There is some noise coming from my hood that sounds like a jet engine is stuck in it. When opening it the sound comes from the left near the belt.

I figure that it's either the air pump or the alternator. After reading several past posts I think it's the air pump. I've never heard of an alternator making noise like this. The noise is always on and is louder than the usual air pump start up noise which can be heard also at start up when cold. So my first question is, which is it, the alternator or smog pump? I think smog pump.

If it's going bad and I choose to just take it off completely does anyone know what belt length I need to buy and where I could find out?

Will I have any trouble with the SMOG inspection, the visual aspect? Has anyone ever had this job and can say how detailed they look at the engine?

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1992 Mercedes-Benz 400E
2002 Mercedes-Benz ML500