Old style vacuum door lock actuator repair. - PeachParts Mercedes-Benz Forum

fender_bender · #1 03-21-2013, 11:43 PM

Hello all. I recently had a vacuum leak in my door locks that I traced to the actuator in the front passenger door. The leak was from dry rotted rubber diaphragms or bellows. I found some replacements online for around $10 a piece. Here is how to replace them. Now I don't show how to take the door panel off as it has been shown before. This is extremely easy to do and a heck of a lot cheaper than buying a new actuator. So let's get at it.

This is the actuator at the bottom of the door. Remove the vac lines. Try to remember which one goes where. If you reverse them then it will just operate backwards (unlock when you lock the driver door) These two hex bolts hold it in place. Remove the two bolts to free the actuator from the door.

There is a little C-clip or snap ring that holds the rod to the actuator. I used a magnet tipped flat head to remove it. BE CAREFUL! It is tiny and can shoot off pretty far.

It's a tiny little guy. The actuator is now free from the car.

This..."thing" comes off the actuator just by sliding it off. Mine was on there pretty good so I had to use some vice grips to help me along.

It's off.

These little rings have two tabs that hold them onto the actuator and keep the rubber diaphragm from popping off.

The old diaphragms were so bad the they just fell apart when I pulled on them, but you can run a small screw driver under the lip at the bottom and they just come right off.

I flattened the new diaphragm out a bit and set it on the actuator and just kinda unrolled them over the lip. It took both hands and some stretching to get them to "seat"

After they are installed plug the vac nipple with your finger and push down on one of the diaphragms. You should see the other one bulge and no air should leak out. Test both. Then replace the plastic rings over them. Now you have a working door lock actuator!

I used my vice grips to pinch the diaphragms back onto the "thing". Then I put the rod back into the top of the "thing" and bolted the actuator back into the door. Now for the C-clip.

Take some needle nose pliers and grip the back of the C-clip tightly and push it into place. Replace your vac lines back on the actuator and replace the door panel and that's it! I tested my locks before door re-assembly just to be safe.

I hope this helps you get your actuator working again! It's SO much cheaper than buying a new actuator and gave me a chance to lube some of the door internals while the panel was off.

bricktron · #2 03-21-2013, 11:56 PM

very nice work. who was the vendor? did you get a part number?

fender_bender · #3 03-22-2013, 12:25 AM

Quote:

Originally Posted by bricktron

very nice work. who was the vendor? did you get a part number?

It was Mercedes source. They didn't have a part number listed. I forgot to look on the actual part!

.

zeke · #4 03-22-2013, 12:44 AM

Thank you for posting this!

fender_bender · #5 03-22-2013, 09:01 AM

Quote:

Originally Posted by zeke

Thank you for posting this!

No prob!

They have a kit on mercedes source that comes with 4 diaphragms, instructions and I think some sort of grease for under $45. I only need 2 so I just bought the individual ones. I'm not sure if the grease is real important I'm just a DIY guy and this mercedes is the first car I ever worked on or even wanted to work on. I used to just take my other cars to the pros, but now I can screw up my mercedes all by myself! I will say Msource shipped fast and they put a pair of gloves ini the box and a lemon head candy, which my great dane promptly ate without permission...BAD DOG!

WrightSounds · #6 03-22-2013, 11:27 AM

Nice pics and thanks for the source! Did you replace all four on that signle actuator or just the "top" two? I'm wondering if you were able to tell if just the top two were leaking?

Thanks again for the great pics and tutorial. I'm in the same boat as you... my 1980 300SD is the first car I've ever worked on. And right now I'm in the middle of a door lock/window fail mess

Stevo · #7 03-22-2013, 12:10 PM

My 79 has not had a vacuum pod failure yet but I have the spare billows and now I have instructions on installing them when the time comes. So thanks

Biodiesel300TD · #8 03-22-2013, 12:12 PM

Quote:

Originally Posted by WrightSounds

Nice pics and thanks for the source! Did you replace all four on that signle actuator or just the "top" two? I'm wondering if you were able to tell if just the top two were leaking?

It's usually pretty easy to find the cracks or tears in the diaphragms just by looking at them. But if you test each side with a mity vac you'll know which ones need to be replaced. Often with the the mity vac if only one of the diaphragms is leaking on one side, the leaky one won't suck down but the good one will. I always snag these out of the junk yards, you can get piles of them for cheap.

Good write up. I can't tell you how many door lock actuators I've had to repair or replace over the years with my 123s.

fender_bender · #9 03-22-2013, 10:39 PM

Quote:

Originally Posted by WrightSounds

Nice pics and thanks for the source! Did you replace all four on that signle actuator or just the "top" two? I'm wondering if you were able to tell if just the top two were leaking?

Thanks again for the great pics and tutorial. I'm in the same boat as you... my 1980 300SD is the first car I've ever worked on. And right now I'm in the middle of a door lock/window fail mess

I only replaced the top two. They were leaking and I could see cracks from the dry rot. I did a simple test with out the mighty vac even though I have one I didn't want to go get it

. I just plugged one of the nipples (the closest one to the diaphragms you're testing) with my finger and pushed one of the diaphragms down. It went "PSSSHHHH" and I knew they were leaking. The bottom 2 were fine and looked like they had been replaced before.