S500 ( W140 chasis ) trunk opening Gremlins
 

I have a 1994 S500 (W140 series chasis). When I put the car in reverse not only do the fender finder antena's come up, but also the trunk partially unlocks and the lifting handle on the trunk pops out. The trunk edge is then about 1/4 above the body metal instead of flush as it usually is. The trunk does not open all the way and seems to still be latched down.

When parked the remote trunk lock works fine, and when you press the button on the trunk to open the trunk, the lid pops up an inch or so and the trunk lifting handle pops out as it should.

When you close the trunk lightly the closing mechanism grabs the trunk lid and gently closes it fully as well as retracting the lifting handle at the same time.

In other words everything appears to work properly EXCEPT that when I place the car in reverse, some gremlin in the trunk opens the lid.

You have a problem with the central locking pump! This pump has 5 jobs that it does & sounds like it is getting mixed-up on just what to do.

Thanks for the tip. Where is the pump located and why would it be activated by simply backing up the vehicle? Does it also operate the rear corner finder antenna's?

Can anyone tell me where the pump is located.

A37, closing assist pump
 

The closing assist pump is under the back seat according to the CDROM. Never had to 'fix' mine (yet! :) ).

To remove the seats, push back the 'handles' to release from the clip. Should be on the left side.

Do you have a CD for the W140. If so where can I get one?

it's gone!!
 

On my MB web page (Menu #1; toward bottom of the page), I have a link to get the Alldata (AutoZone) CDROM

However, after checking it today, I find it's gone! And replaced by a $24.95/yr subcription. Wow!

Here's link as it looks today: http://www.alldata.com/products/index.html There's an Alldata DVD available but no price mentioned. I'll bet it's steep! :confused:

Gremlins
 

Jere;
The control unit you seek is acessed from the trunk,it is in the front upper left side of the trunk.
Pull down the covering and look for a foam enclosure ,the unit is inside.
Don't fool around--- replace it !
M.F.

The central locking is under the rear seat inside of the car!! THE closing assist pump is IN the trunk, just on the left of the fuel tank.

YOU are having a problem with the CENTRAL locking system, try under the rear seat on the right side of the car!!

Donnie:
I think that this depends on the year and if has a modification done or not. The first few years, the 140 used the CA pump for pull-down, then they changed their mind and if the system needed repair a modification was required which switched it to the PSE. Ring a bell??
Gilly
ps I think I'm on the right track since his is old enough to have the rods on the rear 1/4 panel.

Pulling down of the trunk has always been closing assist!!
The trunk handle & back-up antenna's have always been central locking(PSE pump).
Check the original complaint, trunk handle & back-up antenna are the problems.
Only 1992 & early 1993 cars were modified as far as closing assist signal switch.
There is a vacuum element that is controlled by central locking pump operation that is on the trunk lock, look at the vacuum circuit & complaint!

Body and Accesories chapter 3.1 PSE/RTG, page 32/1:
NOTE:
As of 12/93, in vehicles as of chassis end number 118 121, pressure or vacuum for the lock stiker actuator is applied in parallel with the retractable trunk lid grip actuator.
++++++++++++++++++++++++++++++++++++++++++++++
BT80.40-P-0001-01A "Power locking with additional quick release"
Model 140.#### ## as of 118121
Function: para. 2
"If the trunk lid is opened the PSE applies pressure to the retractable trunk lid handle (RTH) as well as the striker eye for power locking via an additional element (2) causing them to extend.
++++++++++++++++++++++++++++++++++++++++++++++
I also think there is a modification that has to be done if the striker actuator goes bad, I couldn't find it, I believe there is an SI out there concerning this, that you change the vacuum/pressure source from the CA (which up until number 118121 would have been providing the vac/pressure) over to the RTG lines, which came from the PSE.
Since he is complaining of both the RTG and the striker extending, I would tend to agree that his is either post-118121, or has been modified due to replacement parts, since only these 2 scenarios would act in this way, unless he has a way-too-coincidental failure. And since the back-up assist rods are PSE actuated also, it really does sound like a bad PSE.
My only point is that only the first 118,121 cars had the power striker operated by the CA pump, after that it operated on the same line from the PSE as the RTG. (for those not familiar with these, the RTH (retractable trunk handle) is often referred to as the RTG (retractable trunk grip), same part, different acronym.
Gilly

Dan, I have a 140 series 1995 S-350 and the trunk handle sometimes goes back out after the trunk is closed and it is sucked in. Just pops back out. The trunk does not open but the lights inside the trunk come on and the dash light lights up as to the trunk being open. I have adjusted the mechanism and it seemed to help a little. It might work properly for a week then all of a sudden pop back out. Very agrivating. I have tried oiling it with only marginal success. I even got into the trunk an had my daughter shut the lid where I could see what was going on. It appears there is a microswitch that a little rotating lever goes against. The lever is not rotating far enough when it malfunctions. Any ideas or does the whole thing need to be replaced?

It would be interesting to see if the anti-theft alarm will work when this happens. Ultimately it sounds like it needs a new trunk latch assembly, I believe this is seperate from the lock cylinder. If the rotary part of the latch isn't turning far enough, it sounds like the latch itself is at fault. The vacuum element is only for locking and unlocking, shouldn't affect the rotary part. Maybe Donnie has an idea.
I will try to look up and see if I can get a more positive answer.
Gilly

By the anti theft alarm do you mean will it go off and blow the horn. If so I have not tried that yet, but the infared remote still locks and unlocks the trunk properly. Everything is right except the handle is out and the trunk lights are on as is the dash light. If I just close the trunk and go in the house without waiting to see if the handle comes back out, the next day my battery is weak from running the trunk lights all night long.

