On first (cold) start I get a very high pitched buzz or whine that seems to be coming from the EGR shutoff valve on my 1997 E320. Although it could be coming from another location, it's loudest on the valve (listening through a stethoscope). The part number stamped on the valve is A002 140 25 60.

The buzz lasts for about 60-70 seconds, then the engine goes into a normal idle and everything sounds and runs fine. There is no check engine light, and the engine runs and idles smoothly when warm.

The buzz can sometimes be loud (maybe a ripped diaphragm/vacuum vibration type noise--if that makes sense?).

I'm wondering if this is an issue anyone has come across before, and if there is anything a DIYer can service/rebuild in respects to the valve. The new part lists for $404 (and I'm not inclined to shotgun parts at the issue until I can figure out what the latent problem is).

Thanks for any info.

Pull a hand vac on it and see if it holds vac.

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A Dalton

It goes away after 60-70 seconds? It sounds to me like it's the Air Injection pump running through it's normal cold-start cycle. Try pulling the fuse for the pump and see if the noise goes away.

Okay, I'll look for the fuse and pull it to see. If you have a location/number I'd appreciate it.

The noise is not normal; is the sound I described consistent with the air injection pump failing? Does this pump shut off after the cold-start cycle is complete?

Thanks to ILUVMILS, I was put on the correct track. It is indeed the Air Injection pump. I put the car on ramps, did a cold start and was able to pinpoint where the sound was coming from. So now (knowing the price of a new pump) is there anything serviceable, or do I need to get a whole rebuilt unit. It sounds like the bearings are going out. Should I wait till it fails catastrophically and throws a code, or should I be proactive?

TIA.

I think that once you find out how much a new pump costs, your question will answer itself!!!