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1982 300SD 126
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7 Posts
Discussion Starter #1
I have a 1982 300SD and the driver door can't be locked either by pushing down the lock or with key. All other 3 doors lock fine. My impression seems that it's built up vacuum at the lock. The door did lock at one time when I first had the car, but only after some vacuum had bled off at the door lock. The vacuum system on this vehicle isn't my strong suit, so this is just my impression based on what I've seen over the years.

Appreciate any help you can give me on troubleshooting this.

Thanks,
John
 

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Premium Member
2012 CL550 4MATIC Coupe
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9,992 Posts
I have done a couple of write-ups on the vacuum locking system in the past. Look in the archives. What it sounds like is that the vacuum "Element" in the door has gone bad. What the element is, is a vacuum operated servo mechanism. There is a vacuum pump in the trunk, in the spare well. It fires off when the buttons are cycled or the key is cycled. You should be able to hear the pump with the trunk open. It's encased in a rubber boot.

The door elements (as well as the ones for the A/C in the dash) have a rubber diaphragm in there that dries up and goes bad and starts to leak. Once that happens, proper vacuum cannot be maintained and the system fails.

You will need to open the door panel, take apart the element and replace it with a new one. This after you check proper operation of the pump first.

PM Me your email and I will point you to the manuals.

M
 
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