MB-Dude

Been battling this problem for a while now - When using the automatic trunk closing activation, the lid travels down fairly quickly but does not stop until it slams into the latch and is physically stopped by the body frame. Because the lid travels 'too far', the normal soft-close function never gets a chance to activate. The soft-close function works correctly with the lid open and I can use a screwdriver to simulate the latch engagement. This is not an intermittent problem; it occurs every time. If I close the trunk lid by hand, the soft-close grabs the latch at the correct time and pulls the lid slowly closed. I have changed the PSE; same result, no change. Using Star, I normalized the trunk lid - no change.

Looking for any information on how the trunk lid 'knows' when to stop. If it were not for the physical body frame, the lid mechanism wants to continue travelling downward. In fact, the little trunk hydraulic pump keeps running for a couple seconds after the lid has completely slammed into place. This suggests that whatever tells the PSE to turn off the pump is not doing so. Any insight, especially from the MB Technicians, would be fabulous. Thanks in advance.

Cheers,
Jeff

Fried Chicken

Do you suspect a leak in the air line causing the system to be physically unable to stop the trunk closing?

MB-Dude

Hmmm... Please elaborate. I'm unaware of an air line associated with trunk closing, so I may be learning something new here. Thanks.
Cheers,
Jeff

Russell Ormerod

Hi there. There is no sensing mechanism as far as I am aware. Unlike the ML which has an angle sensor. Your problem Is most likely mechanical. Check the dampening struts that are fitted near the hinges they are extremely hard to compress. If one has collapsed or has lost it dampening action the boot will slam. And possibly also not stay up at times. Good luck

MB-Dude

Thanks Russell for the thoughts on the struts. Both have been replaced within the last 3 months with MB-dealer parts. They were replaced to solve a lid-won't-stay-up problem. But the trunk slamming was occurring before I replaced them.
Cheers,
Jeff

Russell Ormerod

Hmm. Strange one. I will have a look into it. Let me know what u find

MB-Dude

It's as if the lid closing pump is activating for too long a time, or whatever mechanism/signal/timeout/whatever that is supposed to turn off the pump is not being triggered correctly.
Cheers,
Jeff

Fried Chicken

I was thinking of the struts, sorry, I really don't know how the self-closing trunk works.

ibeforreal

Jeff, I have a similar problem. The struts have been replaced and the trunk stays up. However, just as yours when I hit the trunk close button it seems to come down normally and then just before it gets to the point where it meets the latch it speeds up. It certainly has me and my buddie who is a specialist scratching our heads. If I find anything out I'll let you know.

doni01

iTrader: (1)

Mine does the same exact thing but I have problems with soft close so I have been blaming it on that. Just got a pump from a different car and gonna swap it with mine. See what happens...

Russell Ormerod

Guys next time I get a s class in the shop I will check the boot function

MB-Dude

John - You probably have the same situation as I do. The lid appears to move faster as it approaches the latch, but I think it's just the geometry of the drive cylinder and the trunk hinge.

Doni - Yes, looking forward to seeing if the pump swap helps. Soft-close issues are very obvious. Usually the trunk stops on the latch, but is not pulled down.

Russell - Thanks. This problem is a real bugger, mainly because I can't find any information on what causes the trunk lid hydraulic pump to stop. I'm not sure what to check, other than shots-in-the-dark.

Cheers,
Jeff

JoeNobody

Is there a control module for the trunk closer? My W211 E55 was slamming the trunk lid and almost took your hand off. Turns out, as the trunk closer control module gets older, it slowly keeps getting faster and faster in slamming the lid. Replacing the module with an updated design, and the problem was fixed.

MB-Dude

Thanks for the input Joe. To my knowledge, the PSE module receives input data from the trunk lid positional sensor and the latch assembly within the trunk lid. The PSE then sends activation signals to the trunk lid hydraulic pump. In theory, changing the PSE should resolve the issue. Problem is, I have changed the PSE module and it had zero effect on the situation. Also, Xentry/DAS suggests the correct parameters are being read by the PSE. To solve this problem, we need to know what triggers the pump to stop. Working back from that point will lead us to the failure.
Cheers,
Jeff

doni01

iTrader: (1)

Jeff,
I finally got around to swapping the pse pump. The problem still happens and it is exactly as you described it. If I lower it manually, it will allow the soft close to kick in and do what it is supposed to but if I press the red button to close it, it will slam down and not give the soft close a chance to work. I also replaced the shocks on the lid with new ones from the dealer since my lid wasn't staying open but it still does it.

MB-Dude

-BUMP- Keeping this frustrating issue alive. Any additional input? Really hoping an MB Tech can chime in on how the trunk closing sequence works, specifically what triggers the trunk lid hydraulic pump to stop. That's the key to this problem - the pump is not being told to stop and keeps running, forcing the trunk lid to slam shut.
Cheers,
Jeff

doni01

iTrader: (1)

I agree !! I was thinking it is somewhat a common problem since there is a few of us having it. Funny thing is that I went to my independent shop that only deals with German cars and they said on how they haven't seen it

Russell Ormerod

Have not had a car in to test. But honestly don't think anything tells the pump to stop

MB-Dude

Something has to turn the hydraulic pump off. It is supposed to stop just short of fully engaging the latch so that the soft close can gently pull the lid down. In my case (and I think others), the pump never turns off, which causes the lid the slam shut. Soft-close never gets a chance to activate. And my pump keeps running for a few seconds after the lid has latched. Something is supposed to turn the pump off to allow soft-close to complete the last lid movement to fully latch.
Cheers,
Jeff

tusabes

My Lid slams shut too

ibeforreal

I'm still watching and waiting for a possible answer.

doni01

iTrader: (1)

Maybe that's what it is supposed to do ?? Any other owners wanna chime in ??

tusabes

Ask in the cl and s class amg forums more people respond there

kraut56

I went thru this a few years ago after I bought the car; my problem was that the car would not "go to sleep", and continue to draw about 800 - 1200 mA.

Took me a year to get it to work right (almost), with some help from Eric in China.

The hinge geometry is mental, and appears to wear easily.
The hydraulic pack brings the lid down, and there is a proximity sensor behind the actuator to know where the lid is (both opening and closing).

On the closing cycle a timing circuit is activated, that monitors how long between hydraulic closing and locking by the soft close (must be less than 10 seconds, otherwise you get a fault in DAS to that effect ..."time exceeded..).

The pump still runs while the soft close engages (!).

The lid stops must be adjusted such that the lid can "overtravel", so when the soft close releases, the lid goes up by a few millimeters.

If you search my posts here and on Benzworld you will find my posts on the trunk hydraulics and the lid adjustment.

Good Luck!

Russell Ormerod

I had a chance to check this closing system. There is no proximity sensor but there is angle sensor measuring lid position. There is a learning process on star. Also in actual values you will be able to see the full open position and also full closed position that the sensor reports to PSE. Also the boot catch sw must be functional for learning to be done. And of course mechanical gas struts in good working order. Guys have a look at actual values of boot position and report back