lganski

Hi all,


Recently I had to replace the battery and alternator in my car. I had to open the trunk with the metal key and push it open. The right side hinge did not want to open so I had to pull it up till it released. After that I noticed that the right would not fully go back down when closed. It is raised around a half inch on the right hinge when closed. Also after the soft close engaged the trunk assist would keep running. To stop it I would have to lock the car and press the release button and it would shut down.


The other day I had the trunk open and went into the house to do something. My wife did me a favor and pressed the red button on the lid to close it. When I came back the trunk was closed and the trunk assist would not activate. I pulled the three related fuses to try and reset any time out that may have activated but no luck. It is still dead. So now I can't use the trunk because it won't open except for a few inches.


I wanted to disconnect the piston from the hinge and unplug the pump till I could deal with the problem but now I can't get it to open to access it. I don't want to force it and bend the trunk lid. So here are my questions....
Could I still be dealing with a shutdown situation with the pump? If so what would be my next move. Since I have never seen the setup of the hinge and piston is there a way to convince it to open mechanically without damaging my trunk lid? Does anyone have an exploded view of how it works? Thanks in advance. I have a 06 S430 4Matic.

ibeforreal

Iganski,
I experienced a similar problem a while back. My trunk would close but the passenger side of the trunk would lift up and make this grinding noise until it stopped or I hit the release button. I would have to manually close the trunk. Once it stopped gringing the upper passenger side towards the windshield would not be flush.

Initially I also thought my trunk hinge was the culprit but that turned out not to be the problem.

After further diagnosis I realized that my pump reservoir (under the foam padding) next to the battery did not have any fluid in it. Once I filled that up to the fill line, everything operated normally. I used regular transmission fluid but some others here have used pentosin.

What you might try doing to get the trunk to open is pull the YELLOW fuse that is hidden behind the footwell lamp under the passenger seat. Just pull the lense cover out and you will see the fuses. Pull the yellow fuse out for about 20 minutes. This fuse resets the PSE pump which controls the door soft close, locks, headrests, and the trunk.

I would try all of the above before tinkering around with that hinge. If the hinge is replaced it has to be aligned properly and I would only trust a body shop or MB dealer to do this unless you have the experience.

Hope this helps.

lganski

OK, I pulled the fuses and checked the fuse chart for others. They were out for hours since I was changing my tranny and transfer case fluid. No luck. I will try to lift the lid high enougt to get at the hinge bolts and see if i can take it off. I am speculating that the pump is dead. I hope it will take a wrench and not need a socket.

lganski

I got into my trunk last night. Finally got it open by gently talking to the hinges. It opened real hard. Unhooked all pistons and found out that the hinges were seizing up. Got out the WD40 and lubricated the hinge joints on both sides and worked the trunk lid till it would come down its self. Reconnected the hinge pistons and tested. That part of it is now done. I tested the open assist and as I expected it did not work. I pressed the red close button and could hear the relay activate but nothing. I left the assist piston disconnected for now. I will be checking the pump connector for voltage when I get a chance.


For all of you who have a slow closing trunk make sure you keep the hinges lubricated!

wallyp

Wholeheartedly agree on lubricating the hinges - trunk and hood. However, WD-40 is a pretty temporary lubricant - I much prefer using engine oil.

lganski

Thanks, I wanted to get them working quickly. I will use engine oil because WD40 does not last very long.

lganski

Hi all, Just an update on my trunk assist problem. I checked voltage at the connector and when I pressed the close button I would get voltage, when I pressed it a second time it would shut off. So it looks like voltage is getting delivered. I hooked my pump up to the battery and it would not run. Looks like the motor crapped out. The motor is sealed so I have not tried to take it apart yet. If you check it with an ohm meter it reads very high so it looks like it is open.


I am now looking for a replacement assembly. I know there are at least 3 members out there that have one. Two cars being parted and one spare assembly. I would be interested in buying one for the right price. Please PM me if you have one.