On my 2003 W220 S55 AMG Kompressor the Hydraulic Trunk Closure assist system is working but fails to close the trunk lid fully either with the switch in the drivers door as well with the buttons on the trunk lid itself. I am aware that the lid is operated by a synchronised working of the EPS pump controlling the operation of the actual locking system and the soft closure feature and a hydraulic system controlling the trunk lid open & closing movement. both system signalling each other on status of the lid position.
When I pull up the door switch I have to hold it for a while before the PSE system releases the lock and then the hydraulic system opens the lid (Either completely of half way depending on the setting). When I either press the door switch or the closure button (Lighted red) on the trunk lid edge the hydraulic system starts closing the lid till it hits the lock catch but then the hydraulic pump suddenly stops not "Forcing" the lid enough down to make the lock catch engage to first stage. (Following the first stage the soft closure kicks-in). I am aware of the Potentiometer in the Hydraulic system which is supposed to send a signal that the lid is closed and the hydraulic pump must stop and now the PSE system must take over. (I actually think it does) However this potentiometer is not adjustable. I am aware of the synchronisation procedure programming the computers with position limits information (Also from the potentiometer)but I have synchronised many time but still the lid does not close fully. The odd thing is that sometimes it suddenly works ones 100% and then it does not close again. The hydraulic fluid in the pump is on the right level, I checked. I read many articles about the systems but cannot find a solution but pressing the lid close by hand. Anybody experiencing the same problem or can give me advise to a solution. in brackets I add some crucial information I forgot: (When the trunk lid stops at the lock catch and not locks and when I then push the lid by hand to close it fully I can hear the hydraulic pump starting up again and run like 10 sec before switching itself off)

 

Your hydraulic system and pump are working fine, as is the delayed release from the trunk open button in the door. The PSE takes over at the point your trunk stops. This is a fairly common problem and can typically be resolved by removing and reinstalling fuse 57 (or 62, I don't have the book in front of me). The fuse box under the passenger rear seat, behind the floor light, will contain the fuse. It is in the yellow block. Take it out, make sure it is good, and reinstall. Then go try the trunk.

 

Hi Ryan,
Your prompt respond is most appreciated.
I will try the fuses again tonight. I say "again" because I got a slight dilemma. The under the rear seat fuse box layout differs for all shown on the forums and also differs from the layout on the fuse chart in my cars tool box. (The two perpendicular fuse blocks either side of the main block are not there)


I found the below description on another web side, referring to different numbers.
Please do not se this as criticism but only as something what confuses me. Perhaps you can shed some more light on the matter keeping in mind that my car is a right hand drive made in Germany.


So, let’sanswer the questions to the last two posts first. The voltage supply to the PSEpump and the hydraulic pump do not come from the rear SAM control module, onthe contrary, the voltage supply to the PSEmodule is via fuse number 62 - which is a 20 ampyellow fuse and is found in the same fuse-box that I provided earlier. Thevoltage supply to the hydraulic pumpis via fuse number 57 in the same fuse-box,the two micro relays are switched on/off from the PSE control module. Have alook again at the fuse-box layout and you will see the fuses clearlyidentified, more on this later.


Your help id mightily appreciated and I look forward your reply.


Cheers
Len de Krou (Dutch with PPL - that's why flydutch)

 

The fuse Ryan refers to sits behind the rear passenger seat light. You will need to pull the lens out in order to see the fuse. The yellow fuse controls the PSE pump. It will reset the pump. However, if the problem returns then you have something else that may be causing the issue.

Do you hear a hissing sound when the trunk is trying to close? Your problem could very well be the trunk lock actuator. They sometimes have a tendency to crack and the air pressure escapes.

Check out this video and see if it is similar to the problem you are having.

 

The fuse you are referring to, only resets the pump and it does not fix the problem. There is the trunk actuator that may be leaking, the pump itself or any of the lines. My trunk actuator itself was broken just like the video above and I replaced it with a Brand New one from the Dealer. Unfortunately still doing the same. The PSE system it's actually the worst think that I do not like about my W220

 

Hi John,
Thanks for your help. It is damn tricky problem as many parts play a role here. I did that check and found that the main air supply pipe to the actuator was broken where is goes to the spring loaded devise what keeps the wires and pipes under tension between lid and the body. When I fixed it I disconnected the ram from the lid and operated the system by pushing the lock lever to the first stage by hand and the lock closes and releases while I watched it. I did realise that disconnecting the ram from the hinge would through out the synchronisation but having followed the synchronisation procedure did not solve the problem. I will though strip it apart again and check for leaks again but that the hydraulic pump stops before it has driven the lid fully home so to speak bothers me.

