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