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Vacum Leakage

2K views 7 replies 4 participants last post by  Minnet 
#1 ·
Guys, Ineed Some Guidance On How To Find And Fix A Leak On The Vacum System .
As You May Know The Original ( Halogen ) Head Light Beam Height Is Being Adjusted Manually By A Knob In The Cocpit Via Air Pressure Coming From The Vacum System Of The Doors And Trunk.
After I Had The Original Headlights Changed With The Xenon Ones In The Dealer I Have Started Having Problems With The Close Assist Doors Especially Starting From The Drivers Side Door.when I Reset The Circuit Breaker It Temporarily Solves The Problem But After A While Same Thing Again.
I Know This Is Because The Air Powered Head Light Height Adjustment Is No Longer Working Due To The Different System Of The Xenon Headlights.
Any Body Has Any Idea About Where To Find And How To Fix This Leakage Problem?
 
#2 · (Edited)
First of all, the headligth range adjustment and the close assist operate via two entirely (almost) separate pneumatic systems.

The heigth adjusment operates via manifold vacuum assisted by the central locking pneumatic system (PSE) located under the rear seat, and the close assist has its own pneumatic unit located in the upper left corner of the trunk behind the rear seat.

The problem you describe is quite well known.

When activating the closing system (by closing a door), the pump will run until it reaches a certain pressure or it times out (because it does not reach that pressure).

If it times out three consequetive times for a door (or trunk lid), the unit will switch off the function for that door, until the unit is reset by taking out the fuse for it (right side of trunk).

There is two main reasons, why it may not reach the pressure. Either there is a leak in pneumatic system for that particular door, or it is because the unit is not able to provide the required pressure.

Since the system switches off the function door by door, the problem is most likely in the pump unit.

This is normal when the pump gets worn. The dealer would replace the unit (VERY expensive), but there is a workaround:

Inside the unit the threshold, at which the pump will switch off when reaching the required pressure, can be adjusted. Setting it to the actual pressure, which is reached after 3-4 seconds of running, will most probably bring it back to life and extend the life for years. I have had i running for more than one year that way.

The topic is described in depth in postin #27 in the knowledge base thread (thanks Brett):

http://www.benzworld.org/forums/w140-s-class/1203330-knowlege-base-3.html
 
#3 ·
Minnet said:
First of all, the headligth range adjustment and the close assist operate via two entirely (almost) separate pneumatic systems.

The heigth adjusment operates via manifold vacuum assisted by the central locking pneumatic system (PSE) located under the rear seat, and the close assist has its own pneumatic unit located in the upper left corner of the trunk behind the rear seat.

The problem you describe is quite well known.

When activating the closing system (by closing a door), the pump will run until it reaches a certain pressure or it times out (because it does not reach that pressure).

If it times out three consequetive times for a door (or trunk lid), the unit will switch off the function for that door, until the unit is reset by taking out the fuse for it (right side of trunk).

There is two main reasons, why it may not reach the pressure. Either there is a leak in pneumatic system for that particular door, or it is because the unit is not able to provide the required pressure.

Since the system switches off the function door by door, the problem is most likely in the pump unit.

This is normal when the pump gets worn. The dealer would replace the unit (VERY expensive), but there is a workaround:

Inside the unit the threshold, at which the pump will switch off when reaching the required pressure, can be adjusted. Setting it to the actual pressure, which is reached after 3-4 seconds of running, will most probably bring it back to life and extend the life for years. I have had i running for more than one year that way.

The topic is described in depth in postin #27 in the knowledge base thread (thanks Brett):

http://www.benzworld.org/forums/w140-s-class/1203330-knowlege-base-3.html
THANKS MINNET,
I HAVE BEEN THROUGH YOUR DETAILED REPLY AND THE THREAD #27 WHICH WAS VERY EXPERTISING ON THE ISSUE WITH ALL THE POSSIBILITIES INCLUDED.
NOW SINCE I HAVE ENCOUNTERED THE PROBLEM WITH ALL THE DOORS AND THE TRUNK AFTER A SHORT WHILE FROM THE THE DRIVER'S DOOR ON ,AND RESETTING THE FUSE IN THE TRUNK SOLVED THE PROBLEM ONLY FOR A WHILE THEN SAME THING HAPPENED ,I UNDERSTAND THAT MY PUMP IS GETTING BAD OR WORN OUT AND ONLY ADJUSTING THE SYSTEM PRESSURE AS SHOWN WITH THAT SCREW DISPLACEMENT, SHOULD SOLVE THE PROBLEM.
IF I HAD A LEAK SOME WHERE I WOULD NEVER HAVE BEEN ABLE TO REGAIN THE FULL FUNCTION BY RESETTING THE FUSE ,RIGHT?
 
#4 · (Edited)
OMER PASA said:
THANKS MINNET,
I HAVE BEEN THROUGH YOUR DETAILED REPLY AND THE THREAD #27 WHICH WAS VERY EXPERTISING ON THE ISSUE WITH ALL THE POSSIBILITIES INCLUDED.
NOW SINCE I HAVE ENCOUNTERED THE PROBLEM WITH ALL THE DOORS AND THE TRUNK AFTER A SHORT WHILE FROM THE THE DRIVER'S DOOR ON ,AND RESETTING THE FUSE IN THE TRUNK SOLVED THE PROBLEM ONLY FOR A WHILE THEN SAME THING HAPPENED ,I UNDERSTAND THAT MY PUMP IS GETTING BAD OR WORN OUT AND ONLY ADJUSTING THE SYSTEM PRESSURE AS SHOWN WITH THAT SCREW DISPLACEMENT, SHOULD SOLVE THE PROBLEM.
IF I HAD A LEAK SOME WHERE I WOULD NEVER HAVE BEEN ABLE TO REGAIN THE FULL FUNCTION BY RESETTING THE FUSE ,RIGHT?
There is a separate pneumatic line from the pump assy to each door/trunk. So if there is a leak, it would only be detected when applying pressure for that particular door, and the unit would only switch the function for that door off, leaving the remaining doors functioning.

