Hey Guys,

My '91 300E has developed a weird whine noise when she's cold: it's a metallic whine that almost sounds more like a whistle, that only happens when you increase or decrease RPMs. The noise is based in or near the Smog Pump. If you rev the engine a little in Park while touching the Smog Pump you can actually "feel" the whistle if you get my meaning.

Can anyone educate me on the Smog Pump? How does it work/When does it work/What does it affect electronically & atmospherically (where it goes into the manifold)? There's nothing in any of my books...

Has anyone ever gutted one (if this actually is my problem)? You have to leave it in due to the damn serpentine belt...

Any info would be greatly appreciated!

Thanks!

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Currently:
1972 350SL Euro 4spd
1973 BMW R75/5
1981 BMW R80GS
1995 FZJ80 with OM606 Conversion In Progress