Issues with keeping the Alternator In?

[cglomstad]

Have a 77z and about every two weeks (I believe) a bolt starts to vibrate out then snap off underneath the alternator in one of the two arms. Its happened four times now. The third time i decided to use a stronger bolt grade. It stayed in a little longer but still ended up breaking. So whenever it breaks it causes the belt to come lose. Car still works fine but it creates a loud squeaking noise kinda (Its a mix between stepping a small dog and nails on chalkboard) I have used lock tight. Its a pain in the arse to replace beacause i have to remove the alternator and then the blue holder underneath it. I then have to drill the bolt out.

[hls30.com]

Sounds like you have a fundamental harmonic issue at that point of attachment,and probably some previous accident damage that is causing it.

Will

[Arne]

Another possibility is that the bolt in question is not tightening down properly. For example, if the bolt was slightly too long, it might bottom out before it really tightens against the head. In that case, without the stretch-effect of torquing it down correctly, it would back itself out with steady vibration.

You might try an extra flat washer just to make certain this isn't happening.

[Zs-ondabrain]

I'm thinking LOCK WASHER. anyone else?

[Mikes Z car]

I don't know if this might be related but I remember I had an old triumph GT6 once that had a warped brake rotor on a rear wheel so that one of the four wheel nuts would never quite seat the rotor or whatever it is called against the metal plate the studs bolts were mounted in. Eventually three bolts snapped off all at once and I had to put new ones in sitting on the ground in a parking lot getting bad vibes from a nearby proprietor of a doctor's office. Maybe try a different mounting arm in case it is warped somehow?

Mike

[stevef1972z]

I am one for the lock washer, and locktight in combination with Arne's idea of a flat washer and the proper length bolt. After all of the work you have done in the area, I would also run a thread chaser through the threads to clean them up.

Is anything else loosing up? Is there a vibration in the fan from a bad clutch that is making it loosen up? Does the belt dance around and vibrate when it is all replaced and working? How is the alignment, is the belt hitting the pulleys the way it needs to?

[five&dime]

Are you talking about the alt bracket itself ( where the alt bolts to bracket) or the 3 threaded holes that go into the block?

[cglomstad]

thanks to all.

it is actually the 2 bolts which attach the alternator to the bracket that mounts to the block. 4 bolts have snapped and 2 have backed out.Just redid today. Locktite and lock washers. The fan belt comes to the alternator at a a very slight angle.

Could that cause vibration that later results in shearing of bolts? I am sure the bolts are the right length. (I am responding for my son who originally posted)

[doradox]

Does the alternator fit the bracket with no gaps between the ears and the bracket? Are the surfaces that mate flat and parallel?

Steve

[cglomstad]

The alternator fits nicely into the bracket as did the original. It seems to be a tight fit.

The arm which allows for tightening of the fan belt does not line up perfectly with the alternator and has about a 1/2 to 1/4 inch gap which closes when bolt is tightened.

In addition it has now developed a whine after replacing bolts. Have not driven but just run engine in driveway. Not a belt screech but may replace anyway