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Old 09-13-2007, 03:40 PM   #4 (permalink)
gregs210
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Date registered: Mar 2005
Vehicle: '01-E320 & 02-ST2
Location: Adrift on an island...
Posts: 7,064
Quote:
Originally Posted by MBCoupe
The alternator my 1994 E320 Coupe makes a whirring sound and will not go away at any speed. Is this a sign of a major problem about to happen?

Thus far the battery remains fully charged and all electrical systems are working. There is no perceptible dimming of the headlights even at idle speed.

Should I take action to replace the alternator now, or will there be a more definitive warning before it fails altogether.

What's the best course of action. Thanks for insights. advise or comment.
Hey, MB.

That sound is probably the bearings. If you're good you can just order the brushes and bearings and rebuild it yourself, not too tough at all. Otherwise I would suggest you go ahead and replace it now, you can buy bosch rebuilds with a good warranty on them. If the bearings freeze it will burn up the belt and perhaps strand you.

One other thought, are you 100% sure the noise is coming from the alternator? To confirm you can remove the belt and spin the pulley by hand, or if you have clearance and you're very, very careful, use a long piece of hose (vacuum line is ideal) and insert one end to the edge of your ear canal and hold the other by the alternator, carefully avoiding the belt, fan, etc.

Take care and enjoy the ride,
Greg
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