SL/R230: Have Trunk Soft Close / Trunk Assist problems. Here is how to fix DIY.
Super Member
Joined: Sep 2018
Posts: 746
Likes: 184
From: Melbourne, Australia
2005 SL 500 R230
I just did mine again.
The best advice I would give anyone repairing their boot lock is don't use epoxy. It gives the appearance of grabbing tightly on to the plastic but doesn't really bond; you can pick it off the plastic where it sort of peels away in a lump.
One of the pieces I had glued a year or three ago had come loose off its end and caused a leak.
I used Loctite Prism 480 cyanoacrylate and fast spray activator this time on all six tube ends (there are six - don't miss one) and now it seems to be perfectly airtight.
I just looked up the baking soda and super glue technique which should yield similar results.
The best advice I would give anyone repairing their boot lock is don't use epoxy. It gives the appearance of grabbing tightly on to the plastic but doesn't really bond; you can pick it off the plastic where it sort of peels away in a lump.
One of the pieces I had glued a year or three ago had come loose off its end and caused a leak.
I used Loctite Prism 480 cyanoacrylate and fast spray activator this time on all six tube ends (there are six - don't miss one) and now it seems to be perfectly airtight.
I just looked up the baking soda and super glue technique which should yield similar results.
Junior Member
Joined: Apr 2022
Posts: 71
Likes: 15
Sl600
Am I crazy for just replacing the leaky part..?
Hello everyone. Summers here and time to drop the top. My soft close function works only sporadically, like many of ours….ugh
ive read all of the solutions and attempted solutions here and have concluded it’s best just to replace the leaking part. Does that make sense….just not technically inclined nor open to continual frustrations!
You thoughts please?
ive read all of the solutions and attempted solutions here and have concluded it’s best just to replace the leaking part. Does that make sense….just not technically inclined nor open to continual frustrations!
You thoughts please?
Super Member
Joined: Sep 2018
Posts: 746
Likes: 184
From: Melbourne, Australia
2005 SL 500 R230
Well, we're all different, and if you don't have those sorts of skills then you're locked in to either getting an MB dealer to replace the lock, getting an independent to replace it, or getting someone to remove and repair it, with the third option being the most logical. It's a pretty easy job, but read my comments about not using epoxy on the leak points.
Option one or two are going to be expensive. Option three you can do for the cost of the cyano.
Option one or two are going to be expensive. Option three you can do for the cost of the cyano.
Junior Member
Joined: Jan 2021
Posts: 32
Likes: 5
From: NJ
2005 SL 600, 2004 Jaguar XKR, 1998 Corvette, 1975 Porsche 914
This is a great thread but I have a question for those who have done this. I have the latch assembly out and am testing for leaks. The only air i feel or hear is coming from near the side of the latch itself not anywhere near the ports with the ball bearings or the "puck". Is that normal or should any air leak be attacked and plugged?
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Super Member
Joined: Sep 2018
Posts: 746
Likes: 184
From: Melbourne, Australia
2005 SL 500 R230
If you can connect a low pressure air source such as a bicycle pump to the air inlet which shouldn't be too difficult then you can put a few psi of pressure into the lock.
Mix up some dishwashing liquid in water in a spray bottle, spray it around the lock and watch for the bubbles. You'll find them pretty fast. However all six ports where the ball bearings are pressed in should be glued up with cyano as a matter of course - don't bother reinstalling the lock unless they're all glued up.
Mix up some dishwashing liquid in water in a spray bottle, spray it around the lock and watch for the bubbles. You'll find them pretty fast. However all six ports where the ball bearings are pressed in should be glued up with cyano as a matter of course - don't bother reinstalling the lock unless they're all glued up.
Last edited by Tom Manning; Jun 12, 2022 at 10:38 AM. Reason: typo
Junior Member
Joined: Apr 2022
Posts: 71
Likes: 15
Sl600
Good morning. It’s a bit surprising to see how many of us are afflicted with this issue, but heartening to also see how many of us are willing to tackle problem personally. I know the limitations of my technical skills and decided to have my independent Mercedes specialist just replace the unit, $500 total. Best $500 I’ve spent recently, gives me peace of mind on the road that if confronted by rainstorm I can raise the top reliably.
Junior Member
Joined: Jan 2021
Posts: 32
Likes: 5
From: NJ
2005 SL 600, 2004 Jaguar XKR, 1998 Corvette, 1975 Porsche 914
This is a great thread! I removed and fixed my latch mechanism. Mine was leaking not from the ball bearings my leak came from the side of the latch itself. I sealed that AND the ball bearings with JB Weld epoxy. Works great. This is rteally a very simple project. Thanks to all who hav eposted to this thread over the years!
Member
Joined: Oct 2018
Posts: 86
Likes: 17
SL500 R230
I've been trying to fix the soft close on my boot latch for months. I've tried two different types of glue. Leak tested twice with foamed washing up liquid. Every time I put it back it works for anything between five minutes and several weeks. I was certain I had fixed it after the last time three weeks ago and it still worked yesterday evening. This morning it's stopped again. I think i need to give up.
