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Discussion Starter · #1 ·
Hey! Does anybody have any suggestions for service and/or repairs on the back-up assist pins in W140-LWB models? (they don't go up/down anymore and is stuck in a mid position)I've checked all the fuse boxes already, so it's probably the relays, it also took out my power locks & trunk handle!(it doesn't pop out or eject anymore when you open the trunk) Any comments, suggestions, or home remedies would be greatly appreciated!!! (My Dealer Told me it's $75.00 to diagnose the problem and perhaps a $700.00 repair) [:0]
 

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92 500SEL to 01 E320T current 2014 lexus LS460
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Back up sssist

The door locks(lock and unlock, backup assist, and some other functions are controlled by a vacum pump under the rear seat. The pump could be bad, but the good news might be a article in this months "STAR" magazine. It seems there is a hose in the pump itself that goes bad causing the pump to not do its thing. The bulletin suggests opening and replacing the hose Part# Q4 80 0001, it might be the fix, if not the pump is a pricier option. Take up the rear seat it is in foam rubber holder on passenger side, and operate the system to see if you can hear it run. You can go from there!
 

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W140 S class, E31 850Ci, XC90 Exec AWD geartronic
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444 Posts
Vacuum pump

Over the last few days, my 94 W140 has developed the symptoms.

(1) Central locking failure
(2) Parking Aides down
(3) Boot handle stuck in the 'out' position

Like Trent S320, I've checked the obvious like fuses and nothing seems to be wrong. The vacuum pump under the back seat doesnt make any noise. Where do I start? Should I open the pump up?
 

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300 SE
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27 Posts
Door locks and assist

quote:
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My 1992 S320 has vacuum door but it doesnt work, Ive tracked a leak down to the lumber bags which Ive fitted new ones (£26 each). Does any one know where the resiviour is, as I need to trace the air line back to its sourse. Im sure the other end has come off as well. Does any one have a manual for this car?

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I have a 92 300 SE which has the vaccum assist which I just replaced the pump on. It is in the trunk on the left side next to the gas tank. It is very easy to replace. It's cost is about $198.00 US currency rebuilt from George Murphy (email address) [email protected] the door locks and truck handle pump is located under the rear seat on the right side of the car. This one costs about$400.00 US currency from George and is new. Good luck with these issues. I fixed both of mine this past weekend and glad that I did. The door locks and lumbar are on the same pump. Door and truck closers are on the other pump.
 

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92 500SEL to 01 E320T current 2014 lexus LS460
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S Class locking

One more time.
There are two pumps, one to lock and unlock the doors the pump is under the rear seat, it does more than that, lumbar, trunk handle,some headrests and park assists. The other near the fueltank over the rear wheels closes the doors and trunk lid. There have been some bulletins namely in the last "STAR" WHERE THEY ADMIT A PROBLEM WITH THE CLOSING PART. The other is still a issue for $500-600 and no fix other than purchasing a new assembly, almost all 140 s have the issue. There are lawsuits over oil changes, why not these pums and AC issues
 

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W140

I had the same problem with my 600sel and the lumbar support was not working as well as the auto closing doors. I left the car for over a month (while on vacation) and the batteries ran out. after re charging the battery and typing the 4 digit code into the radio everything started working again. i think by disconnecting the batteries it re set the computer.
It may be worth a try. -hope this helps -kristian
 

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92 500SEL to 01 E320T current 2014 lexus LS460
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Pulling the (2) fuses and waiting ten seconds or so, sometimes helps if only one or two de...

Pulling the (2) fuses and waiting ten seconds or so, sometimes helps if only one or two devices dont pull in. It usually lasts for a short time, the ultimate replacement is just that!
 

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W140 S class, E31 850Ci, XC90 Exec AWD geartronic
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Can you tell me which fuses to pull? I know the location of two fuse boxes, One in the t...

Can you tell me which fuses to pull? I know the location of two fuse boxes, One in the the engine bay by the windshield and the other in the trunk behind the fuel filler down pipe

Thanks
 

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Discussion Starter · #11 ·
No Pete, I didn't. Are you suggesting pulling out all the No.2 fuses in the trunk might ...

No Pete, I didn't. Are you suggesting pulling out all the No.2 fuses in the trunk might help? I haven't done it yet, but I'll try. (the damn pumps are too expensive)!!![|)][|)][|)][|)][|)]
 

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92 500SEL to 01 E320T current 2014 lexus LS460
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Locking pump

I had the closing assist in the trunk go twice, I screamed and they replaced it under "cusomer satisfaction" The fuses in the trunk usually have to do with the "closing assist" doors and trunk. The pump under the seat is for locking, the back up assist, headrests in some, vacum assist for the heat/ac, and i think the seat bolsters. I dont know where the fuse is (knock on wood)and hope I dont have to search for it. The pump uns untill it sees vacum or pressue build up, which would indicate all the diaphrams are pulled in or out. If it does not see this condition in some (10sec or so)it shuts off assuming there is a leak. This where the issue of a defective hose comes from and a bulletin from MB to open the pump and replace. I guess if the motor does not run there is another issue. It is in a foam rubber container and pretty quiet lift up your rear seat and investigate
 

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W140 S class, E31 850Ci, XC90 Exec AWD geartronic
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Here is the story so far......

