Pneumatic System Not Working??
Thread Starter
Newbie
Joined: Mar 2005
Posts: 2
Likes: 0
Pneumatic System Not Working??
Been searching the forum and cant find the answer...
Today when getting into the car at the mall, noticed that I had somehow left the doors unlocked.... found that the locks, trunk and assisted doors werent working as well as the corner markers on the back(whatever those are called).
This has always worked flawlessly up until today.... Of course I had a buyer looking to buy the car today.
Anyways, I believe this is an air leak as I do hear a hissing sound near the right rear wheel.
I have tried removing the fuses and re-inserting. But that didnt work.
Any Ideas? 1992 SE500.
-Thanks!!
Today when getting into the car at the mall, noticed that I had somehow left the doors unlocked.... found that the locks, trunk and assisted doors werent working as well as the corner markers on the back(whatever those are called).
This has always worked flawlessly up until today.... Of course I had a buyer looking to buy the car today.
Anyways, I believe this is an air leak as I do hear a hissing sound near the right rear wheel.
I have tried removing the fuses and re-inserting. But that didnt work.
Any Ideas? 1992 SE500.
-Thanks!!
MBWorld Fanatic!
Joined: Apr 2006
Posts: 2,290
Likes: 1
From: New Zealand
1993 300SEL/S320
The hissing sound is the fuel pump, thats normal. Your PSE or central locking pump has broken. It's located under the back seat and they quite often go. You'll most likely find that the lumber support is nolonger working on the front seats either.
Senior Member
Joined: Jul 2003
Posts: 455
Likes: 1
From: Fl
92 500sel/01 320e wag
There are two pumps on the car, the one under the passenger rear seat is the lock unlock pump for doors fuel and trunk.. The other is the "close assist", which controls doors,trunk lid, lumbar, backup rod, and HVAC vacuum when engine is off, that one is located over the drivers side rear wheel next to the fuel tank.Check this out:
http://v12uberalles.com/Closing_Assist_Pump.htm
http://v12uberalles.com/Closing_Assist_Pump.htm
Last edited by Peter Guenther; Aug 1, 2008 at 08:17 AM.
Junior Member
Joined: Dec 2005
Posts: 70
Likes: 1
From: Houston, TX
02 S55
Peter, I'm surprised at you - you've got your "what does what" wires crossed.
The Close Assist Pump does only that duty: pull the doors shut, and pull the trunk shut. It is a vacuum-only (I think) pump.
The PSE pump, located under the right-rear seat cushion handles all other functions on the car.
It is a vacuum or pressure pump depending on the job to be done.
Pressure to: inflate lumbars, extend backup guide rods, extend trunk handle, unlock doors, unlock fuel door and assist with extending the locking pawl on the trunk lid.
Vacuum to: retract backup guide rods, retract trunk handle, release the rear headrests on cars so-equipped, lock doors, lock fuel door and help with vacuum for the HVAC.
However, if the OP is having trouble with the door closers, and the doors aren't locking, then there's something amiss with both systems.
We all know that the closing assist will permanently disable the assist any door (or the trunk lid) when that opening doesn't latch closed within a certain number of seconds over a certain number of attempts. R&R'ing the fuses for the close assist pump resets those lockouts. However, it's a rare thing for all of the doors to get locked out at once.
The doors not locking and the reversing masts not extending are certainly a symptom of a failed or failing PSE pump. As you noted, nobody's tried to home-repair these devices, they're wickedly complicated compared to the close assist pump. I'm pretty sure the PSE pump has a similar lockout feature as the close assist pump, but I think the lockout isn't permanent, it resets each time the car is restarted.
As for the question from Noel about the lines, the design and routing of the lines makes for a very reliable system in that regard. Failure of multiple systems usually points to the pump itself.
The Close Assist Pump does only that duty: pull the doors shut, and pull the trunk shut. It is a vacuum-only (I think) pump.
The PSE pump, located under the right-rear seat cushion handles all other functions on the car.
It is a vacuum or pressure pump depending on the job to be done.
Pressure to: inflate lumbars, extend backup guide rods, extend trunk handle, unlock doors, unlock fuel door and assist with extending the locking pawl on the trunk lid.
Vacuum to: retract backup guide rods, retract trunk handle, release the rear headrests on cars so-equipped, lock doors, lock fuel door and help with vacuum for the HVAC.
However, if the OP is having trouble with the door closers, and the doors aren't locking, then there's something amiss with both systems.
We all know that the closing assist will permanently disable the assist any door (or the trunk lid) when that opening doesn't latch closed within a certain number of seconds over a certain number of attempts. R&R'ing the fuses for the close assist pump resets those lockouts. However, it's a rare thing for all of the doors to get locked out at once.
The doors not locking and the reversing masts not extending are certainly a symptom of a failed or failing PSE pump. As you noted, nobody's tried to home-repair these devices, they're wickedly complicated compared to the close assist pump. I'm pretty sure the PSE pump has a similar lockout feature as the close assist pump, but I think the lockout isn't permanent, it resets each time the car is restarted.
As for the question from Noel about the lines, the design and routing of the lines makes for a very reliable system in that regard. Failure of multiple systems usually points to the pump itself.
Senior Member
Joined: Jul 2003
Posts: 455
Likes: 1
From: Fl
92 500sel/01 320e wag
Wow
Yes I did get my wires crossed, the close assist does exactly that, sends pressure to the elements to draw in the doors and trunk, and then vacuum to purge the system and reset the diaphrams. The lock/unlock does do all the other things, like lumbar, back up rods, and things. After reading my response thanks for correcting me!
