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

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 pump. 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. The tube routing looks like this.  I hope you can understand it.             |-- RF door LF --T------+-- RR door LR --|      |             |             |-- Fuel door    Trunk ---|             Pump Defacto wrote: 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 "Herbert Hammer" < snipped-for-privacy@peoplepc.com wrote in message news: snipped-for-privacy@corp.supernews.com...

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

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

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

-Kent

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