Whistle/high pitch squeal from front of engine

Discussion in 'Trucks [ Eighteen Wheelers ]' started by Dorsey, Mar 14, 2014.

  1. Dorsey

    Dorsey Medium Load Member

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    I have a c15 mbn engine. About a month or so ago I heard a high pitch squeal/whistle from the front of the engine. After that day it went away. About a week ago it did it for a little bit and went away again. Yesterday the noise came back. I havent drove at all today yet (trying to replace an airbag) so I dont know if the noise is still there. When it does do it driving down the road you can hear it when your coasting I've noticed and when you get on the throttle it goes away. Ive tried to pin point the noise at the front of the motor but I can't tell where its coming from.
     
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  3. Lowa3468

    Lowa3468 Heavy Load Member

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    Could be either tensioner or the belts to alternator to rule out belts spray water on belts when running if noise stops then I would say its belts, if squeal still there by what you described I would say tensioner pully
     
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  4. dude6710

    dude6710 Road Train Member

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    I had to replace two idler pulleys and my tensioner last week. All were bad bearings and made noise when I was sitting. Going down the road it cooled them down enough not to.
     
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  5. JPenn

    JPenn Road Train Member

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    Bearings in those are cheap and very easily replaced if you have access to a shop press. There's a good video on YouTube with a how to and bearing part numbers.

    http://m.youtube.com/watch?v=zWaIrwW6qqY
     
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  6. Lone Ranger 13

    Lone Ranger 13 Road Train Member

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    When my pete was new I started hearing a squeak like a bad bearing coming from the front of the engine. The cause: the radiator was a little loose and it was making the squeaking noise. The mechanic tightened the mounts and it never made the sound again.
     
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  7. Joetro

    Joetro Road Train Member

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    My C-13 did that awhile back. It was the idler pulley. 45 minutes and a $200 part later, I was on my way.
     
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  8. rollin coal

    rollin coal Road Train Member

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    Probably needs belts tightened up or new ones. My mbn does not have a tensioner pulley.

    Edited, well it does have a tensioner on the lower belts but up top is tensioned by adjusting the alternator. Looks like the tensioner would be easy to pull off and probably very cheap to just press in new bearings as suggested by another member.
     
    Last edited: Mar 15, 2014
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  9. Dorsey

    Dorsey Medium Load Member

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    Thanks. I didnt hear the noise again the other day. The last 2 times I heard it I did have a winter front on. So I guess that helps the bad bearings get worse.

    I should be able to put a temp gauge on it and pin point the problem. Correct?
     
  10. JPenn

    JPenn Road Train Member

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    If you can hear the bearing squeal above the sound of the motor running, it's only going to be a short while before it seizes. Slack the belt and turn the pulley by hand...if there is any crunching or it's difficult to turn, replace the bearings. Another giveaway I've noticed is while the motor is running, the spring loaded tensioner pulses, as if the pulley is occasionally resisting, then freeing itself. It's especially apparent when you see how smoothly a pulley with brand new bearings spins.

    Of course, your noise may not be the tensioner at all. But if it is, now you know how to deal with it :)
     
  11. Joetro

    Joetro Road Train Member

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    Easy, yes. Cheap? No. Part cost $200 and wasn't even painted yellow.
     
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