Rebuilding Convertible Top Cylinders - Mercedes-Benz Forum
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#1 (permalink) Old 08-15-2009, 10:52 AM
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Rebuilding Convertible Top Cylinders

This is a basic guide for replacing the rod seals in the hydraulic cylinders that operate the SLK convertible hardtop roof. O-rings are used to replace the U-shaped rod seals that fail and cause hydraulic leaks. For detailed instructions on how to remove these cylinders, go to:

SLK Home Page

The small latch cylinder located under the headliner is probably the easiest to do, so let's start there. The first part is removing the bracket. The bracket is the small U-shaped metal piece on the tip of the rod. It has been connected to the rod using a small slide-on sleeve. The sleeve slides over a small groove on the tip of the rod. The sleeve is then pin-punched, holding it to the rod and thus securing the bracket to the rod. There are two ways to remove this sleeve. The small dimple created by the factory pin-punch can be drilled out, or a punch can be used to force the bracket off the rod. I do this by putting the rod portion in a vice. Do not clamp down on the rod or else it will be destroyed. Leave it loose between the jaws so that the bracket is resting on top of the jaws with the exposed rod tip pointing straight up. Use a metal punch and hammer to tap the tip of the rod down through the sleeve. This will shave off the small dimple of metal inside the sleeve holding the sleeve in the rod groove. Remember, the rest of the cylinder is not clamped in the vice, so do not let the cylinder fall on the ground once it is free of the bracket. Now that the bracket is off, put the body of the cylinder in the vice and push the rod all the way into the cylinder. Looking into the cylinder around the rod, you will see a small C-clip holding a white nylon bushing. The bushing can be tapped down into the cylinder about a quarter of an inch. Doing this will give you room to remove the C-clip. Tap the white bushing lightly, working all the way around. Do not deform the bushing. Once the bushing is all the way in, remove the C-clip. This is best done with two small flat screwdrivers or a small hook. Its almost an art and requires patience. Mercedes could have used a snap ring, so that snap ring pliers could be used to remove it, but they didn't. Remember, you are rebuilding cylinders that Mercedes designed to be disposable. Once you have worked your magic and removed the C-clip, the entire rod and piston assembly pulls out of the cylinder. It may be very tight and need to be tapped out. To do this, you could clamp the rod in the vice with wood or cloth around it to protect it, and tap on the end of the cylinder. Or, you could clamp the cylinder in the vice and tap up on the rod by holding the grooved tip with pliers. Either way, it's not that difficult to get the rod and piston out. Once they are out, slide the seal off the rod and replace it with the O-ring. Insert the piston and rod back into the cylinder with the new O-ring. The white nylon bushing will push the O-ring over the C-clip groove in the cylinder. Make sure the white nylon bushing is put on the rod in the right direction. The end with the round edge ends up touching the C-clip. This is designed to help hold the C-clip in and pushes it up against the cylinder wall. If you install the white bushing backwards, there is a possibility that the C-clip may not hold everything in. After sliding in the white bushing, insert the C-clip back into the groove. The bracket now needs to be reconnected to the rod. There are several ways to do this. One, is to use the original sleeve and pin-punch it in a new spot. To do this, slide the bracket back onto the rod and the sleeve slides back over the groove. The sleeve will need to be pin-punched back into the groove. Do not use the original spot, rotate it and use a fresh area. lay the assembly on a hard surface, like a vice, and support the area under the sleeve. Use a hammer and center punch to hit the sleeve and dent it down into the rod groove. Another option is to leave off the sleeve, put on a couple of washers for spacers, and use a snap ring from the hardware store. This can leave the bracket looking a little bit loose, but that should not be a problem. The bracket does not need to be tight to function properly. However, if it is too loose, you may hear an additional small click noise when the cylinder opens and closes. Once again, functionality will not be compromised. An ever easier option, is to use a small nail the same diameter and the groove in the rod. Bend it into a U or oval C shape, and install it with some washers for spacers. The washers will most likely need to be ground down or filed down to fit into the bracket. Once again remember, you are rebuilding a cylinder designed to be disposable. There is no official rebuild kit, no OEM parts available to the public, only the determination of a few to provide people with a low cost solution.

