Peterbilt 379 Fan clutch Squeak when engaging.

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Don379, Apr 29, 2021.

  1. Don379

    Don379 Medium Load Member

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    Peterbilt 379. Fan clutch was replaced 3 years ago. ITs always had this loud annoying screech when it engages. Would like to finally figure it out. Few notes: ITs not the fan belt or the tensioner. I replaced all that thinking it was the issue. The noise is indeed coming from the clutch when it engages.
     
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  3. Goodysnap

    Goodysnap Road Train Member

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    Sorry Don,

    Revisit your belts. Tis not the clutch.

    Are you sure you dont have any worn pulleys? Are we talking v or serp? If v and manual adjust, how did you set the tension?
     
  4. Smellfunny

    Smellfunny Road Train Member

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    You might could try a new solenoid that supplies the air to it. It may not be putting air to the clutch fast enough. Might not make a difference but it is where I would start. Basically you have a clutch engaging and it is making that noise because it is probably grabbing it when the fan is stationary and the hub is spinning at who knows how many RPMS. I would squeal too. : )
     
  5. Don379

    Don379 Medium Load Member

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    Thanks goody snap. SERP belt. I think 6 groove. I tried new belt and new tensioner from cat to try and remedy. Same dang problem. Cats tensioner is self adjusting and i have to back it all the way out with socket wrench to barely slip the belt under it. Can’t tighten it anymore. I have a buddy with same set up and his is nice and quiet engagement. I’m jealous.
     
  6. Don379

    Don379 Medium Load Member

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    New solenoid also my friend
     
  7. God prefers Diesels

    God prefers Diesels Road Train Member

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    Long shot, but have you looked at your crank pulley grooves? They get rubber in them, and cause your belt to ride high. Then it squeals like a pig. I pulled my belt off and ran the engine while I held a flathead screwdriver in each groove. #### going everywhere. Finished with a wire brush. No more squeak.

    Learned the trick right here on TTR.
     
  8. AModelCat

    AModelCat Road Train Member

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    I also suggest checking the pulley grooves on the hub and crank pulley. Belt should ride on the sides of the grooves, not the points. If the grooves have worn down, the belt will sit low and won't grip the pulley properly.
     
  9. Smellfunny

    Smellfunny Road Train Member

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    Clean the grooves and look for wear on them. You aren't supposed to use belt conditioner on serpentine belts but if you did that would let you know if the belt is the culprit for sure.
     
    Rideandrepair, Don379 and lester Thank this.
  10. Don379

    Don379 Medium Load Member

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    Thanks everyone!
    I will be pulling belt off and cleaning pullies this weekend
     
  11. Don379

    Don379 Medium Load Member

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    Well friends, the fan pulley was indeed nasty and had to use screw driver to get the old gunk out and then wire wheel. (see picture below). Unfortunatley, it is still making that nasty squeek when i cycle the fan switch. I also included a pic of how the belt is routed. Im coming to the conclusion it needs to wrap around the clutch pulley better than it is. I can pull the fan by hand toward me where i took the picture and it will turn the crankshaft over, if i push the fan away from me, it just slips on the belt and not spin the motor over. That tells me it needs to wrap around the fan clutch at a downward angle instead of straight across to the alternator. It is a cat c12 2ks. My shop manual and parts cd does not show routing. Maybe there is a pulley in the parts manual that will mount on a downward angle to wrap at downward angle and purchase longer belt. What is you guys thoughts.

    IMG_4579.jpg IMG_4582.jpg
     
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