Alternator Belt snapped again

adsmx547 · 21 January 2020 23:46

OK, sorry if this has been covered before in other posts but cannot find any that cover this.

My Alternator belt has just snapped again for the second time. The 2 new belts were fitted about a month ago but I had not re tightened them since that fitting.

The front belt is still in place at present but I will replace both as I did before.

I had a quick look today just before it got dark outside and noticed, or think I did, the alternator pulley does not seem to lineup with the crank pulley, is this the reason for the failure?

Is this possible that my alternator not fitted/positioned correctly?

Thanks guys.

rhino666 · 22 January 2020 00:27

If the pulley were not lined up there would be issue as belt would likely abrade on the pulley edges. Just can’t see how this could happen if correct alternator fitted.

Crank pulley is obviously in a fixed position. In order for the correct alternator to be fitted, the alternator pivot wings need to fit either side of the pivot block on the engine, so no room for error there. You have a ribbed pulley that fits straight to the top case half with no extra spacer, so if correct part fitted there will be no issue.

The usual problem with these is alternator partial seizure which stretches and breaks the belt. This is caused by corrosion, mainly galvanic between the four steel case bolts and aluminium case halves. Corrosion causes the aluminium around these bolts to split and starts to take the armature off centre to the field coils as the damage worsens. This eventually allows contact and the potential for seizure. Have a good look at the alternator which if original will be a Hitachi LR180 80 amp. The splits may not be easy to see when alternator fitted. I would advise removing it to have a really good look.

Put up pictures if in any doubt. I used to refurbish a lot of these MK2/MK2.5 original Hitachi alternators but stopped as it got too depressing as had to scrap an increasing number as not in good enough condition to sell, especially with a guarantee.

adsmx547 · 22 January 2020 18:30

rhino666:

If the pulley were not lined up there would be issue as belt would likely abrade on the pulley edges. Just can’t see how this could happen if correct alternator fitted.

Crank pulley is obviously in a fixed position. In order for the correct alternator to be fitted, the alternator pivot wings need to fit either side of the pivot block on the engine, so no room for error there. You have a ribbed pulley that fits straight to the top case half with no extra spacer, so if correct part fitted there will be no issue.

The usual problem with these is alternator partial seizure which stretches and breaks the belt. This is caused by corrosion, mainly galvanic between the four steel case bolts and aluminium case halves. Corrosion causes the aluminium around these bolts to split and starts to take the armature off centre to the field coils as the damage worsens. This eventually allows contact and the potential for seizure. Have a good look at the alternator which if original will be a Hitachi LR180 80 amp. The splits may not be easy to see when alternator fitted. I would advise removing it to have a really good look.

Put up pictures if in any doubt. I used to refurbish a lot of these MK2/MK2.5 original Hitachi alternators but stopped as it got too depressing as had to scrap an increasing number as not in good enough condition to sell, especially with a guarantee.

Thanks for that, as the car is now not being used due to a couple of things needed I will completely remove the alternator and check it over. Many Thanks for the heads up.