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SL/R230: Convertible Top Hydraulic Fluid Leak Question

     
Old Sep 4, 2025 | 08:59 PM
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Convertible Top Hydraulic Fluid Leak Question
Hello. I ran into an issue today and I'm hoping someone here might be able to help. I have a 2003 SL55 that I've had since 2008. In all that time the top has worked flawlessly with no issues whatsoever (which has always shocked me to be totally honest). Well today the other shoe finally dropped. I put the top down this morning and everything went normal as usual, but when I went to put it up this evening it was moving really slow and actually stopped when it was about halfway up. I waited a couple of minutes and tried again and finally it completed the process but when I checked the hydraulic fluid tank in the trunk it was almost empty and there was a big puddle of fluid on my driveway. There are no visible signs of leaking anywhere on the interior and there is no smell of fluid inside the car either. Any ideas as to what has caused the huge fluid leak onto the ground and what the fix might possibly be? Thanks in advance for any help you can provide.
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Old Sep 4, 2025 | 09:16 PM
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It is usually a hydraulic roof cylinder. I would look beneath your spare tire. If fluid is on the floor of the trunk and leaks out through the drain hole, it is probably the trunk lid lift cylinder or one of the 2 frame lock cylinders. You can touch a frame lock cylinder through a hole in the side trunk liner where the fop's frame is bolted on. If your finger gets wet, that is your leaking cylinder.
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Old Sep 4, 2025 | 10:31 PM
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Originally Posted by aegea
It is usually a hydraulic roof cylinder. I would look beneath your spare tire. If fluid is on the floor of the trunk and leaks out through the drain hole, it is probably the trunk lid lift cylinder or one of the 2 frame lock cylinders. You can touch a frame lock cylinder through a hole in the side trunk liner where the fop's frame is bolted on. If your finger gets wet, that is your leaking cylinder.
Thank you for responding. Yes, there was definitely some fluid on the floor of the trunk and the bulk of it must have leaked out through that drain hole. Since I've never had any issues with the top before could you tell me what's required to do the fix on this and if there's a good place to get the necessary parts? I have an independent mechanic that does all the work on this car and I trust him more than anyone at my local Mercedes dealer so I just have to figure out what parts I'd need to get for him. Thanks again!
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Old Sep 4, 2025 | 10:57 PM
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see: R230 Diagram Top Hydraulics does rebuilds by replacing cylinder o-rings with better quality u-cups. Place an order and pay for core too, return core for partial refund. Cabriolet Hydraulics does rebuilds and can supply line couplers. So you snip the line/hose and don't have to pull the entire hose out. These 3 lines are in the trunk, and easy to re-route to the pump... no need to use couplers.
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Old Sep 4, 2025 | 11:14 PM
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Originally Posted by aegea
see: R230 Diagram Top Hydraulics does rebuilds by replacing cylinder o-rings with better quality u-cups. Place an order and pay for core too, return core for partial refund. Cabriolet Hydraulics does rebuilds and can supply line couplers. So you snip the line/hose and don't have to pull the entire hose out. These 3 lines are in the trunk, and easy to re-route to the pump... no need to use couplers.
Thank you again. It's too late to go out to the garage now but I'm going to investigate further tomorrow and if I feel the frame lock cylinders and neither of them is wet it would have to be the trunk lid one, right? Also, just to make sure I'm understanding you correctly assuming it's either the lock or trunk cylinders I wouldn't need the line couplers from Cabriolet Hydraulics, correct?
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Old Sep 5, 2025 | 12:25 AM
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Probably. The pump could leak back there. But I have not heard of the pump leaking. Again, touch and check for fluid on your finger. You need to remove some rear trunk paneling IIRC to touch the trunk drive cylinder. If a frame lock cylinder is leaking, I would replace the pair.
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Old Sep 5, 2025 | 07:41 AM
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Originally Posted by aegea
see: R230 Diagram Top Hydraulics does rebuilds by replacing cylinder o-rings with better quality u-cups. Place an order and pay for core too, return core for partial refund. Cabriolet Hydraulics does rebuilds and can supply line couplers. So you snip the line/hose and don't have to pull the entire hose out. These 3 lines are in the trunk, and easy to re-route to the pump... no need to use couplers.
Instead of 3 lines, I should have said 3 pairs of lines. Also, correct... you don't need couplers for pairs of lines running through the trunk. You must remove some trunk liners, and separator for when top is down (same color and cover material as trunk liners) to remove frame lock cylinders.
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Old Sep 5, 2025 | 05:56 PM
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Originally Posted by aegea
Probably. The pump could leak back there. But I have not heard of the pump leaking. Again, touch and check for fluid on your finger. You need to remove some rear trunk paneling IIRC to touch the trunk drive cylinder. If a frame lock cylinder is leaking, I would replace the pair.
Hey man, just following up. I finally had a chance to check the trunk area of the SL55 this afternoon and both of the frame lock cylinders were totally dry so I'm assuming the issue is not with them. I couldn't locate exactly where the trunk lid drive cylinder is but there was definitely a lot of fluid pooled in that general area of the trunk floor. By process of elimination I'm assuming that has to be the one that's failed unless it's the pump, but you said that you've never heard of it leaking before so most likely it wouldn't be coming from there. Just to clarify, this is the part I would need to replace if it's indeed what is causing the issue, correct?

https://tophydraulics.com/r230-sl-cl...-cylinder.html
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Old Sep 5, 2025 | 09:13 PM
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That's the cylinder. It is at the left rear trunk wall. You can remove some panels back there to get your finger on that cylinder. All the top/roof lines connect to the pump. It is unlikely that a line connection or the pump is leaking. But those lines are in the trunk.
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Old Sep 5, 2025 | 10:49 PM
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Originally Posted by aegea
That's the cylinder. It is at the left rear trunk wall. You can remove some panels back there to get your finger on that cylinder. All the top/roof lines connect to the pump. It is unlikely that a line connection or the pump is leaking. But those lines are in the trunk.
I'm taking it to my mechanic on Monday to let him look back there and see if he can tell that it's leaking. Since there seemed to be a decent amount of fluid pooled in that area as well as the rest of the trunk floor I'm almost positive that has to be the cylinder that's causing the issue, but I'm going to let him look at it just to be sure before I order the new one from Top Hydraulics. I appreciate you helping me locate the source of the issue...especially since I've never had to deal with a problem on the conv. top until now. Thank You!
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Old Sep 6, 2025 | 04:30 PM
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Originally Posted by aegea
That's the cylinder. It is at the left rear trunk wall. You can remove some panels back there to get your finger on that cylinder. All the top/roof lines connect to the pump. It is unlikely that a line connection or the pump is leaking. But those lines are in the trunk.
Just one more quick follow up question for you...any idea how long it takes for a skilled mechanic to swap out the old trunk cylinder for a new one? Thanks again for all of your help.
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Old Sep 6, 2025 | 06:14 PM
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I imagine, if you really know what you are doing with the right tools in hand, a skilled mechanic could swap it out in an hour. Be careful not to break the electrical connector.
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Old Sep 6, 2025 | 06:27 PM
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Originally Posted by aegea
I imagine, if you really know what you are doing with the right tools in hand, a skilled mechanic could swap it out in an hour. Be careful not to break the electrical connector.
OK, thanks. I will definitely mention that to him before he starts on the job. Thank you again for all the advice.
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