What happens in your case, is that the pump detects that it cannot reach the required pressure for any of the doors and "thinks" there is a leak for each door one by one as you use them. After 3 consequetive times failure for a door, the function for it will be shut down, and whenever you reset the unit, it will start all over letting it pass 3 times per door.

Now, back to the problem. There is a pump, that can provide a certain pressure to the doors, and there is a sensor, that will detect the pressure as it builds up. The sensor is normally adjusted to swithch off the pump somewhat below the specified maximum pressure the pump can deliver.

If the pump can't provide as much pressure as it used to, it will never reach the level, which the sensor is adjusted for. This of course happens gradually, so in the beginning it will only fail sometimes, later all the time.

Now, the pump may still provide more than sufficient pressure to close the doors, and therefor you can adjust the sensor to switch off the pump at a slightly lower pressure, so the system will be fully operational again.

Of course, you shall bear in mind, that the cause i still a pump, that cannot provide the specified pressure any more for one or another reason (in most cases wear). But who cares, as long as the closing assist works without problems.

/Jens
 
#5 ·
same issue

my car is in the shop currently ... they replaced the pump twice ... now they are looking for the leak ( the problem was with my trunk) is there a direct line to the truck? Since it seems not to be the pump will the line leading to the truck effect other areas of the car?


Minnet said:
First of all, the headligth range adjustment and the close assist operate via two entirely (almost) separate pneumatic systems.

The heigth adjusment operates via manifold vacuum assisted by the central locking pneumatic system (PSE) located under the rear seat, and the close assist has its own pneumatic unit located in the upper left corner of the trunk behind the rear seat.

The problem you describe is quite well known.

When activating the closing system (by closing a door), the pump will run until it reaches a certain pressure or it times out (because it does not reach that pressure).

If it times out three consequetive times for a door (or trunk lid), the unit will switch off the function for that door, until the unit is reset by taking out the fuse for it (right side of trunk).

There is two main reasons, why it may not reach the pressure. Either there is a leak in pneumatic system for that particular door, or it is because the unit is not able to provide the required pressure.

Since the system switches off the function door by door, the problem is most likely in the pump unit.

This is normal when the pump gets worn. The dealer would replace the unit (VERY expensive), but there is a workaround:

Inside the unit the threshold, at which the pump will switch off when reaching the required pressure, can be adjusted. Setting it to the actual pressure, which is reached after 3-4 seconds of running, will most probably bring it back to life and extend the life for years. I have had i running for more than one year that way.

The topic is described in depth in postin #27 in the knowledge base thread (thanks Brett):

http://www.benzworld.org/forums/w140-s-class/1203330-knowlege-base-3.html
 
#6 ·
Minnet said:
First of all, the headligth range adjustment and the close assist operate via two entirely (almost) separate pneumatic systems.

The heigth adjusment operates via manifold vacuum assisted by the central locking pneumatic system (PSE) located under the rear seat, and the close assist has its own pneumatic unit located in the upper left corner of the trunk behind the rear seat.

The problem you describe is quite well known.

When activating the closing system (by closing a door), the pump will run until it reaches a certain pressure or it times out (because it does not reach that pressure).

If it times out three consequetive times for a door (or trunk lid), the unit will switch off the function for that door, until the unit is reset by taking out the fuse for it (right side of trunk).

There is two main reasons, why it may not reach the pressure. Either there is a leak in pneumatic system for that particular door, or it is because the unit is not able to provide the required pressure.

Since the system switches off the function door by door, the problem is most likely in the pump unit.

This is normal when the pump gets worn. The dealer would replace the unit (VERY expensive), but there is a workaround:

Inside the unit the threshold, at which the pump will switch off when reaching the required pressure, can be adjusted. Setting it to the actual pressure, which is reached after 3-4 seconds of running, will most probably bring it back to life and extend the life for years. I have had i running for more than one year that way.

The topic is described in depth in postin #27 in the knowledge base thread (thanks Brett):

http://www.benzworld.org/forums/w140-s-class/1203330-knowlege-base-3.html
My system has worked 100% of the time for 2 years now after adjustment of the shut-off pressure.

Brett
 
#7 ·
bulldog13 said:
my car is in the shop currently ... they replaced the pump twice ... now they are looking for the leak ( the problem was with my trunk) is there a direct line to the truck? Since it seems not to be the pump will the line leading to the truck effect other areas of the car?
Replacing parts before doing any diagnostics... typical money-making approach.

Yes, there is a separate line to each door and the trunk. You can read my write-up on the closing assist system here:

http://v12uberalles.com/Closing_Assist_Pump.htm

Brett
 
#8 ·
bulldog13 said:
my car is in the shop currently ... they replaced the pump twice ... now they are looking for the leak ( the problem was with my trunk) is there a direct line to the truck? Since it seems not to be the pump will the line leading to the truck effect other areas of the car?
No, has its own circuit and should not cause shutting down the function of the doors.

Does anyone have other experience?
 
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