Member
Joined: Apr 2009
Posts: 124
Likes: 22
2004 sl600
Thanks to all who contributed to this thread. I epoxied my ball bearings and also the hockey puck needed epoxy repair as well. Now the soft close is working on my 2004 sl600. Wish it had power trunk open and close but that seems to be cost prohibitive or not really possible.
funny thing with the fuse is the order on my fuse block did not match others who posted. I looked at the amperage and eventually figured out which one to pull based on that and the pump reset no problem. So for those who could not get the pump to reset by pulling the fuse, check to see if your fuses are in the same order or not. The fuse blocks are color coded and seem to be able to be moved.
funny thing with the fuse is the order on my fuse block did not match others who posted. I looked at the amperage and eventually figured out which one to pull based on that and the pump reset no problem. So for those who could not get the pump to reset by pulling the fuse, check to see if your fuses are in the same order or not. The fuse blocks are color coded and seem to be able to be moved.
Junior Member
Joined: Jul 2021
Posts: 25
Likes: 13
From: Clearwater, Florida
2004 SL500
What a great thread. Thanks to all.
Since I had this problem too, I did the project, but mine was a little different. It was obvious the lock assembly had been replaced (tye-wraps were gone, new looking, no cracks), but I sealed the bearing holes anyway for the future. I also thought a little epoxy on the surface near the end would slow the escape of plasticizers and maybe extend the life of the part.
In the past, the electronic fuse tripped the fuse 71 circuit, seemingly when I left the lid slightly open for a while, and the red light on the drivers door came on, like everyone else. Pulling the fuse for a short while always reset the electronic fuse, like everyone else. But here is where the gremlin snuck in after the "repair". Although the soft close worked as it should, the red light came on anyway and refused to be affected by fuse 71. But, the soft close still worked. Then a little later, the red light went out. This seems to be an intermittent problem, maybe a sensor right on the edge. I am assuming if the light is on, the top will not function, so it is imperative to find the gremlin. Any ideas?
I am wondering if I accidentally moved whatever it is that signals the lid is closed. What and where is the switch/sensor that tells the computer that the lid is closed? Anyone know?
Also in this process, I failed to figure out what the long contoured rod that connects to an arm with a snap ball does for the system. It is possible that is the source as I had difficulty with it? Anyone know?
Sure hope someone has the answer as I now have zero confidence in the reliability of being able to move the top.
Since I had this problem too, I did the project, but mine was a little different. It was obvious the lock assembly had been replaced (tye-wraps were gone, new looking, no cracks), but I sealed the bearing holes anyway for the future. I also thought a little epoxy on the surface near the end would slow the escape of plasticizers and maybe extend the life of the part.
In the past, the electronic fuse tripped the fuse 71 circuit, seemingly when I left the lid slightly open for a while, and the red light on the drivers door came on, like everyone else. Pulling the fuse for a short while always reset the electronic fuse, like everyone else. But here is where the gremlin snuck in after the "repair". Although the soft close worked as it should, the red light came on anyway and refused to be affected by fuse 71. But, the soft close still worked. Then a little later, the red light went out. This seems to be an intermittent problem, maybe a sensor right on the edge. I am assuming if the light is on, the top will not function, so it is imperative to find the gremlin. Any ideas?
I am wondering if I accidentally moved whatever it is that signals the lid is closed. What and where is the switch/sensor that tells the computer that the lid is closed? Anyone know?
Also in this process, I failed to figure out what the long contoured rod that connects to an arm with a snap ball does for the system. It is possible that is the source as I had difficulty with it? Anyone know?
Sure hope someone has the answer as I now have zero confidence in the reliability of being able to move the top.
Junior Member
Joined: Aug 2022
Posts: 32
Likes: 1
2005SL500
Have Trunk Soft Close / Trunk Assist problems. Here is how to fix DIY
Hello again. I'm waiting for my PSE replacement impeller. Meanwhile, I put the repaired air controller assembly back in the trunk thinking I was done with it. Now for some reason my remote won't unlock the trunk lock- something that had never happened before. I tried to manually open the trunk using the key and that wouldn't work either. I have the trunk in the service position because I need to replace the right load assist cylinder. I decided to remove the inside trunk cover so I could see the relationship between the air controller and the key lock mechanism. Here is where the linkage comes into play. When reinstalling the air controller assembly I had just put the linkage in any way it would go - not a good idea. At this point I would say I don't think I could be assured of putting that linkage back in the car correctly if I didn't do it from the rear. I had to adjust it from the beginning to get the key and trunk handle to open the trunk like it is supposed to. Now if I could just figure out why my remote won't unlock the lock from the soft close position as it had been doing. The PSE pump works so I'm thinking the wire connectors on the air controller are not working properly because I am getting no air to the air controller when I push the unlock button.
MBWorld Fanatic!
Joined: Mar 2018
Posts: 1,442
Likes: 260
From: Netherlands
2005 R 230 SL350 (M112 3.7). Sold the 1966 W113 230SL recently
I think you mean the part that enables you to open the trunk, using the key (turn the key, hold it there and pull the grip).
