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Have Trunk Soft Close / Trunk Assist problems. Here is how to fix DIY.

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SL-Class (R230) 2003 -- 2012: Discussion on the SL500, SL550, SL600

Have Trunk Soft Close / Trunk Assist problems. Here is how to fix DIY.

 
Old 11-18-2010, 08:46 PM
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A related item I found: If the latch works fine, but the red auto close button doesn't work (assuming you have this feature) and/or when you unlock the trunk it just sits there (instead of popping up), then your hydraulic pump is leaking.

The latch uses pneumatics (air from the PSE pump) to lock, unlock, and "soft close" (meaning to suck a door or trunk that is almost closed until it is fully closed).

However, there is a separate hydraulic (oil) pump used by the auto close feature, which engages when you press the red button in your trunk. The pump is located either under the battery (on a W215) or by the battery (in a W220 and I think also in the SL models), behind the passenger side trunk shielding. Remove the plastic shielding, locate pump, remove. The transparent plastic container is a reservoir, and it's probably empty. Remove and refill with oil (ATF or power steering should work). Now use the system and you'll find the leak. Either it's slow, meaning you just need to refill it, or it's gushing (probably from one of the fittings on the piston the hoses attach to. I used QuikSteel to "caulk" the fitting to stop the leak. Refill the reservoir again, and your auto-close should now be working.
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Old 05-24-2011, 09:59 AM
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E 63 Renntech, E55 Renntech, SL65, SL 55 030, ML, bunch of old ones--they come, they go...
Hey ,

this is a great post. I know it hasn't been touched in a while....but I overloaded my trunk this weekend, and pretty sure that I need to replace/reset the fuse for the soft close. I have the panel off and can see them all, but cannot identify which one--I know it's a 20 amp one, but which one? This isn't a car you just randomly want to replace fuses in! Thanks for your help.
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Old 05-25-2011, 12:45 AM
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Thanks Nick!! Great to see a DIY actually working. I followed all the steps and my trunk now has a fully functional soft close! World of difference and saves me a lot of frustration (previously the car would frequently tell me to close the trunk if I wanted to let the roof down).

Four things I learned in the process:

1) you really need to spend some time to find a good plastic epoxy glue in order for this to work. I misread the description and bought Gorilla Super Glue but that did not work. The Plastic Epoxy I bought next did the job.

2) In my case, it was sufficient to only apply the epoxy to the inside (to cover the leaking ball bearing). The outside was not cracked and could do without glue to keep it clean.

3) it is WAY easier to fill the ball bearing ports with glue if you detach the whole air compartment. Instead of using bent pieces of wire to reach the hard-to-reach ports, you can simply disconnecting the green, yellow and black air tubes and then press the two clip-hooks inwards to take out the whole compartment. It is small and gives you easy access to all properly glue all 6 ports.

4) when I re-installed everything I made an error and had the black air tube block the latch release. The effect was that the trunk would soft-close but immediately after open again. Pushing back the black air tube and strapping solved this.
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Old 07-01-2011, 12:03 PM
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2003 SL55
My soft close just stopped working last week. working the open lever did open the trunk. Came across this thread. Reset the consumer battery and the soft close started to work again.

So I have my latch pulled out. I am listening for all I am worth, but I can't hear any air leaks. I hesitate to start gluing this dude up if I can't hear a leak. However, it does appear that there are cracks on the top of at least one port, and all of the ports are showing stress in the form of the plastic being lighter grey right around the bbs.

For those of you that have gone before me, a few questions.

How many uses of the soft close would you get before the e-fuse would trip? I have cycled it a dozen or so times in my hand listening for the air leaks and it is still working...

What brand of glue did ya use?

What is the trick to disconnect the air delivery hose?

And most importantly, how loud were the leaks? I am tempted to get my leak detector fluid or some windex but that is a messy process....

Thanks!

Slider
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Old 07-02-2011, 02:05 PM
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Well, I never heard an air leak. But I took it all the way out and glued it up anyways. I could see what appeared to be stress cracks and stretching so since it was in my hand....

Put it back together. Trunk seems to operate fine.

Fired up the car, and the ESP is not available. Also, when I climb in the car and shut the door, the window doesn't go back up an inch like normal.

Uh oh...

So now I have pulled the consumer battery off and will leave it off for a few and see what happens.

Anyone have any other thoughts, please post!
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Old 07-02-2011, 02:14 PM
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resetting the consumer battery didn't fix the door window issue...
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Old 07-02-2011, 02:51 PM
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Originally Posted by Slider5150 View Post
resetting the consumer battery didn't fix the door window issue...
There are a few things that need to be reset after disconnecting the battery. Windows, seats and something to do with turning the wheel from all the way right to left - might be esp. Check your owner's manual - it should detail it. I know for the windows you have to put them down, then up (all 4) and continue to hold the switch in the up position for 2 sec. MB calls it synchronizing. The seat as I recall is all the way up then all the way back.

I did what you did and for me it resulted in a TeleAid malfunction - and $100 labor at MB to reset. MB recommends NEVER disconnecting the consumer battery. To change it you need a charger attached. Fun cars but way overengineered.

