Trunk Lock
 

I had a mechanic who took it upon himself to "adjust" the vacuum lock system on my 1981 240D. Granted, one of the locks gets sluggish from time to time, but now I can't open my trunk. I am wondering if it is the vacuum system or the lock itself. Is this something I can check or adjust myself? I am pretty handy for a girl, but not a greasemonkey. How much should the repair cost?
I live in NYC, but now use a fairly good one in Glen Cove, Long Island. Thanks in advance for your help.

By adjusting you vacuum system, I'm going to assume that the vacuum control over the trunk lock was bypassed.

You say you can't open the trunk. Does that mean not even with the key? You should be able to insert the key into the trunk lock, turn it to the left about 30 degrees past horizontal, and push the button in with the key still in the lock. With the button pushed in, then lift the trunk lid.

If you can get this far, then we can guide you through diagnosing problems with the vacuum control. It's so easy, even a girl can do it. ;) But if you can't get the trunk open with the key, then that's a job for a professional.

Trunk lock
 

Thanks so much for your reply. I have tried opening the trunk with the key. That is the only way I can do it, unless there is some secret release latch I don't know about. I was reading with interest another Mercedes owner whose trunk was stuck and coincidently, the A/C was blowing out of the defroster vents. He determined that this was a vacuum problem. I noticed my heat and A/C were coming out of different places around the same time my trunk lock started acting up. So, I thought I'd throw ithe problem out on the net for input.

There is a tube (vacume line) that runs to each of the locks on your car. Chances are that the tube that goes to your trunk lock is no longer pluged into the trunk lock. If this is so then the question becomes: WHY is it disconnected? Was it done so intentionally for a reason or by accident. If it is disconnected try to plug it back in again and then test to see if the trunk locks and unlocks normally. Tell us what you find out.

Ok, open the trunk with the key. On the inside of the trunk just below the latch there is a little access door that you can pop out with a screwdriver. Behind that door is the vacuum pod for the trunk lock.

The pod has two vacuum lines running to it. Both lines are yellow, one has a green stripe, and one has a red stripe. When air is sucked out of the red striped line, the pod locks the trunk. When air is sucked out of the green striped line, the pod unlocks the trunk.

You can test the pod by pulling the yellow lines out from the black rubber hoses, and sucking on the hosed individually. Each one should move the lock rod, and then should not allow any more air to pass through. If they continue to allow air in, then that is a vacuum leak and the pod should be replaced. They are available from Fastlane at the top of the page here.

Of course you can test these vacuum elements by mouth as I've described here, but there's a handy little device called a MityVac which is much better for the job. It has a gauge to measure the vacuum, so you can connect it, pump down the vacuum, and watch the gauge for a leak. You can pick one up at Autozone for around $25.

Let us know what you find out.

Wow! Thanks for your replies! I can't wait to follow your suggestions. Hopefully, I will gain use of my trunk for the 4th of July weekend. I'll keep you posted.