 

If you are in a RHD, I think your fuse box will be on the driver's side rear. This could explain the differences? I personally have no experience with the RHD layout, but I am pretty sure the fuse box will be in the same spot.

Very common problem, and something that should be checked if things are apart, but if that were the problem, the trunk would not open from the electronic buttons. It would need to be opened via the key. That actuator is what pops the latch open.

Pulling that fuse and reinserting has been proven to solve this problem many many times. I'm not saying that it is 100% the cause of this issue, but it is the MOST common solution by far.

 

Your hydraulic system is acting appropriately. Reset the PSE via the fuse. If that doesn't work, check into the microswitch mentioned below (S88/3).

 

When you go back in check the trunk lock actuator. If it is cracked then you will need to replace it. It works the same with doors (different type of actuator). However, with the doors you will usually hear a hissing sound like air escaping. I have had a couple of these go on my doors and it is usually the white plastic cap that cracks.

That thing is under a lot of pressure and after years of wear the plastic has a tendency to crack. I tried sealing, taping, gluing but they would only work for a short while.

 

issues with the trunk not functioning properly.
The fluid in the reservoir is black, the lid will close but will then open 1/2 an inch on the right side/passenger side, if I press the trunk button the motion will stop, I can then press on the lid to close it but I still have to press the right side to fully close the trunk lid.
Is the fluid the problem?
How do you remove the reservoir safely without breaking it, it is stuck to the main pump body?
do I need to unplug the fuses mentioned 57 and 62 and reconnect them ?
Thank you
Serge
this is for a 2003 S500

 

If you search my nick on both forums you will find the procedure for fluid replacement and trunk lid stop adjustment.
Merry Xmas!

 

Please give me your NICK LINK
MUCH APPRECIATED
Serge

 

you click on my nick and search on both forums

 

Click on his name at the left

 

"nick" = nickname = user name

 

Change the fluid to Pentosin CHf 11S ( the green stuff), same fluid that is used for the ABC and Power Steering pump.

 

That's funny because mine does the same thing. It closes and then the passenger side near the rear windshield it will lift about 1/2 inch. It will close itself within 5-10 minutes though...

 

I had the famous "lift up problem". However, I never made any adjustments on the trunk lid to fix it. I just replaced the struts (because it would slowly creep down while in the upright position), replaced the hydraulic fluid, and reset the trunk by using the button on the door. To do this just shut the driver's door, turn the key to position 2, and hold the trunk button down for about 10 seconds. Hold the button DOWN towards the front of the car.

 

So did that fix the problem ?? I replaced the shocks as well because they would come down on me as well but never tried resetting the trunk. When you are doing the reset, does the trunk have to be open or closed ?? Thanks.

 

I reset mine with the trunk closed. However, something kind of weird happened. After resetting if I close the trunk with the button on the trunk lid everything works perfect. If I use the button on the driver's door it acts a little weird but eventually closes. To solve the problem I just use the button on the trunk to close. Everything works ok if I open the trunk with the door button but for some reason it just doesn't like to be closed with that button. I haven't spent any time trying to figure it out.

 

The trunk lid raising on the right corner next to the rear glass is a common issue on cars with the power trunk lid

http://www.edmunds.com/mercedes-benz...trunk-lid.html

 

That's exactly what happens to my trunk Tusabes

 

I am having similar issues with my 2003 S500. The trunk started not closing and opening all the way and continued to get worse. The air system seems to be working fine so I did the fluid change in the hydraulic pump as described in the forum. It was indeed low. Now the trunk hydraulics will come on close the trunk and the air takes over closing as it should. The problem: When opening the air system comes on and unlatches the trunk but the hydraulic pump never comes on. So everything working fine closing but no hydraulics opening.

Does anybody know what I need to do?

 

Was you able to resolved the hydraulic pump issue? I'm having similar issue and thinking it's either the V23074 relay or the signal wire. Appreciate if you can update.

 

Never mind. I found the problem with my hydraulic pump. There was no signal to tell it to turn on.