Hello all, the EGR pressure converter valve on my 1984 300 Turbo seems to run (make noise) for about two minutes after I shut the car off. This is the valve hanging on the right front inner fender under the hood behind the headlight.

I've been searching quite a bit and can't seem to figure out why! Any insight would be greatly appreciated.

It has a vacuum diaphragm in it that's likely leaking. What you're hearing is probably the vacuum bleeding down.

Block off the vacuum line coming to it from the vacuum pump with a BB or ball bearing and don't lose any sleep over it.

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

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1986 300SDL (RIP)
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1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]

That's exactly correct (except the part about blocking the line). The valves often don't completely seal at shutdown, and they allow the vacuum to gradually bleed down. I'm not sure why this is, but I've gone through several used transducers and they all have the same behavior. Despite this apparent leak, they do work correctly when everything is energized.

You are both correct, I verified and it's definitely vacuum leaking down. As long as it doesn't represent a leak during operation, I suppose I'll just disregard! Or perhaps an excuse to disable the EGR in its entirety.

P.S. Thanks for the quick responses, I guess peachparts will be my new go-to. My benzworld post fell on deaf ears!

There's really no reason to do that. I should have added that the way to test the function of the transducer (and the entire EGR control system) is to add a "T" to the EGR vacuum line. Run a temporary vacuum gauge off the T and bring it into the cabin through the passenger window. Whey you drive, EGR should be near zero at idle or at full throttle. The only place you will have peak EGR vacuum is at steady cruise. This tells you that the EGR system has minimal impact on performance. It's turned off as soon as you get on the pedal.