84 733i crank shaft

The nut on my 84 733i crank shaft pulley came off and of coarse all the belts stopped. I got another nut and washer and put it on as tight as I could by hammering on the socket handle. The pulley would turn and I
hammered some more. But the nut comes loose after a minute of running. How can I keep the nut on? Larry
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L. D. Mormino wrote:

Take the pulley off and replace the key that fell out or sheared off.
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My book does not show a key and the BMW parts person did know of one when I bought the nut and washer. I understand that it is a tapered fit. Larry

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Not sure about this model, but they're generally a woodruff key. This is a sort of D shaped device which is a tight fit in a matching keyway. The idea is it is self aligning as you slide the pulley on. If the nut came loose, the pulley should still have turned - unless it came off the key. If the nut had been loose for some time the key may have sheared off. The nut or bolt should secure the pulley tight against the collar on the crank, but it's the key which does the work of driving the pulley - not friction. It things came loose and are left for long you'll need to check the nut is actually 'nipping' up the pulley and that the key and keyways are still in good condition.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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I got the crack shaft pulley off and to my surprise the hub was broken at the key way. The crack shaft end looks great but the key, nut, and washer were gone. I was able to take off the pulley without taking the radiator out but removing the fan, and belts. Now I am looking for a hub for the crack shaft pulley.

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