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+--- Thread: Vacuum Locking System (/showthread.php?tid=3305)
Vacuum Locking System - sassparilla_kid - 01-28-2012
Okay so I decided to try to get the vacuum locking/unlocking system working because I figured it might be kind of nice to have it in working order. What I have done so far:
-tested vacuum tank, holds vacuum
-tested all LOCKING vacuum lines, all hold vacuum and all doors lock, as well as the trunk and filler flap, when vacuum is applied to the main locking line
-tested UNLOCKING lines, rear doors both leak and do not unlock, front passenger door unlocks and holds vacuum when I test from the line under the front passenger carpet, as well as the trunk unlock also works and holds vacuum
-disconnected and plugged lines for unlocking rear doors, applied vacuum to the unlocking line that goes from front driver's side to passenger's side, does not hold vacuum
Can anybody help me figure out why when I apply vacuum to unlock the passenger door and trunk directly to those lines they work, but when I apply vacuum to the line that goes to the connector they do not? The connectors look good and aren't cracked or anything and seem to hold, so why does it work from one side, but not from the other? I am really puzzled
It seems like the leak is somewhere between the front seats, but I can't really imagine a line breaking there since it doesn't seem like it would get any wear or anything, or am I mistaken? It wants to hold vacuum but its not
Thanks folks!
RE: Vacuum Locking System - bmwpowere36m3 - 01-28-2012
You have to work systematically and trace the leaks to the source... I went through this same sh*t, I think every W123 has. I checked:
- Vacuum reservoir (at line in the engine compartment), takes a lot of pumps!
- Check valve, i.e. only allows vacuum to pass one-way (the yellow one in the engine compartment)
- Each actuator (might as well check all of them, even if they work, because they could still be leaking; thus preventing the rest of the system from operating at 100%)
- Each vacuum line (work back from each actuator, testing both lines whenever they make a rubber connection)
I doubt the plastic line is cracked, both you can cap one end and pull vacuum on the other to make sure... easy enough.
In my car it was mostly the short rubber connections between the plastic line and actuator/check valve/vacuum lock switch. Also one of the check valves failed and my locks wouldn't work.
RE: Vacuum Locking System - sassparilla_kid - 01-29-2012
Haha yeah there are too many yellow lines with multi-colored stripes going every which way!! I have labeled them all though so I know which is which, now I just have to figure out why the unlocking lines do not hold vacuum as a whole, but they do individually. All the rubber connectors seem okay but I guess I will have to take them off and check them all
RE: Vacuum Locking System - Greazzer - 01-29-2012
Yup -- what BMWPower said. My best luck was starting from the vacuum pump and working backwards. A good hand held vacuum pump to figure out where the leak is. The "master" switch in the front driver's door and the black and white check valves were my culprits on top of the dash pods. Excluding the lines and junk in the engine bay, you got the master switch in the front door, a check valve there too. There are vacuum pods in each of the 3 remaining doors for the locks. Trunk and gas flap door and vacuum resevoir by the fuel tank. What I did to isolate the leak was to block off the lines after they left the front passanger's door. That way I knew that everything coming from the driver's firewall thru the circuit before it went back into the dash was OK. There is a new post and threads and some old ones on PP which have all sorts of color coded diagrams, charts, you name it. So much time, energy, and engineering devoted to such a system.