Vacuum on doors & trunk on S420
Thread Starter
Newbie
Joined: Nov 2003
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95 S420
Vacuum on doors & trunk on S420
Has anyone had problems with the vacuum on the doors and truck not working? I have changed the pump but the doors only work for a short time and then i have to reset the pump. This is done by taking out the fuse and putting it back in. This is very frustrating.
Help, Help Help.......
Help, Help Help.......
Senior Member
Joined: Jul 2003
Posts: 455
Likes: 1
From: Fl
92 500sel/01 320e wag
Door closing assist
I hope I dont offend you, but the closing assist pump is over the rear wheel, next to the gas tank, bedind the "bose amp". It requires the removal of both trunk liners, The locking pump is under the rear passenger seat.
Did you replace it with a brand new pump, or something else?
I have had two go bad, but only after a few years, and the dealer "good willed the second". They did check the lines with a vacum/pressure pump to make shure the system did not leak.
There are people on e-bay selling defective pumps (rumors). If this was a new pump, contact your parts manager. The reset proceedure you describe identify it as a bad pump. There are some rebuilts out there.
Did you replace it with a brand new pump, or something else?
I have had two go bad, but only after a few years, and the dealer "good willed the second". They did check the lines with a vacum/pressure pump to make shure the system did not leak.
There are people on e-bay selling defective pumps (rumors). If this was a new pump, contact your parts manager. The reset proceedure you describe identify it as a bad pump. There are some rebuilts out there.
Thread Starter
Newbie
Joined: Nov 2003
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95 S420
I have replaced the pump you described and the lines have been checked. My mechanic told me it might be some control unit under the hood. I'm not sure. I'm just afraid the dealer will charge 2 arms and 2 legs to find and fix the problem.
Senior Member
Joined: Jul 2003
Posts: 455
Likes: 1
From: Fl
92 500sel/01 320e wag
Closing assist
There is no "underhood computer" module involved! All the logic is in the pump. Your mechanic does NOT understand the system!
Each of the doors and trunk have a vacum diaphram attached, when the door closes to its first position it sends a signal thru a microswitch to the trunk mounted pump. the pump starts and routes vacum to the particular door. This in turn pulls in the lock untill the door closes fully, (the switch opens and shuts off the pump). If you look carefullly you will see the doors and trunk lid "pull down" and then relax. The pump does have a safety so there is not excessive vacum developed, and so it does not run longer than a specified time, in case of a vacum leak. There have been people experimating with the safety setting and getting this pump to run alittle longer, and close the door. This could be dangerous since you could damage the locks or diaphrams, resulting in excessive expenses of opening and repairing the doors etc.
This seems to be a classic case of a bad pump, where is it from? If it is brand new, why wont MB parts warranty it. My dealer suggested pulling the fuses for short term fix, but the problem occurred so often that I finally bit the bullet and had it replaced at a cost of $800 in 97, it worked perfectly untill 02, when it acted up again the same way they replaced it again under "customer good will" There is another "mod" that reroutes the handle to the closing pump from the locking pump (under rear seat).
Each of the doors and trunk have a vacum diaphram attached, when the door closes to its first position it sends a signal thru a microswitch to the trunk mounted pump. the pump starts and routes vacum to the particular door. This in turn pulls in the lock untill the door closes fully, (the switch opens and shuts off the pump). If you look carefullly you will see the doors and trunk lid "pull down" and then relax. The pump does have a safety so there is not excessive vacum developed, and so it does not run longer than a specified time, in case of a vacum leak. There have been people experimating with the safety setting and getting this pump to run alittle longer, and close the door. This could be dangerous since you could damage the locks or diaphrams, resulting in excessive expenses of opening and repairing the doors etc.
This seems to be a classic case of a bad pump, where is it from? If it is brand new, why wont MB parts warranty it. My dealer suggested pulling the fuses for short term fix, but the problem occurred so often that I finally bit the bullet and had it replaced at a cost of $800 in 97, it worked perfectly untill 02, when it acted up again the same way they replaced it again under "customer good will" There is another "mod" that reroutes the handle to the closing pump from the locking pump (under rear seat).
Thread Starter
Newbie
Joined: Nov 2003
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95 S420
I could have been mistaken by saying under the hood. What I think it is is a bad microswitch. What's happening is that once I reset it using the fuse it works for a while and then it just stops working. The pump has been replaced and my friend who has a independent shop took it to his friend at a MMZ dealer and it was determined that it was the microswitch, but the microswitch it pretty expensive from what I gather.
It's just really frustrating to keep restting the fuse all the time, Grrrr.
Rangel
It's just really frustrating to keep restting the fuse all the time, Grrrr.
Rangel
Senior Member
Joined: Jul 2003
Posts: 455
Likes: 1
From: Fl
92 500sel/01 320e wag
Closing assist
That closing pump issue is very common, altho the microswitch is not! I At one point I was thinking of installing a relay that would take the fuse out of the circuit but I could not decide what to trigger it with, and when. If you have identified one door as the culprit you are on your way, I would immagine the switch would be available, (unless you have to go the whole lock route)but getting to it has to be a real pain. You just have to slam it harder in the meantime. If it affects the trunk, and other doors randomly, it still is the pump!
Last edited by Peter Guenther; Nov 17, 2003 at 12:19 PM.
Member
Joined: May 2003
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The pump being reset by removing the fuse is the classic symptom of a bad pump. Its kind of odd since yours is new.
Try borrowing a pump from a friend or just get your pump warrantied by MB.
You guys paid $800 for your pump? I bought from Hong Kong and it only cost me about $500.
Try borrowing a pump from a friend or just get your pump warrantied by MB.
You guys paid $800 for your pump? I bought from Hong Kong and it only cost me about $500.
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Senior Member
Joined: Jul 2003
Posts: 455
Likes: 1
From: Fl
92 500sel/01 320e wag
Closing assist
Do you trust your mechanic, did he change the pump, where is the bill form (MB) so you can warranty. Who has the old one? I hope you got it back. First you state that he told you it was the computer, now its the microswitch (buddy at MB) diagnosed it. I used the dealer, it may cost a little more but it is fixed. It seems you are afraid to spend the money, but you are are in the end.
Sorry for the lecture!
Sorry for the lecture!
