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(Possible) sticky alternator

  • 18-03-2011 07:00PM
    #1
    alanmc
    Registered Users, Registered Users 2 Posts: 1,144 ✭✭✭


    Hi guys and gals,

    I changed one of my aux belts yesterday (because it was squealing slightly on startup when the weather was cold). The change went well. When I had the belt off, I gave each of the pulleys a quick spin to see they were all spinning freely. Started the car up ... no squeal and all pulleys were spinning. Took the car to work this morning. It was pretty chilly when I left and again it started fine with no squeal ... not even a quick chirp.

    When I left work this evening, I was greeted with a sustained squeal and 12V on my voltmeter (not the usual 14V). I had a look under the bonnet and the belt was spinning fine. The PAS pulley was spinning. In fact, all pulley's were spinning except the alternator. I borrowed a large screw-driver from the IT guys and gave it a few gentle taps with the rubber handle and started the car again. This seemed to "fix" it.

    My question is: If I had the belt too tight, could this cause the symptoms above? It's definitely not too loose. The deflection is a few mm less than the belt I took off. Or is it more likely that the alternator is getting a bit sticky? Maybe the bearings going in it?

    I'll take the belt off again tomorrow and have a better look at the alternator pulley. I didn't really look at it that hard yesterday.

    Alan.


Comments

  • #2
    cb900ie
    Closed Accounts Posts: 54 ✭✭cb900ie


    From your description, it is pointing towards an alternator bearing. Was there any whining noise when you spun the alternator pulley with the belt off?


  • #3
    alanmc
    Registered Users, Registered Users 2 Posts: 1,144 ✭✭✭alanmc


    cb900ie wrote: »
    From your description, it is pointing towards an alternator bearing. Was there any whining noise when you spun the alternator pulley with the belt off?

    I honestly couldn't say. I didn't really give it a proper examination. An oversight on my part. I'll take a better look at it tomorrow.

    I think I'll start pricing a replacement alternate anyway.


  • #4
    cb900ie
    Closed Accounts Posts: 54 ✭✭cb900ie


    Pop the belt off again. Spin the pulley fast and listen for noise, then shake it up and down to check for freeplay. Finally, turn the pulley slowly and see if you can feel any tight spots. It has the hallmarks of a bearing problem.


  • #5
    alanmc
    Registered Users, Registered Users 2 Posts: 1,144 ✭✭✭alanmc


    cb900ie wrote: »
    Pop the belt off again. Spin the pulley fast and listen for noise, then shake it up and down to check for freeplay. Finally, turn the pulley slowly and see if you can feel any tight spots. It has the hallmarks of a bearing problem.

    Took the belt off today. The pulley is giving a faint squeak when spinning. It does sound like a bearing problem. There's no give or wobble in it, but I'm sure that's just a matter of time.

    I've ordered an alternator from a vendor on a 350Z forum in the UK. I can't be paying Nissan prices. ;)

    Thanks for your help,
    Al.


  • #6
    cb900ie
    Closed Accounts Posts: 54 ✭✭cb900ie


    No problem. Post back after it is fitted.


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  • #7
    Nissan doctor
    Closed Accounts Posts: 8,223 ✭✭✭Nissan doctor


    It would be unusual for the bearing to go like that in a Z. Was the belt ever changed before? It may have been tightened too much previously.


  • #8
    alanmc
    Registered Users, Registered Users 2 Posts: 1,144 ✭✭✭alanmc


    Nissan doctor wrote: »
    It would be unusual for the bearing to go like that in a Z. Was the belt ever changed before? It may have been tightened too much previously.

    I don't think so. The belt wasn't overly cracked, but it looked like it had been there for a while. It definitely wasn't mad tight when I took of the old one.

    Could my overtightening cause this problem? I might try backing off the idler a little tomorrow.


  • #9
    Nissan doctor
    Closed Accounts Posts: 8,223 ✭✭✭Nissan doctor


    alanmc wrote: »
    I don't think so. The belt wasn't overly cracked, but it looked like it had been there for a while. It definitely wasn't mad tight when I took of the old one.

    Could my overtightening cause this problem? I might try backing off the idler a little tomorrow.


    Nah even if you tightened it too much its unlikely you'd have damaged the bearings in a day or two. Maybe the alternators on the Euro spec Z's come from renault:D


  • #10
    alanmc
    Registered Users, Registered Users 2 Posts: 1,144 ✭✭✭alanmc


    So I came out from work at lunchtime and started the car. Squeal, squeal, squeal. Popped the bonnet and had a good push on the belt. It seemed bloody loose.

    So when I got home, I nipped the tensioner up a few more turns and started the car. No squeal. I'm ashamed to say it (after my insistence that it "definitely wasn't loose"), but I don't think I tightened the belt up enough.

    Also, I think the belt stretched a little as it bedded in.

    I'm going to put my alternator order on hold for a few days and see what happens.


  • #11
    PADRAIC.M
    Registered Users, Registered Users 2 Posts: 2,189 ✭✭✭PADRAIC.M


    Belts don't really stretch a whole lot you really want only about an inch travel in the tension of the belt


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  • #12
    alanmc
    Registered Users, Registered Users 2 Posts: 1,144 ✭✭✭alanmc


    PADRAIC.M wrote: »
    Belts don't really stretch a whole lot you really want only about an inch travel in the tension of the belt

    You may be right about the belts not stretching. I probably didn't tighten it correctly.

    But an inch sounds like way too much travel. The service manual of my car says 3.5-4.5mm for a new belt under 10Kg load. Roughly translated - pretty effing tight.


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