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  #1  
Old 03-21-2002, 04:47 PM
Holson Adi's Avatar
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Vacuum failed but works after car is started?

Just yesterday the locks stopped working and I couldn't open all the doors by just opening one door.

I'm not sure if the water had anything to do with it. However it did rain for almost two days non-stop in Boston.

The weird thing is that the vacuum would all work after I start the car for a while. It would still work even after I kill the engine. Until a point where there would be no more vacuum...

I know that the car leaks from here and there. However, I hope nothing major went wrong.

Any ideas?
Could it be the vacuum tank?

Before the stupid rain+snow everything worked perfectly.

Thanks
-Holson-

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Old 03-21-2002, 05:02 PM
jcd jcd is offline
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I have the same thing.........

I have been afraid to diagnose this leak in the cold weather as the vacuum hoses are very brittle. Past similar incidents have proven to be either a small leak in the vacuum hose, or a failure in one of the door lock vacuum gasket/actuators. Mine exhibits similar symptoms as yours and rain, sleet, snow had nothing to do with it.

I would wait until the weather gets warm and get out the MityVac.

JCD
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Old 03-21-2002, 07:16 PM
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My money is on one, or more, of the top diaphram from the door acuators. Even though they are inside the door, they are exposed to the elements and tend to let go before the lower diaphrams do.
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Old 03-21-2002, 07:25 PM
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What's a MityVac?
Is it a vacuum leak diagnosis tool?

What worries me is that the car did not do this before the snow,etc. hit.
Everything worked great no matter how long I left it sitting.
Wonder if I should overhaul the whole vacuum system..
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Old 03-21-2002, 07:47 PM
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I guess this can wait until summer (since it at least locking works.. it just doesn't really unlock everything... )

I just read through the manual.
Is the vacuum switch an electrical device?
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Old 03-21-2002, 07:49 PM
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Cool

My money is on either the trunk lock vacuum element or the gas door element...the more vacuum hoses you replace, the better. I don't own a mighty vac but when one of these elements fails, I have a way of testing. When the car has full vacuum pressure(Running if there is a leak), try and lock or unlock the doors by hand. It should be fairly difficult to do. If one of the locks goes up or down easy, that is probably the culprit. Same for the gas cap or trunk lock but some minor disassembly is needed to reach these two. Once you have a suspect, the real test is holding your finger over the hole and try and operate the vacuum cylinder. If you can move the cylinder at ALL, then it's the culprit. Try both holes. If the element is in good shape, it should be next to impossible to push or pull the cylinder when your finger is over the appropriate hole, one for one direction one one for the other. I hope this helps.
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Old 03-22-2002, 01:15 AM
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Holson,

If it is one of the door actuators you really don't want to let it sit unattended too long. In the locked position the diaphram is drawn down, creating a shallow depression. If the diaphram has a hole in it, any water or dirt accumulating in the depression can be drawn into the vacuum system if it gets inside the actuator (and if there is a hole it will get inside the actuator). Granted it would be a small amount, but who wants that crud on the inside of the system?

The master vacuum switch in the driver's door is not an electrical switch on your car. It is a simple vacuum directional switch - very seldom go bad. Not a bad idea to change all the rubber connectors to the switch and actuators as you go about finding the bad diaphram.

Some actuators can be rebuilt, like on the 108, but 123's are a sealed unit and the entire actuator has to be replaced. If you find one bad, I will pass on advice I was given and didn't heed - change them all (3 of them on a 4 door). If you don't in a short time you'll be trouble shooting the system again because one of the ones you didn't change went bad.

I just noticed your talking about a CD. You only have one actuator in the passenger door, the trunk lock and the fuel door. That makes finding the culprit somewhat easier.
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Last edited by MikeTangas; 03-22-2002 at 01:21 AM.
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Old 03-22-2002, 09:08 AM
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How easy a job is it?
Let's say that I can't be bothered to find the culprit and I just wanna replace all of 'em with new ones (It doesn't matter, it's an old car anyway)

Which parts do I need?

If it's not an easy job I think I'm just gonna let the shop do it.

Thanks
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Old 03-22-2002, 01:55 PM
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I didn't find it all that difficult. There is only minor disassembly involved. The door panels come off easy by prying gently near the clips after making sure all of the armrest and door latch screws are out. The vacuum elements themselves are held on by 1 or 2 10mm nuts and two vacuum hoses. When reassembling the door panels, make sure the weather strip on the top fits snugly and snaps back into place. To get to the fuel door, you just have to move the plastic trunk liner out of the way and for the trunk lock, there is a small plastic plate that comes off next to the trunk lock assembly. To do them all you need is 3 doorlock elements (not including the master in the drivers door), trunk lock and gas door elements and maybe an assortment of rubber tees and elbows where the hard plastic vac lines join up. I'm not sure how many though roughly 2 tees for each door, 2 tees for fuel door, and 2 elbows for trunk lock.
Could be finished in a couple of hours.
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Old 03-22-2002, 04:14 PM
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That sounds like fun *I'm serious*. I'm gonna order the parts from Fastlane but maybe only in summer or late spring...
or whenever it's not 25F out there (I love Boston's weather in spring! )

I guess I'll just save this thread onto a word document when it finally sinks down the thread list.

Thanks a lot guys BTW, really helpful. At least I know that it isn't anything funky (electricals, etc.)

I did the rear window seal today. The glass shop guy didn't even break a sweat doing it. The guy knew exactly what he was doing. He's actually done many of these W123's. I asked one shop and the guy pretty much told me to go to the MB dealer....

Just another question,

Could it be one of the vacuum lines that work to lock the seats in place? (The coupe has this thing that you press on the seat to quickly fold the backrest..) I think it works on the vacuum too...
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Last edited by Holson Adi; 03-22-2002 at 05:35 PM.
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Old 03-23-2002, 05:58 PM
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Update:

To get myself familiar with the vacuum stuff, I took a look at the trunk and the fuel door ones.

The vacuum elements look like a tube don't they?
The diaphrams are the red rubber thing that looks like it seals the tank and whatever shaft or line runs through it, aren't they?

I also noticed those rubber lines. Are they available in any auto store? Because I looked in Fastlane and I couldn't find anything...
I guess I also saw the 'tee's in the trunk vacuum element.

It doesn't look that hard to fix. I have ordered the diaphrams from Fastlane and when they arrive, I'll just get working on it (I have a rather easy week coming up, which is good for the 300CD)

I can't believe that a shop quoted me $560 to replace all the diaphrams... I'd be rich if I could make $400 just installing diaphrams... (if i know how to do it)

I hope I can fix it myself.. otherwise I'll just bring the diaphrams to a shop and ask 'em to install 'em for me.

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