Good luck!
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Old 07-05-2011, 01:04 PM
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Read your post and it got me thinking.

So I shut the trunk, which pulled itself shut nicely. Then I cycled the roof down and up. That fixed the windows.

Drove it about 500 feet, and the traction control re-activated.

Trip the MB only cost me 5 bucks for 2 clips!!!

I am still not totally convinced that my problem was a leak in this mechanism, but in 6 months, if it is still running, I guess we will know. There were cracks there, but nothing obvious, and even with careful listening, I couldn't hear any air leaking out. But, all things considered, fairly easy repair. Really not too hard to pull the component with the bbs in it all the way out, I would recommend doing that to folks reading this.

Great thread, it covers pretty much everything you need to know! There are two push-clips holding the carpet in place on the trunk lid that you will have to find and pop thru before you can get your hands up in there, and the trunk latch is a little ball and socket deal that pops apart with a twist at the top. (kinda like my shoulder...) I found twisting the socket that is on a threaded rod to be the easiest way to dislocate the connection. Then you can push the latch mechanism up thru the cutout in the lid and take it out.

When you start testing the unit make darn skippy sure you know where your fingers are before popping the trunk latch to the soft close position. Don't want to think about the damage you could do if the mechanism closed on your finger....

Other than that little bit of pay attention or it will hurt a lot, this was a really easy repair. I went slow and spent about an hour and a half. But I only lost 1 clip and finished with no extra parts.

Thanks for the great instructions!!!!

Slider
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Old 07-07-2011, 02:29 PM
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This was a GREAT DIY savings
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Old 08-14-2011, 03:19 PM
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I replaced the latch, it was far gone and the plastic peice to hold the bar to open was cracked. Now when I close it the pump runs for about ten seconds. after 2 of 3 cycles it stops working. Any ideas?
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Old 08-16-2011, 09:21 PM
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I'm going to try the superglue fix in September, when I have a few days off from work to screw it up and try to fix it again. In the meantime your "disconnect the battery" trick worked in a time when I needed it most (9:00 pm with expected rain overnight and top stuck down!). If you ever come to Philadelphia I'd like to buy you a beer!
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Old 09-10-2011, 04:27 PM
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OK, finished on Thursday, let sit till Saturday all is well in MB world.

Trying for the life of me to figure out why after spending $125,000.00 that all they use is BS plastic. not ABS but Bull S--t plastic. LOL


for the allenjdmb Post. the fuse set for this feature is in the storage box behind the passenger seat, hard to see, but the bottom comes up with the two tabs on the floor of the box to the rear, pull it up and you will see fuses facing forward, the third from the left is the 20 amp #71 thats your puppy you are looking for.

thanks to all for the fix on this problem, I saved a small fortune and I did not call GEICO. LOL

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Old 09-10-2011, 04:50 PM
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I reset the roof and everything else and now the soft close seems to work fine after a week.
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Old 09-11-2011, 01:49 PM
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E 63 Renntech, E55 Renntech, SL65, SL 55 030, ML, bunch of old ones--they come, they go...
Careful....

On my 65, the third fuse was blank....it was the fourth. Better make extra sure. Might be different in the ROW. The fuse fix worked for a while for me, but ultimately quit, had to do the reseal fix suggested here....
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Old 09-12-2011, 01:17 AM
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Trunk issue

Hi Nick,

Just got a 2003, S500. Wehn I press the soft close botton, it kind of comes down a bit Fast (have to move out of the way) initially and then slow . It sits on the base but does not shut tight. Is this the same issue as you had?? WOuld I be able to try this on my ride as well or would it have a different type of mechanism?? Please help.


Originally Posted by NikleinR6 View Post
A common problem on many of our cars is the the trunk assist will randomly stop working one day, and you won't know why. You can unhook the convenience battery and reconnect, and the soft close function will begin to work again, but not for long. Eventually it will stop pulling the trunk closed again, and you will have to pull the fuse (or unhook the battery). This is only a temporary fix which could ultimately result in pump failure.

The problem with our cars is that the soft close latch is operated by air, and if there is a leak anywhere in the system, the pump times out, and the soft close function ceases to work until the system is reset.
So, on the latch mechanism, there are 4 air ports that mercedes plugged with small ball bearings. These bb plugs work fine when the latch mechanism is new, but as the plastic around them ages, it cracks where these ball bearings are. The cracks allow air to escape, and here is the problem.
The solution is to buy some $5.00 plastic epoxy, and glue the outside of the ports and the inside of the ports shut.
You will notice some orange silicone on the latch assembly. I initially tried to use silicone gasket maker to cover the ports, but quickly found out it was not strong enough , and the air pushed its way out. So make sure you use a strong plastic epoxy. Gorilla Glue makes a great gel (super glue) epoxy. I used it later...

In the next series of photos i will show you how to resolve the problem permanently.












After you pull the latch mechanism out reset your convenience battery, push the latch clasp in 1 click, watch as the pump actuates and closes the clasp fully, and LISTEN FOR AIR ESCAPING.. When you find the air leak, begin applying the glue there, but also apply it to the other ports just in case. Be generous..









