Is it the decoupler or the alternator bearings?



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Thread: Is it the decoupler or the alternator bearings?

  1. #1
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    Is it the decoupler or the alternator bearings?

    In the last week or so of driving, I've noticed a low, rhythmic, ruh...ruh...ruh.. noise coming from the drivebelt side of the engine when the engine is under load - A/C compressor, putting it in gear, running quite a few accessories, etc.

    I've scoped the source of the noise (long screwdriver to the head-style) down to the alternator assembly, but I'm wondering if there's a test that can be done that will tell me whether I should just replace the decoupler pulley OR whether the bearings in the alternator itself are on the way out, and I just need to swap the whole thing.

    Any ideas?

    Nate
    '05 Town & Country Touring
    3.8L 167,000 mi

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  3. #2
    T&CFan Guest


    Two of the three Chrysler minivans we owned before our current one had to have new alternators at about the same mileage as yours (the fourth didn't make it that far due to accident). I imagine someone here can answer your direct question about which component to fix, but I'm wondering if sometime soon yet another will fail on it and you will probably end up replacing the entire assembly anyway. Just my two cents worth (and even at that the advice is overpriced!), but maybe it would be worthwhile to replace the alternator now and be done with it. -Ken

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    1 out of 1 members found this post helpful.
    I'd say it's the decoupler making that sound. My 03 has been making that sound for a while now. I took the cap off of the decoupler and sprayed a little PB blaster in there, it helped for a little bit, but not long. I'm just going to wait until it completely breaks or the alternator quits charging.
    Jeff
    http://www.facebook.com/eddie.munster
    Current:
    2007 Grand Caravan/3.8L V6/103K mi/original 41TE
    2006 300C/5.7L HEMI V8/128/K mi/original W5A580
    2002 PT Cruiser/2.4L I4/139K mi/original 40TE
    1992 S-10/4.3L V6/249K mi/original 4L60E
    Previous minivans:
    1997 Grand Voyager SE/traded@192K mi/3.3L V6/original 41TE
    2003 Grand Caravan Sport/3.8L V6/traded@124K mi/original 41TE
    2007 T&C/3.8L V6/traded@44K mi/ original 41TE
    2010 T&C Touring/3.8L V6/the ex's@72K mi/original 62TE

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    My 03 T&C was the alternator, sounded just like you describe. It quieted down nicely once the alternator was replaced. I originally thought it was A/C but tech used his trusted noise finding device (a long metal pole) to listen to it directly and got it right.

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    My alternator started to make a whirring noise at about 160,000 kms (100,000 miles). Replaced it and still have the old decoupler on there.
    If an alternator bearing is bad, I would expect a whirring sound. Put your hand on the alternator and see if you can feel roughness or vibration. If working properly, it should be running smoothly.
    A Mechanic's stethoscope may help "pin point" the noise.
    The noise you describe sounds pulley related. Any particular noise at shut down or startup? Thats when the decoupler comes into play.
    2007 GC SXT - Magnesium - S&G - 3.8L - 115,600 kms
    2002 GC Sport - Stone White - 3.3L - 314,240 kms
    2003 Jeep TJ Sport - 4.0L - 246,430 kms

  9. #6
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    Quote Originally Posted by Jeepman View Post
    My alternator started to make a whirring noise at about 160,000 kms (100,000 miles). Replaced it and still have the old decoupler on there.
    If an alternator bearing is bad, I would expect a whirring sound. Put your hand on the alternator and see if you can feel roughness or vibration. If working properly, it should be running smoothly.
    A Mechanic's stethoscope may help "pin point" the noise.
    The noise you describe sounds pulley related. Any particular noise at shut down or startup? Thats when the decoupler comes into play.
    There's no particularly strange noise at shut down or startup. I would compare the noise as a diesel-like rumble, very rhythmic, coming from the alternator, only when the engine is under load. I may go take another listen to startup/shutdown noises later today and update if I hear anything different.

    Nate
    '05 Town & Country Touring
    3.8L 167,000 mi

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    Mine has the diesel like noise as well but only at idle, plus the whirrr spin down when I shut it off. (I might be due for both alternator and pulley) Does your noise go away as soon as you increase RPM? Do your lights flicker or do you notice a dim of lights and fan when coming to a stop?
    2002 Town & Country Limited 150K
    2007 Toyota Avalon
    2002 Honda Accord

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    It is the pulley. Autozone or advance auto parts do not sell the pulley just the alternator. Napa sells the pulley for $80 plus have to find or purchase special tool to remove and install. I ended up buying at advance auto parts for I think around $160 with a lifetime warranty. Once alternator was replaced, noise went away and wife was very happy and not embarrassed to drive kids to school anymore. lol

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    Quote Originally Posted by PTXer View Post
    Mine has the diesel like noise as well but only at idle, plus the whirrr spin down when I shut it off. (I might be due for both alternator and pulley) Does your noise go away as soon as you increase RPM? Do your lights flicker or do you notice a dim of lights and fan when coming to a stop?
    The noise goes away as I increase RPM, and I do not notice any dimming of lights or fan when I slow down RPM.

    At this point, I've got one of the Miller tools on its way to me and I'm planning to swap out the pulley some time in the next couple weeks (God willing it doesn't fail catastrophically before then). I've got a vice that I need to mount to some lumber as well before I do the job. Haynes says to remove the alternator by way of moving/removing the oil dipstick tube, but I've read in a few threads on here that going via removal of the EGR valve is easier. It looks to me like the space I'd open up by removing the EGR valve would be larger - is that the way to go, Haynes be darned?

    Nate
    '05 Town & Country Touring
    3.8L 167,000 mi

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    Nate,

    I had the pulley noise about a month ago (I replaced my alternator given my location, the apparent lack of a pulley tool locally, and the cost of said tool).

    Possibly out of complete ignorance, I removed the alternator without removing the dipstick or EGR valve. The "lower front" bolt was a bit tricky to remove, however, patience and a open ended wrench served me quite well.

    Honestly, it was one of the easiest DIY jobs I've had to do - I hope you have the same luck!

    Cheers,
    radman
    2003 DGC Sport, AWD, 3.8L: 135,000 km
    2006 Subaru Forester, 2.5L: 130,000 km
    1974 VW Type I: 0 miles on "rebuilt", ahem, unassembled engine someday, my pretty, some day ...

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