Junior Member
Joined: Aug 2023
Posts: 17
Likes: 7
From: Maryland
SL55AMG, ML63AMG
I know your post is old but I just found identical pieces of plastic fall out when I removed the latch mechanism. Where did they come from - I can’t tell and seems the only option is a total new complete mechanism? Thanks
Just the other day I had a similar issue as Nick's original problem, where the trunk of my Wife's 2007 SL550 suddenly stopped working. It wouldn't open in the unlock position with the handle or the remote. I had to use the key, turned completely to the left to open the trunk, and after a bit of inspecting I could hear air escaping at the latch mechanism. Here is what I found.
Following Nicks original post I removed the truck latch assembly. During the removal a few small pieces of black plastic (see below) fell out from the trunk carpet liner, which came from the small air actuated plunger. Apparently over time the plastic becomes brittle enough that the small clips that hold together the air actuated (key-less remote) plunger assembly together break, then separate enough to allow for an air leak, consequently (I believe) the pump will time out.
Attachment 286194
Attachment 286195
Attachment 286196
The bad news was I couldn't repair this with any epoxy or glue to satisfy my **** retentive ways, so I opted to buy a replacement unit from my local MB dealer ($317.00). The good news was following Nick's original post, the replacement literally took me 20 minutes.
Nick great post, hope this additional tidbit helps anyone else with a similar problem.
Following Nicks original post I removed the truck latch assembly. During the removal a few small pieces of black plastic (see below) fell out from the trunk carpet liner, which came from the small air actuated plunger. Apparently over time the plastic becomes brittle enough that the small clips that hold together the air actuated (key-less remote) plunger assembly together break, then separate enough to allow for an air leak, consequently (I believe) the pump will time out.
Attachment 286194
Attachment 286195
Attachment 286196
The bad news was I couldn't repair this with any epoxy or glue to satisfy my **** retentive ways, so I opted to buy a replacement unit from my local MB dealer ($317.00). The good news was following Nick's original post, the replacement literally took me 20 minutes.
Nick great post, hope this additional tidbit helps anyone else with a similar problem.
MBWorld Fanatic!
Joined: Jul 2010
Posts: 4,359
Likes: 229
SL55, S500
The trunk locks without the soft close and the top will operate fine. You just need to close it with more force. Both hands on the left and right side and slam down. It will lock. I’ve been doing this method for years now.
MBWorld Fanatic!
Joined: Mar 2018
Posts: 1,442
Likes: 260
From: Netherlands
2005 R 230 SL350 (M112 3.7). Sold the 1966 W113 230SL recently
My mantra: slamming the trunk lid may eventually crack or dislodge the 3rd stop light. Water may seep into the trunk lock, affecting the electric parts in there.
MBWorld Fanatic!
Joined: Mar 2018
Posts: 1,442
Likes: 260
From: Netherlands
2005 R 230 SL350 (M112 3.7). Sold the 1966 W113 230SL recently
The plastic pieces on the photo's have broken away from the puck. That may cause the puck to leak air. Strap the puck tightly with tie wraps. I did ead that worked for Rudeney,
Junior Member
Joined: Nov 2022
Posts: 18
Likes: 4
2007 R230 sl550
Took a working SL 550 (2007) trunk and decided to epoxy the ball bearings.
Everything works that I can tell. Including the 2nd latch. It opens fine and closes fine. My door locks are quicker.
I disconnected the trunk battery for a few minutes and pulled the 54 fuse (20amp). I pulled and reinstalled the latch mechanism and all seems right.
But the car is convinced my trunk is open (it is not). I can't raise the top and I get a red light when moving more then a few miles per hour.
Any other ideas to try?
>>> quick update and hope this helps someone. I don't remember doing this but i had the trunk set to valet (manual key). Somehow in the process of me trying to figure out how it all works probably.
And you can't raise the top in valet mode. Anyhow I fiddled with the manual key and latch and something got jiggered back to where it was supposed to be and voila. It seems to work. Hoping not going to be an intermittent issue but seems good so far.
Everything works that I can tell. Including the 2nd latch. It opens fine and closes fine. My door locks are quicker.
I disconnected the trunk battery for a few minutes and pulled the 54 fuse (20amp). I pulled and reinstalled the latch mechanism and all seems right.
But the car is convinced my trunk is open (it is not). I can't raise the top and I get a red light when moving more then a few miles per hour.
Any other ideas to try?
>>> quick update and hope this helps someone. I don't remember doing this but i had the trunk set to valet (manual key). Somehow in the process of me trying to figure out how it all works probably.
And you can't raise the top in valet mode. Anyhow I fiddled with the manual key and latch and something got jiggered back to where it was supposed to be and voila. It seems to work. Hoping not going to be an intermittent issue but seems good so far.
Last edited by JohnHunt83; Aug 28, 2023 at 01:13 PM. Reason: update
Junior Member
Joined: Aug 2023
Posts: 64
Likes: 17
From: Dominican Republic
R230 SL500
I'm dong this repair now. Found a leak in exactly the same place as everyone else. But when I tried to disconnect the yellow pipe connector, the barb broke off inside the hose. Does anyone have the part number of those grey pipe connectors? They are a real fiddle to undo without breaking.
