18, 2019
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    The fan won't engage until the clutch itself heats up via the heat coming off radiator or engine, and only with the engine fan switched to manual. The truck is missing the fan shroud. May be more than one problem here. Thinking of starting with a new shroud. Any suggestions?
     
    cke Thanks this.
  2. Dino soar

    Dino soar Road Train Member

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    You're thinking of the way clutch fans work on automobiles and light pickup trucks.

    I don't think any big truck engines work like that. The big trucks use air to turn the fan on or off. There is a thermal switch that senses the temperature of the engine and that activates a solenoid that will turn your fan on.

    The fan is not supposed to turn when the engine starts, only when you reach a certain temperature. The manual switch that you have inside the cab should turn the fan on manually if you flip it.

    You definitely should have the right fan shroud because that will help to keep you cool when the fan does come on.
     
  3. rulonj

    rulonj Bobtail Member

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    I know it sounds strange, but that is what's happening. Air system pressure is up engine fan is switched to manual, you can hear air leaking within the clutch, but it will not turn on till I drive a while. And it won't turn on at all when switched to auto (it will overheat in auto). I know what your saying about light auto fan clutches. Doesn't make any sense. It will switch on and off after everything is warmed up though. Just wondering if I should get a new fan clutch or if there's something else going on.
     
  4. Dino soar

    Dino soar Road Train Member

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    If you hear air leaking within the fan clutch then make sure it's not coming from the fitting, but other than that it will have to be rebuilt. You should not hear any air leaking from there whatsoever. Start there and see what that does for your problem.

    If you wanted to check it, you could put your own air supply to the fan clutch and see if it locks up. But if you hear air leaking and you're certain that it's leaking from the fan clutch then it's time for a rebuild.
     
  5. rulonj

    rulonj Bobtail Member

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    Ok thanks a million. I'll try that
     
  6. thejudges69

    thejudges69 Light Load Member

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    If you have air leaking, then the clutch is not fully engaging and is slipping, that's causing the fan to create heat.

    You need a shroud first of all, you need to channel the heat from the radiator to the fan, that can make a huge difference on engine cooling performance.

    The alarmastat for the fan controls it's operation. They all have different temp settings. For example, my alarmastat is set at 205 degress for the fan to come on. They have higher and lower set switches. How hot have you let it get to see if the fan will engage? There are some alarmastats that won't power the fan until 220 degrees.

    Get a shroud, get your equipment right, that's first and foremost. Pride in your ride. Find the air leak, if it's a fitting, fix it, if it's internal to the clutch then you'll need to replace or rebuild. If you have to rebuild that's easy. If your mechanically inclined it's a few hour job. Kitmasters makes the best rebuild kits, Horton is ok, but kitmasters has a better bearing assembly..
     
  7. rulonj

    rulonj Bobtail Member

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    Aug 18, 2019
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    Done deal new shroud installed and reman fan clutch. All better! Thank you!
     
    Dino soar Thanks this.
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