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?Alternator Whine? - Engine/Ancilliaries - The Lotus Forums Jump to content
slewthy

?Alternator Whine?

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For as long as I can recall, my S3 has always made a whine on engine revs.

I had assumed (without actually thinking) it could be the differential and since everything worked, ignored it in an ostrich type of way.

However, this afternoon whilst driving it occurred to me that it could be the alternator.

The whine is related to engine speed, not to car speed - if I depress clutch, and press on the gas, the whine increases in pitch and vice versa.

So, how to test the theory without having to slacken off the alternator, which is less accessible than I recall. 

I'm guessing its an under the car job, slacken and see? But before I do that does anyone have any alternative (pun intended) ideas?

 

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Cambelt whine? (too tight or blue Gates Racing belt)

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Thats a possibility although I'm pretty sure its been present with all 3 standards belts I've had. Tensioner has been rebuilt and tension tested in a couple of ways - twist and frequency.

I'll check it though - thanks

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I've heard plenty of standard-belt Esprits produce whine. They were just set too tight. (Many shops don't have the tension gauges or know how to properly do the frequency check)

 

You COULD just mark the alternator position on the lower strap (the plastic one on a Turbo). It's EASY to loosen but more difficult to tension, if that's not the source.

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Yes, think thats the best way to eliminate or confirm.

Question is, if its the Cambelt, I have an automatic tensioner, so where would the issue be?

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If the whine changes when the alternator is loaded ie turn on main beam, it probably confirms the alternator.

 

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If the cambelt has been changed a couple of times and the whine stays the same, it's less likely to be a belt. The alternator belt would have been replaced or at least removed and refitted each time as well. So I'd look at the tensioner and pulley bearings (including those of the alternator).

Filip

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17 hours ago, slewthy said:

 I have an automatic tensioner, so where would the issue be?

The automatic tensioner is only semi automatic!   It does not prevent either under tensioning or over tensioning.   It needs setting on changing belts and should be checked periodically.   My hunch is that it was originally designed to allow between cold & hot engine, which has a significant impact on th belt tension.   As CarBuff says, an overtensioned cambelt will whine.  

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22 minutes ago, 910Esprit said:

The automatic tensioner is only semi automatic!   It does not prevent either under tensioning or over tensioning.   It needs setting on changing belts and should be checked periodically.   My hunch is that it was originally designed to allow between cold & hot engine, which has a significant impact on th belt tension.   As CarBuff says, an overtensioned cambelt will whine.  

Your hunch is correct! The first engines supplied to Jensen had manual tensoners but they found the belt jumped teeth when the engine was very cold or on the other hand it would be too tight when hot. The spring tensioner was a hurriedly-designed mod.

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