SO Dan (gillybenztech) you are saying the PSE pump is responsible for the problems that JERE is having with his back-up antennas & trunk handle!!! Just as I posted to begin with!!
The mod that had to done on earlier cars was already on this car, ie; S500 means 1994 & later.
ALSO the inside trunk release is done by running the PSE central locking pump, customer says that the trunk opens when putting car in reverse!!
ALL of this leads to problem with PSE(central locking pump) problems.
CLOSING assist ONLY pulls the trunk & doors shut!! Nothing else.

Old South

According to my tech at the MB dealer there was a modification made in 1995 to the trunk latching system...so your car may be a different animal than the problem vehicle
I myself had problems with the latching mechanism(tongue) a couple of years ago...it worked for a while to pull out the fuse9in the trunk) to reset the pump.But finally the closing assist pump was replaced.
The door closing assist always worked well though


Warren
1992 300SD(140)
Columbus Ohio

I have already replaced the closing assist pump in the trunk about a year ago when the doors stopped closing themselves. I hope it is not going out again to cause the trunk problem. I don't think it is the pump because I can mess with the latch when the problem surfaces and that usually solves it for a while.

Donnie:
Either Dan or Gilly is fine.
I left out one important note 2 posts ago where I was quoting stuff:
In Body and Accesories Chapter 6.1, which is the Closing Assist chapter, they have a test for the trunk pull-down also, it's test step 15, on page 33/9. This indicated that the early cars did use CA for trunk pull-down. They also have that same note about the "starting with 118121" it's pulled down by the PSE in parallel with the RTG.
I'm not trying to be confrontational about this. Yes, I do believe the problem is the PSE for several reasons. #1, if it were old enough to be the CA pulling down the trunk latch tongue (pre-118121), it makes no sense why it would do it in reverse, since the PSE is in charge of the reverse rods. Also "Jere" hasn't replied to posts here for awhile, but since he stated the car is an S500, it probably is a newer car, as cars this old (pre-118121) would probably be badged a 500SEL yet.
On Warrens car, I believe that a replacement of the PSE would have repaired a problem with the trunk pull-down, as we have been discussing. Maybe someone referred to it as the closing assist pump, but i think they meant PSE pump, may have used a term more understandable than "PSE". The PSE pump is more understandable if described as the "central locking" pump. As it is, I think PSE can be loosely translated as "Pneumatically Slaved Equipment".
On Old South's car, the more I think about it, the more I think it has to be the latch itself. Possibly the microswitch, but since you observed the cam not properly contacting the switch, make more sense it is a latch problem. You should be able to monitor this just by closing the latch with your finger or a screwdriver.
If it happens quite often, it would be easy to diagnose by simply monitoring the "actual value" screen on an MB tester (HHT or SDS) in the PSE control module.
Gilly

so you think a replacement of the PSE would have repaired my car?..is this any less expensive to replace than the closing assist pump?

curiously after the replacement of the closing assist pump I have had no other problems...well with that issue anyway!!!

a friend in town who has a 1992 400SE had the same problem except his doors would also fail intermittently.....same fix...they replaced his closing assit pump also

except for my engine problem he and I are running neck and neck on repairs...both of us have had almost identical work done with the exception of power steering pump and rear end problems that I have not had.....but he has not needed an evap core replacement either

No, what I am suggesting is that the replacement of the PSE DID repair your car since the PSE on a 95 controls the action of the striker tongue. Please reread my previous post. The CA pump only controlled the striker tongue up until VIN 118121. Your friends 92 is probably pre-118121 and may very well have needed a CA pump to repair his car.
I am unaware of the cost difference between the CA and the PSE.
Yes there is a modified striker tongue for the post-118121 cars, it is the only one available for these cars. It is faster acting, they had complaints I guess on how slowly the lid closed.
Gilly

the cost of the replacement of the closing assist pump on my car was about $800.00 parts and labor at the MB dealer.The cost was covered by warranty....curiously I was also having occassional problems with my reversing rods not retracting...but all the tech did was to clean the switches that activate them and that seemed to clean up the problem ... that was two years ago and I have not had any more issues with the reversing rods

he did however tell me at the time that I could have the updated latch(that was less probelmatic) from the 1995+ cars installed...however if I chose that I would have to pay $300.00 from my own pocket..I declined
The new pump seems to be faster acting than the old one...also seems to be stronger as I accidently closed the driver's door on a half inch piece of plastic the other day and door closing device snapped the pice in two.....made me wonder what would happen if a child got his hand closed in the door accidently...there is definitely enough force they to break a finger


Warren
1992 300SD
Columbus Ohio

Bosch recall
 

Donnie, didn't you mention that Bosch had a recall on the close assist pumps? What ever became of that and how can I tell if I am purchasing a good one? On my 92 500 SEL I have to slam the drivers' door and trunk shut. The trunk stopped pulling down the lid and the chrome handle does not come out any more either. The drivers door is the only one that will not close automatically. The trunk may be a combination of the other pump you mentioned that is located under the rear seat. I say this because I have had the lights in the trunk to go out again after replacing the fuse in the rear trunk conpartment. This would lead me to believe that the pump under the seat may have problems. I am going to disconnect it and replace the fuse as mentioned before to see if the pump is drawing too much.

Thank You

Fred Berry
frederickberry@peoplepc.com