You could take your car to the dealer and pay over $300+ to have a new latch installed, or you could fix it like i did in less than 30min and for less than $5.00
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Old 10-29-2011, 04:57 PM
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Very cool post guys. I will be trying this one soon...Thanks
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Old 12-13-2011, 06:17 PM
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Hi guys I recently overloaded my trunk this weekend and the soft close suddenly stopped, can you guys tell me if this is a normal issue? and do i have to do the DIY steps to fix it or is there a way to reset it. thanks guys
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Old 02-09-2012, 06:05 AM
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Epoxy

Epoxy glue implies resin/hardener type glue?
I am not sure how you actually epoxy glue the ball bearings or the vacuum hoses.
Do you remove the hoses & fill them up with epoxy glue?
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Old 02-12-2012, 12:18 PM
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Originally Posted by sifis View Post
Epoxy glue implies resin/hardener type glue?
I am not sure how you actually epoxy glue the ball bearings or the vacuum hoses.
Do you remove the hoses & fill them up with epoxy glue?

Absolutely DO NOT epoxy any hoses or connectors where hoses go. Please read the DIY again, or don't attempt this fix....
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Old 02-15-2012, 11:31 PM
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Where can I buy used control unit for SL500 03 model..
Part number: 032 545 04 32
The unit is found under the steering wheel
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Old 06-07-2012, 08:47 PM
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Great Fix, but I get "close trunk lid" dash message

Fix worked great, and now my 04 SL55 soft close works fine and trunk is closed tight. But before the fix, I could slam the lid hard and then lower the top. After the fix, I have the red light on at the remote trunk release switch and the "close trunk lid" message on the dash if I try to open the top. I can't get the computer to recognize that the trunk is closed tight. I've reset the codes by disconnecting batteries and jumping cables.

What sets off those warnings? If there is a sensor, where is it and how do you work around or replace it?
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Old 06-18-2012, 04:31 PM
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epoxy problem?

I am having the toughest luck fixing the stupid trunk.
i did all that you told me to do, except i used JB WELD.
Will this cause the following problem?

------ After covering all holes, I disconnected then reconnected the Aux Battery in the trunk next to the spare tire.

------ The soft close will work for 2 - 3 times, then stops working and i have to slap shut the trunk.

If using JB WELD vs. Gorilla glue is the problem, does anyone know how to remove JB WELD?? (lol)

Thank you!
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Old 07-24-2012, 11:13 AM
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Great write up! In the 9 years that I have owned my SL55, this is one of the few 'challenges' that I have had with the car.

I'm glad I decided to post a 600tt sale today. Otherwise I may not have seen this. Well done!

Last edited by IngenereAMG; 07-24-2012 at 11:18 AM.
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Old 07-24-2012, 05:20 PM
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This is a terrific post. I followed it, using a top quality plastic epoxy. Unfortunately the fix last only a couple of weeks. Then I did it again, but the fix lasted only a few closes. So I had to break down and buy a replacement closer for $265 from Ft Lauderdale MB online. Before the final fix, the necessary slamming of the trunk lid on the occasions when the closer broke down caused my third brake light to break out of the deck lid. Fortunately, I had that great plastic expoxy, which easily repaired the broken light, and allowed me to reinstall it (hand tight only, or it'll break.) All is fine now.
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Old 07-29-2012, 06:26 PM
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Guys, thanks for this great Post. I have a 2005 SL600 w 20k miles.... Soft close stopped functioning. Drove 3 days in Dallas at over 105 degrees F and it was brutal as I could NOT put up the top due to this error... Read you postings and tried the fuse pull trick first. On my model the fuse cover exists INSIDE the passenger side rear storage box. It is a flush mounted 6x8 " panel and is a bear to remove with your finger nails! Two clips offer positive closure so you must bend them simultaneously towards the front of the car...and pull up. Not possible...almost lost a nail ...of course sweating all over the place in this heat! Will clean that up later. Anyways, I grabbed the pliers from the trunk tool kit and used them to pull the clips once bent. Bingo! Easy Breezy. I pulled the 3rd fuse (from passenger side perspective) which was the only 20amp one nearby...5 secs to allow discharge of any electronics internally and then simply plugged it back in.
The moment of truth...put away the pliers...closed the back tire cover...and closed the trunk lid...and Voila! The soft close snugged up the trunk. Hopped in and fired 'ER up and hit the close roof switch ...it was a thing of beauty !!! All cool inside in 10 minutes flat as well.
Thanks for the fabulous fix Tip...I will give it a week or so to see if the vacuum assembly is OK, if not then off to buy one online and swap it out.
PS. Has anyone found a way to add the trunk lid hydraulic lift/close system? MB dealer says it is like $20K in parts and they do NOT want to attempt it. I had it on my 2007 SL55 AMG and it spoils ya Man!

Cheers!

Last edited by DallasDomn8er; 07-29-2012 at 06:32 PM. Reason: Typos
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