John CL500

Although I have seen this posted on numerous occasions, I have not found the solution to my problem:

The automatic trunk does not open the trunk.
Neither the Key FOB or the interior lift switch will do it.
The lock/Latch DOES release the the trunk...but no lift.
The lift switch on the drivers door used to light RED when I pulled or pushed it....now...no lights.
The trunk WILL close automatically when I hit the RED trunk button on the bottom edge of the trunk.

I have tried pulling all fuses associated with the remote trunk release....no go.

I have taken off the trunk lid cover and saw no obvious problems there.

I DO hear air moving when I hit the trunk release on the key....but I do not feel any air leaking out..

Recently tried something different.

I hit the trunk release button on the key to unlatch the trunk
I then lifted the trunk manually (about six inches)
Then I hit the release button again and it went up automatically...as it should.


PLEASE....IF YOU HAVE FOUND A SOLUTION TO THIS COMMON PROBLEM.....Email me at johnbosmans@yahoo.com

Thanks ALL!

P.S. I have posted this on Benzworld.org also...NO SOLUTION THERE

John CL500

And here I thought was a very common problem...???????

Racin_fool

If you hear air leaking when actuating the trunk with the key or one of the switches, then your latch is most likely leaking air (which the PSE pump will eventually shut off and disable). You shouldn't be able to hear any air leaking with it working properly. As for the problem with the trunk not opening/lifting when operating, I would check the wiring around the trunk lid hinges to make sure one or more of them aren't broken.

wigging

I just posted a similar problem on my 04 cl55.... except, I cant get the darn trunk open at all. Even with the key. I can turn it to valet/locket but that does help me. In the open/neutral position, I push up on the lock but the trunk wont budge....

see my post about 10 slots newer than this if you think you can help.

didnt mean to hijack- whats with these trunks seems like lots of folks have this problem.....

saintz

There are several problems that can occur.

The hydraulic pump that opens and closes the trunk can lose fluid. In this case, the trunk will pop an inch open, no more. It won't auto close, either. You will hear the pump running dry trying to open it. Fix is to remove the pump (under the battery) and refill the fluid reservoir, and patch the leak if there is one.

If the trunk won't open at all, the pneumatic system probably has a leak. Open with the key, remove the trunk panel, and JB Weld whatever is leaking back together. I've had the bladder break twice.

You can also have the electronics get a cut wire or other issue. This will generally manifest in things like no light coming on for the trunk buttons, the buttons not working, etc.

John CL500

wigging - no prob on the hijack....I still havent found a solution.

saintz - Since the trunk does auto close with the red button, I will assume its not the pump fluid.

Since the trunk does unlatch and open after lifting it 6 inches or so and then hitting the open trunk button on the key fob, I will assume its not the Hydraulic pump.

So that leaves me with a likely electrical problem. I would probably start at the mesh encased wires that go from the trunk into the vehicle itself????

Does that make sense?

saintz

You might have trunk safety mode turned on. This causes the trunk to only crack open and then you have to press again to open it all the way. It's to prevent the trunk from hitting something in a parking garage.

Try holding the trunk open button inside the car for over 5 seconds. This should reset it to open all the way.

https://mbworld.org/forums/s-class-w...-half-way.html

John CL500

Saintz....I thought so also.....tried that.....no luck. I guess I am back to checking the wiring.

John CL500

Success!

Thanks to Wig and Saintz.....

Finally got in to the Trunk Latch and discovered that it was indeed the Pump Actuator (THE DREADED PUCK) that was causing the problem.....It was cracked in several places.

So i took the following steps to fix the problem.

First, Cabled tied the puck tightly....
Next, Epoxy all around the seams....
Last, Good Old electrical tape to give it the extra sealing power....

Re-Installed the puck......and.............power assist trunk works!!!

P.s. This fix also corrected my drivers side door soft close problem!

240M3SRT

Congrats on the not too expensive fix. Where is the pump actuator located and what does it look like?

John CL500

Behind the Trunk Lid Cover....in the Trunk latch assembly...

Trying to get a picture of it....will post it soon...if you need further instructions/info just let me know....I am glad to help.

John CL500

Pic of PUCK

240M3SRT

Nice job! Thanks for the pic.

Gotta love epoxy.

thesheikh

Hey John! Thanks for this thread. I have the same problem with my e500. Im going to try and check this out. Where exactly is the pump actuator located?

DjSpin

Thank you so much for the very helpful info..I had the same problem and flowed the steps and its working again.

mf219

any chance you could post a pic of where the "puck" is located?

Anthony PNC

John - great stuff, I have the same issue right now. My technical issue is, how do you remove the puck? Do you have to pull out the entire lock assembly or can you disconnect the puck while the assembly is still attached? I got in there today and couldnt figure it out.

biker349

can you buy the puck seperately?

Anthony PNC

No you can't buy it separately.

awiner

Actually I have found a supplier for the piece (Boot Closer Assist Upper Cap) separately as well as the door close assist pieces if needed. If you want info feel free to PM me.

tonydt1g3r

thanks for this thread. The puck was broken like stated above. I used some permetex plastic weld and put it back together. saved me some $ thanks again

CL500

Can anyone explain to me how to remove this puck thing?

As of now - my doors won't autoclose anymore and I'm unable to remotely lock the car with the key.

I checked the 20A fuse (under the rear seat) and it was blown. Put a new one in, and I can hear that the pump starts up - runs for a while and then blows the fuse again..

awiner

The trunk puck or the door puck ? This thread is in regards to the trunk. There is another thread about the doors that has more info.

CL500

As far as I could understand the problem I'm experiencing has to do with the pump/puck - in the trunk.

The doors AND the trunk won't softclose anymore. I'm also unable to lock/unlock the car with the key remotely (central locking).

I can open the trunk mechanically, and also the drivers side door.. (at least when it's not frozen).

awiner

For the trunk, you need to remove the rear plastic trim that holds the electronic close and/or lock buttons (on electronic optioned trunks).

Then remove the felt covered trim panel from the lid.

You will then see the pneumatic locking unit. To remove it, remove the locking rod and associated screws.