ML-320 high pitched noise

Immediately after starting my ML-320 when it's cold I hear a fairly loud, high pitched and steady tone which appears to come from either under the dash or the engine compartment. When the engine warms up this
"tone" stops abruptly as if it was switched off. The noise may not re-appear until the next morning. Of course I can't make it occur when I have driven to the dealer.
I don't think it's a fan that is making the noise.
Any thoughts would be appreciated.
Thanks,
Boden
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I am not fully sure for ML-320 (112 engine), but if it is like its preceder (104 engine) this is as it should be.
In the first minute or so, an airpump will be activated to blow air through the engine block and into the air intake to remove internal vapors (antipollution).
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In boden typed:

See http://tinyurl.com/qesw6 & http://tinyurl.com/n69bp
DanlK, ~~~\8-O FYI Services Collectibles www.FYIS.org
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Just for the information of it, does this blower also ventilate the engine initially after start ?
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No, it is a tiny little blower in the fuse box.

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Thanks all for the help. I'll take the fan out and try to get a replacement. Since the nearest MB dealer is now 3 hrs away and he doesn't stock many repair parts I may need to wait to replace the fan. Claire has been my salvation lately. If I need a replacement they may have one.
Boden
boden wrote:

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