alternator nut unscrews itself!

alfesti

alfesti

Member
On the V8, has anyone else had trouble with the alternator pulley nut unscrewing itself when the engine runs :?

Its happened a couple of times now, first up in Lincolnshire I heard a squealing sound and stopped just in time to stop the pulley and fan vanishing into a ditch. Nice stranger in an E Type lent me the spanner from his orginal tool kit to get me home (I posted it straight back!) and all was fine for a while.

Servicing it a while later, the nut was loose.

This week the squealing returned, I shut down quick, but the nut had vanished. Got a replacement today and fitted it, but it unscrews within a minute of starting up.

Not sure I trust just locktite. The alternator was an exchange item from one of our 3 usual and reputable suppliers (forget which one) but has it possible its got the wrong direction thread?

Any ideas welcome, havnt driven the car in 3 years and was loving the 3 days I had in it!
 
You wouldn't by any chance have a mixed metric and imperial nut and bolt? I forget which way round it is but if you can wiggle the nut it is a good sign.

Colin
 
Hi, correct me if i am wrong, but shouldn't the alternator pulley be located on the shaft with a woodruff key? This stops the pulley from turning on the shaft. If the key is missing, then this would account for the issue you are experiencing.
It is very easy to overlook when swapping pulleys over during an alternator overhaul / replacement.
Glen. :twisted:
 
Thanks for the ideas, but its definately the right thread, and as Im on the 2nd nut, which me and the chap in the motor factors tried, theres no woodruff key or any kind of grub screw. I was going to drill a hole for a split pi, but theres barely 1mm of thread protruding.

Ive used locktite and left it to cure. If no ones heard of opposite threaded alternators - I guess all engines turn the same rotation - if it fails again I'll have to weld it!
 
alfesti said:
...theres no woodruff key or any kind of grub screw.
Click to expand...

:shock:

Can't say I've ever come across an alternator without some means of transferring the drive positively from the pulley.

Just for reference the shaft thread on the Lucas 18ACR is 9/16" UNF, the nut being 13/16" A/F.

Good luck with it, but I can't see Loctite doing the trick permanently.
 
Hi, when looking at the alternator shaft where the pulley slides on, there should be a groove machined in the shaft to accept a woodruff key.
Also, when looking at the inside of the pulley (the face which contacts the alternator shaft), there should also be a machined groove to locate the shaft to the pulley. The presence of the key is to enable the pulley to transfer drive to the alternator. All the nut does is to stop the pulley sliding off, not turning.
I find it confusing as to why you mention that there is no key. There must be some physical method of locating the pulley to the shaft, or else everyone elses alternator pulleys worldwide would wind the securing nuts off.
The key should be of a semi circular shape.
Glen. :shock:
 
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