Hello... This vario roof subject, is in my opinion, the most annoying, worrying and concerning matter for every SLK owner...
At least it was in my case, so I wish that this article become useful to every DIYer who cannot send their cylinders to TopHydraulics or other service shop, or not willing to pay top money for new cylinders. In fact, I do not recommend to buy second hand cylinders as direct replacement, 'cause they will likely fail due to age of seals.
Fact is that oil seals and o-rings age by time and when working with hydraulic oil. Due to system pressure build up, the oil temperature goes up (physics laws), therefore there is a slow cooking of all the rubber involved and within the system.
Nothing can be done to prevent this, but replacing the seals. Luckly MB used nylon hoses instead of regular rubber hoses, so no problem expected there.
![Fluid Automotive design Liquid Automotive lighting Font]()
So as many users, we have bought the famous kits sold on ebay. Some are O-ring kits, some others use U cup Seals (with lips), which are way better IMO.
![Plastic wrap Plastic Transparency Carmine Packing materials]()
Here have attached the instructions that came in with the O-rings repair kit (pdf instructions). I used the Ucup seals instead but same steps to do it.
To be honest, Front lock Cylinder, and the 2 Main Lift Cylinders, were a piece of cake to do. Instructions are pretty easy to follow up, and you can also watch the procedure on youtube, as this example, IMO one of the best explained on youtube.
I drilled the holes (as per pdf instructions) instead of doing a U channel/groove on the cylinder body as our youtuber friend. It is pretty straight forward if you have the proper tooling.
But the fun part comes when it is the turn of the Trunk Lid Cylinders... Those are tricky since the body is steel instead of aluminum
It took me 2 months to figure out how to open these cylinder without damaging them in the process, until I found this humble youtuber's video.
Audio is in spanish, but you know, an image is 1000 words worth. I had to watch the video several times
Eye opener for me. Here some pics of my job.
![Fender Wood Bicycle fork Plumbing Gas]()
Drilled the holes on the cramped marks to release the retainer. Careful how deep you go with the drill bit.
Then tapped the thread for the retainer bolts
![Photograph Tire Bicycle tire White Bicycle handlebar]()
Installed the ucup seal using x-ray film or plastic bottle strips to avoid damaging the seal's lips
![Automotive tire Motor vehicle Wood Gas Automotive wheel system]()
Placed back the cylinder seal retainer 'till it seats flush
![Automotive tire Bicycle tire Wood Gas Bicycle part]()
Now secure the retainer with internal hex headless screws. I think I used 4 or 5mm (M4 or M5), and added a drop of loctite threadlocker just in case.
No need to tighten to death like an engine block. Just hand tight is good enough as this is just a retainer.
I did this repair job like 6 months ago. So far, so good.
But there is always a but... My vario roof sometimes had some hard time opening the trunk lid, so I was thinking it was related to my cylinders service job.
But no... That was not it... 😁
The guilty one this time, was a tiny Tiny TINY O-ring that goes on the pressure relief valve (brass bolt) on the side of the hydraulic pump.
![Motor vehicle Automotive tire Gas Engineering Automotive exterior]()
![Circuit component Electronic device Audio equipment Wire Passive circuit component]()
Stole these pics... sorry about that
There are several posts in this forum addressing this issue. Look for "vario roof relief valve"
Anyways. If you replace your vario roof cylinder seals, it is very likely that this valve O-ring is also rotten, so you will not have the required pressure for the vario roof system to work as expected.
Just my little 2 cents for this forum, that have helped me a lot with my car.
Cheers
At least it was in my case, so I wish that this article become useful to every DIYer who cannot send their cylinders to TopHydraulics or other service shop, or not willing to pay top money for new cylinders. In fact, I do not recommend to buy second hand cylinders as direct replacement, 'cause they will likely fail due to age of seals.
Fact is that oil seals and o-rings age by time and when working with hydraulic oil. Due to system pressure build up, the oil temperature goes up (physics laws), therefore there is a slow cooking of all the rubber involved and within the system.
Nothing can be done to prevent this, but replacing the seals. Luckly MB used nylon hoses instead of regular rubber hoses, so no problem expected there.
So as many users, we have bought the famous kits sold on ebay. Some are O-ring kits, some others use U cup Seals (with lips), which are way better IMO.
Here have attached the instructions that came in with the O-rings repair kit (pdf instructions). I used the Ucup seals instead but same steps to do it.
To be honest, Front lock Cylinder, and the 2 Main Lift Cylinders, were a piece of cake to do. Instructions are pretty easy to follow up, and you can also watch the procedure on youtube, as this example, IMO one of the best explained on youtube.
I drilled the holes (as per pdf instructions) instead of doing a U channel/groove on the cylinder body as our youtuber friend. It is pretty straight forward if you have the proper tooling.
But the fun part comes when it is the turn of the Trunk Lid Cylinders... Those are tricky since the body is steel instead of aluminum
It took me 2 months to figure out how to open these cylinder without damaging them in the process, until I found this humble youtuber's video.
Audio is in spanish, but you know, an image is 1000 words worth. I had to watch the video several times
Eye opener for me. Here some pics of my job.
Drilled the holes on the cramped marks to release the retainer. Careful how deep you go with the drill bit.
Then tapped the thread for the retainer bolts
Installed the ucup seal using x-ray film or plastic bottle strips to avoid damaging the seal's lips
Placed back the cylinder seal retainer 'till it seats flush
Now secure the retainer with internal hex headless screws. I think I used 4 or 5mm (M4 or M5), and added a drop of loctite threadlocker just in case.
No need to tighten to death like an engine block. Just hand tight is good enough as this is just a retainer.
I did this repair job like 6 months ago. So far, so good.
But there is always a but... My vario roof sometimes had some hard time opening the trunk lid, so I was thinking it was related to my cylinders service job.
But no... That was not it... 😁
The guilty one this time, was a tiny Tiny TINY O-ring that goes on the pressure relief valve (brass bolt) on the side of the hydraulic pump.
Stole these pics... sorry about that
There are several posts in this forum addressing this issue. Look for "vario roof relief valve"
Anyways. If you replace your vario roof cylinder seals, it is very likely that this valve O-ring is also rotten, so you will not have the required pressure for the vario roof system to work as expected.
Just my little 2 cents for this forum, that have helped me a lot with my car.
Cheers