About 3 months ago I noticed later that the lumbar support didn’t feel right and my seats felt saggy, I tried to adjust my support and the system didn’t respond. This was also the case with the front passenger seat.
In the winter (about two months ago) in exceptionally cold snowy weather, the central locking system died in my car.
I could unlock the doors individually with a key.
I assumed it was likely a fuse had blown and didn’t think too much of it.
Later that day I opened my trunk and the handled (very slowly) popped out and didn’t return when closing the lid. On further investigation I noticed that my parking aides no longer popped up when reversing and my headrest down function didn’t work.

I disconnected the battery for about 10 minutes and tried again. The locks started working for about 10 seconds and then died again. I could still hear the relays clicking beneath the rear bench, but no action.

I lifted the back seat to access the pump unit. All hoses/connections appeared fine and intact.
I carefully, labeled all the hoses and then disconnected them one at a time.

I started the car and connected the live hissing hose by hand to each of the lines. All devices operated with connection and I was able to 'down' my headrests, 'in' the trunk handle the by connecting the appropriate hoses.

This means there is no leak in the hoses and the engine is still supplying the vacuum.
The clicking of the relays also suggests that the controls are still working and current is being sent to the pump.

I removed the pump, opened it and examined the insides. There was a red coloured hose with looked worse for wear so I tried to replace it with a new vacuum hose (a small piece of windscreen washer hose) which fit snug and well. While the unit was open I examined the PCB for breaks in the solder and wiring which may have occurred due to fatigue. I also took it on myself to clean the contacts in the vacuum micro switches with spirits. I then reassembled the unit, reconnected the hoses and tried again.

No joy. I reckon the pump has had it. I am now faced with buying a new pump. Does anyone know much these units sell for? and what are the options/costs for getting a rebuilt unit/ or one from a breaker.

I don’t know of any supplier other than the main dealer.

I am open to all suggestions and help you may have to offer
 

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92 500SEL to 01 E320T current 2014 lexus LS460
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140

Here goes, you confirmed that all your devices are working, but did you ever get any noise or activity from the vacum pump? The pump supplies either vacum or pressure depending on which way the motor turns. While you have it out, and connected operate the headrests or lumbar, listen for it to whine. There was a bulletin from MB and it addressed defective (red hoses) which can be had from your dealer. but if there is no attempt to start there is a "relay" issue which causes the motor not to run. If it does run and shuts down there is a timing circuit, if it can not build up pressure or vacum. I dont recall but pricing is in the $300-400 and dont know of any other sources, purchasing from a dismantler could get you into another set of problems. There was a post from someone who went that route and got one that was not identical, there were two versions for my 92, and i would think the same applies to your year.
 

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W140 S class, E31 850Ci, XC90 Exec AWD geartronic
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thanks for the speedy response...

Hi again Peter,

When the device is activated, I can hear the relays clicking. I do not hear the familiar whine from the pump - hence it's not starting.

I dont think its the red hose, I've already tried replacing it.

As per your suggestion I'll steer clear of breakers and contact the dealer on Thursday to find out the price of the pump

By the way my car is a 1994 LWB S320 - now developed transmission problems (flaring between gears / hesistant to upshift) ...SIGH...
 

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W140 S class, E31 850Ci, XC90 Exec AWD geartronic
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Ouch...

Hi again Peter,

When the device is activated, I can hear the relays clicking. I do not hear the familiar whine from the pump - hence it's not starting.

I dont think its the red hose, I've already tried replacing it.

As per your suggestion I'll steer clear of breakers and contact the dealer on Thursday to find out the price of the pump

By the way my car is a 1994 LWB S320 - now developed transmission problems (flaring between gears / hesistant to upshift) ...SIGH...
I just called some suppliers of Merc parts, here's the responses

Eurocarparts - We dont do that part
German and Swedish - We do vacuum pumps for just about every other model for about £90+vat apart from the W140 S class
Mercedes Benz main stealer - Part has to be ordered in from germany. To supply only it will cost £412.34+vat

For those of you in the states, vat is value added tax 17.5%

OUCH!!!....I am at the end of my tether, I am going to try and fix the old one again!!! [xx(]

Mmmm...I wonder if I can buy the one for £90+vat and use common parts to re-build my own one [?]
 

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S320W
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Re: Ouch...

I just called some suppliers of Merc parts, here's the responses

Eurocarparts - We dont do that part
German and Swedish - We do vacuum pumps for just about every other model for about £90+vat apart from the W140 S class
Mercedes Benz main stealer - Part has to be ordered in from germany. To supply only it will cost £412.34+vat

For those of you in the states, vat is value added tax 17.5%

OUCH!!!....I am at the end of my tether, I am going to try and fix the old one again!!! [xx(]

Mmmm...I wonder if I can buy the one for £90+vat and use common parts to re-build my own one [?]
Whats the part number? Let me try to find a cheaper one here in the USA for you.

///S320
 

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W140 S class, E31 850Ci, XC90 Exec AWD geartronic
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can you send me the full link for germanstar.com - I get a pen retailer when I try that ...

can you send me the full link for germanstar.com - I get a pen retailer when I try that address.

Thanks [:)]
 
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