83 300SD "Lazy Locks"

Recently, my 300 SD's locks intermittently work. When this does occur, its when I try to lock the doors. When depress the driver's lock button, I can
hear the other locks try to go down and move slightly - then nothing. If I depress the passenger door lock - all of the locks go down. Based on some investigating - my thought is that I have a "Vacuum Change Over valve" that is failing. Also, sometimes after I just park the car, I can hear the vacuum pump "whirring" in the truck. Again, I suspect this is due the vacuum leak somewhere in the system.
Has anyone run across this situation? I would like some advice before I tear up the car and pull out the "Mity Vac" to find the leak.
By the way, this newsgroup has been a wonderful resource regarding questions I've have with my MB.
83 300SD - 187255 miles
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According to an eBay vendor, the vacuum pump may need rebuilding, an affordable and relatively easy fix. Check for oil build-up in hoses.
Augie
1982 M-B 300SD 303,000 plus miles

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<!doctype html public "-//w3c//dtd html 4.0 transitional//en"> <html> I think the 83 300SD uses electrical vacuum pump in the trunk to un/lock doors, not the mechanical pump on the engine.&nbsp; The mechanical pump can be rebuilt but I am not aware of any rebuilding kit for the electrical pump. <p>Start the debugging process from the trunk, before tearing the doorpanels.&nbsp; Vacuum locks doors and air pressure unlocks.&nbsp; First see if the pump has enough power.&nbsp; Then use mity-vac to replace the pump to see if you can lock all doors and hold vacuum for a few minutes.&nbsp; If not, test the vacuum branches under front carpets, outwards, probably under a black plastic cover.&nbsp; Test each door one by one.&nbsp; Don't forget fuel door and trunk also have vacuum elements. <p>The tube routing looks like this.&nbsp; I hope you can understand it.<p><tt>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |-- RF door</tt> <br><tt>LF --T------+-- RR door</tt> <br><tt>LR --|&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |</tt><br><tt>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |</tt> <br><tt>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |-- Fuel door</tt> <br><tt>&nbsp;&nbsp; Trunk ---|</tt><br><tt>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Pump</tt> <p>Defacto wrote:<blockquote TYPE=CITE>According to an eBay vendor, the vacuum pump may need rebuilding, <br>an affordable and relatively easy fix. Check for oil build-up in hoses.<p>Augie <p>1982 M-B 300SD&nbsp; 303,000 plus miles
href=" <br>> Recently, my 300 SD's locks intermittently work.&nbsp; When thisdoes occur, <br>its <br>> when I try to lock the doors.&nbsp; When depress the driver's lockbutton, I <br>can <br>> hear the other locks try to go down and move slightly - then nothing.&nbsp;If <br>I <br>> depress the passenger door lock - all of the locks go down.&nbsp;Based on some <br>> investigating - my thought is that I have a "Vacuum Change Over valve"<br>that <br>> is failing.&nbsp; Also, sometimes after I just park the car, I canhear the <br>> vacuum pump "whirring" in the truck.&nbsp; Again, I suspect thisis due the <br>> vacuum leak somewhere in the system.<br>> <br>> Has anyone run across this situation?&nbsp; I would like some advicebefore I <br>> tear up the car and pull out the "Mity Vac" to find the leak.<br>> <br>> By the way, this newsgroup has been a wonderful resource regarding<br>questions <br>> I've have with my MB.<br>> <br>> 83 300SD - 187255 miles<br>> <br>></blockquote> </html>
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Do you have the name of the vendor or the e-mail link?

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The eBay vendor is "mercedessource", he's got a niche market of his own specific parts/instructions. Also check out "buymbparts" for great buys on consumables (filters, Liqui Moly) and parts.
Regards, Augie

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Do you have the name of the vendor or the e-mail link?

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You have found the problem. The passenger door vacuum actuator is leaking. I bet you can hear air leaking if you try.
-Kent
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