M.B 240D Vacuum Central UnLocking

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2 replies [Last post]
monarchd's picture


Hello!!! This is the first time around, and it seems to be an awesome webpage for M.B lovers.
I have two questions for my 1981 240D.
It won`t unlock the doors even with the engine running. You have to manually unlock each door.
And the second, It will only lock all 4 doors if the engine is running. If it`s off, it won´t lock them.
When it´s on, they all lock perfectly fine. I understand that all doors should lock and unlock with the engine on, and do the same for a while after it has been turned off. Can anyone help out here?

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Former Member
Garlynn's picture
Joined: January 5th, 2007


Re: M.B 240D Vacuum Central UnLocking

dunno if you're still reading this thread, but... I'm proud to report that, when we purchased Gladys (1983 300D turbo, same locks as yours), she had no central locking capabilities. However, as of this past weekend -- she does. I had to get an interior panel removal tool (about $10 at the local auto parts store), and with that I took off all four door panels, one at a time, and checked the condition of the vacuum elements in each one. I previously owned a vacuum tester (these are a must-have for these cars, you should find one, they're a worthwhile tool to have), which I used to test that the vacuum reservoir in the trunk holds vacuum pressure. I also used it to check the trunk and fuel flap vacuum elements.

I diagnosed that the right two doors had rotten rubber in their vacuum elements, and ordered new replacements from Rusty. When they arrived, I replaced them -- and now Gladys had functional central locking again!!!

It's really a simple system, and the fix is easy. It was $30 per vacuum element. From your symptoms, I bet you have just a minor leak somewhere in your system. Maybe just the rubber on one door is starting to go. That'll be about $35 or maybe $45 with shipping if you're overseas.

Best of luck.


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