lock system leak - between yellow splitter and driver's door - PeachParts Mercedes-Benz Forum

kuene · #1 05-23-2017, 02:01 PM

Hi. I've become quite intimate with my vacuum system. Yet I have a leak and I cannot locate the exact source.

Removing all other systems and testing both the pump and the brake booster - I'm confident this is within the locks, and unrelated to climate, shutoff, VCV, etc.

I've also tested the lines branching off from the driver's floor to the rest of the doors, trunk, and gas lid. We're good there, and I've tested the storage tank too.

I've isolated the vacuum leak to somewhere between the driver's door master element, and the yellow splitter/check valve on the other side of the firewall. I've been inside my door and tested the master element. I've tested the yellow check valve. Both are fine.

When i shut off my car, there is a clear whine (that I have confirmed is directly connected to the leak) that seems to come from somewhere behind the dash/kick/cluster area. If I quickly lock the car, the whine stops, and I have plenty of vacuum stored to unlock the car an hour later. When idling with no radio noise, you can also hear this whine. When I remove the lock branch from within the engine bay, the whine is gone.

this diagram indicates a check valve somewhere in the dash area, after the yellow splitter valve in the engine bay, and before the door elements.

I believe this is where the leak/whine may be coming from - but I CAN'T SEEM TO FIND THE DANG THING. It's very hard to see with all of the wiring and cabling stuff up behind the dash, and I just cannot begin to guess where this thing is hidden. Has anybody every located this secret check valve? Forgot to mention, this is an 1982 300D turbo.

mikeyfev1 · #2 05-23-2017, 05:48 PM

Quote:

Originally Posted by kuene

I've been inside my door and tested the master element. I've tested the yellow check valve. Both are fine.

When i shut off my car, there is a clear whine (that I have confirmed is directly connected to the leak) that seems to come from somewhere behind the dash/kick/cluster area. If I quickly lock the car, the whine stops, and I have plenty of vacuum stored to unlock the car an hour later. When idling with no radio noise, you can also hear this whine. When I remove the lock branch from within the engine bay, the whine is gone.

this diagram indicates a check valve somewhere in the dash area, after the yellow splitter valve in the engine bay, and before the door elements.

I believe this is where the leak/whine may be coming from - but I CAN'T SEEM TO FIND THE DANG THING. It's very hard to see with all of the wiring and cabling stuff up behind the dash, and I just cannot begin to guess where this thing is hidden. Has anybody every located this secret check valve?

There is a check value in the driver's door, right before the master switch, at least there was in my '85 300D. As I recall it was just a one-way valve.

Others have reported that the hard lines will sometimes split. That would be very hard to find. It usually happens near the door hinges, where the hard lines have to travel/flex between the door and the body.

kuene · #3 05-23-2017, 06:15 PM

I feel like it has to be some sort of busted valve because of the the noise characteristics (or actuator, but in this case it's happening before any actuators). I don't think a cracked hard line would make this kind of whine, it would be fairly silent because there is nothing much to vibrate. This whine has a distinct rubber/diaphragm character to the sound, if that makes any sense - but I could be wrong.

I'm fairly certain there is no check valve in my door, I've been in there once already to test the master element.

kuene · #4 05-23-2017, 06:17 PM

maybe its time i break out the cigarettes and attempt a smoke test? since it's such a small area of the system I'm testing, might it actually work?

1983/300CD · #5 05-24-2017, 05:50 AM

There is a yellow check valve at the center vent, and if I remember correctly from so many years ago when I pulled the dash, I think there is also another (either black or blue?) on the driver's side. Don't quote me on that, though. Unless someone can confirm.

A whining could be a failing connector, though.

kuene · #6 05-24-2017, 11:43 AM

thanks 1983.

I think you are right, it could be a failing rubber connector, but the only rubber connector would be the ones linking the check valve to the hard line, so if I find it I will replace all rubber along with the valve. So this black/blue one you may have seen on driver's side - THAT is the one I'm looking for! Do you think I have to pull the dash? Could I get to it with just the cluster removed perhaps?

1983/300CD · #7 05-24-2017, 07:01 PM

The cluster leaves a big hole, so maybe. You would need to remove the cluster if you were going to pull the dash anyway. I remember it being in the corner on the left side. There's no guarantee that is your problem, though. I don't even remember what line that valve was in.

kuene · #8 05-25-2017, 10:50 AM

Yeah, this is helpful though. Might not be my source but it's a lead.

kuene · #9 05-25-2017, 03:00 PM

link to photo

found this photo of exposed dash. the arrow is pointing to what I think is a check valve on the door lock line (maybe). Anybody else think that could be the case? If I can't get to this with just cluster removed, do you think I might have access through the dash speaker cutout, once speaker is removed?

another shot of it here... looks accessible maybe

kuene · #10 06-07-2017, 02:00 PM

just an update and a question about very slow leak down.

I was able to locate - by feel - this check valve on the main lock vacuum line that is under the dash. It is, at least on my car, inaccessible to test or change out the check valve given where it is positioned. However, I decide to open up my driver's door again and do some more testing. turns out my master lock element DOES have a leak when in the unlocked position - leaks down from 15 to 0 in about 30 seconds. So I went ahead an ordered a new element.

Before I put my instrument cluster back in I tested the line from the yellow splitter point in engine bay, to where it goes into the master door element. It appeared at first to have NO leak. But when I set the mityvac at 15, and left for work - when I returned about 12 hours later the vacuum reading had dropped to 10. So it has a VERY slow leak. Since I can't access this check valve unless I completely remove the dash (which I'm not doing) the only way I could deal with this is by running a new line, around this inaccessible part - which still might be challenging, but doable. Do ya'll think it's worth dealing with a leak of this small magnitude? At home I keep my car in a locked garage, and don't care if the locks loose power after a day or so. When I'm out and about, 12 hours is about as long as I'd ever be away from the car. Seems like I can just live with this tiny leak right?

tyl604 · #11 06-07-2017, 04:52 PM

I would wait a while after you make this repair and see if it is really a problem - or if it is a big enough problem to do something about.

kuene · #12 06-20-2017, 12:50 PM

update if anyone cares. turns out i had a significant leak in my rear left door element. The physical source of the sound, the long whine that lets out when I had the car in unlocked position after turning off engine, was playing tricks on me. So hard to tell where it was coming from - but I finally tested all the lines again and realized there was a huge leak in that door - must have missed this while testing last year, or it developed/got worse. replaced that actuator and now lock system is working very well. probably won't hold vacuum over the course of a couple nights, but good enough for me.

tyl604 · #13 06-20-2017, 01:21 PM

Great. I have an '81 300SD and it holds vac perfectly. I did replace two door actuators maybe six to eight years ago.

tyl604 · #14 06-20-2017, 01:31 PM

Great. I have an '81 300SD and it holds vac perfectly. I did replace two door actuators maybe six to eight years ago.