The larger Cylinders are a little bit trickier to disassemble. The first step is removing the bracket. The bracket is the small U-shaped metal piece on the tip of the rod. It has been connected to the rod with threads and can be unscrewed. The best way to do this is to extend the rod all the way out and hold it in a vice. The surface of the rod cannot be marred or scratched in any way. It must be protected using two pieces of flat wood between the vice jaws. I first tried using very thick cloth, but the bracket was on so tight that the rod just spun in the cloth. Once the rod is held tightly in the vice, I inserted a thick round shaft screwdriver into the two round holes of the bracket. I then used a hammer to hit the handle of the screwdriver to loosen the bracket. Make sure to hit it in the counter-clockwise direction. Once the bracket is off the rod, push the rod down into the cylinder as far as it will go. You will see that the threads on the tip of the rod go into the cylinder past an aluminum ring and a fibrous ring. This fibrous ring is called the rod wipe and functions to keep the rod clean and to keep dirt out. It is flexible and not a solid circle, so it can be pulled out with a small hook without removing the aluminum washer. The advantage to doing it this way is that next you can remove the aluminum washer without destroying it. This is done by inserting a small U-shaped washer behind the aluminum ring, screw the bracket back on a little way, then tap the bracket using the round shaft screwdriver and hammer. You will be tapping it in the direction to make the rod come out of the cylinder. This aluminum washer is lightly pressed in and is not difficult to remove. Once the fibrous rod wipe and aluminum ring are removed, push the rod back down into the cylinder. Looking into the cylinder around the rod, you will see a larger C-clip holding a white nylon bushing. The bushing can be tapped down into the cylinder about a quarter of an inch. Doing this will give you room to remove the C-clip. Tap the white bushing lightly, working all the way around. Do not deform the bushing. Once the bushing is all the way in, remove the C-clip. This is best done with two small flat screwdrivers or a small hook. This larger C-clip is more difficult to remove that the smaller C-clip used in the smaller latch cylinder. Remember, its almost an art and requires patience. Once you have worked your magic and removed the C-clip, the entire rod and piston assembly pulls out of the cylinder. It may be very tight and need to be tapped out. To do this, screw the bracket back onto the rod, and use the hammer and round shaft screw driver to tap the rod and piston out. It's not that difficult to get the rod and piston out. Once they are out, slide the seal off the rod and replace it with the O-ring. Insert the piston and rod back into the cylinder with the new O-ring. The white nylon bushing will push the O-ring over the C-clip groove in the cylinder. Make sure the white nylon bushing is put on the rod in the right direction. The end with the round edge ends up touching the C-clip. This is designed to help hold the C-clip in and pushes it up against the cylinder wall. If you install the white bushing backwards, there is a possibility that the C-clip may not hold everything in. After sliding in the white bushing, insert the C-clip back into the groove. Next, tuck the fibrous rod wipe in, and tap in the aluminum ring. The bracket is then screwed back onto the rod. Congratulations! You have done it!!!


I would also like to say "Thank You!!!" to all the dedicated people on this site who helped me with info that lead to this guide, and also to those who helped test them!!

Mark Andrews
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#2 (permalink) Old 10-10-2009, 10:03 PM
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Hi Mark any ideas about the trunk cylinder can that be fixed thanks in advance
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#3 (permalink) Old 12-05-2009, 09:07 AM
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Maybe it will help you guys. I never rebuilt SLK hydraulic cylinders yet, but I did many on SL and W124 convertible models. The seal that fails is a polyurethane U-seal. Standard shape, but not a standard size. I have people in Europe to manufacture the seals for me in small quantities and shipping them to me about once a month. The seals are made of polyurethane and are the exact replacement of the original. Hopefully, they will last longer though. I sell the kits for SL and W124 cabrio owners all the time. If one of my sizes fits SLK - great. If not, I need to know the size and my guys can TRY to manufacture it. They have equipment used for military production and even than struggled to make some small cross-section seals. Took many attempts, but succeeded. So, there is no promise, but worth a shot. email me if interested tmmatr102@sneakemail.com.
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#4 (permalink) Old 12-08-2009, 05:57 PM
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thanks dear for the offer but I have already built it and have posted a DIY for it . you can find seals at rocket seals.
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#5 (permalink) Old 12-09-2009, 08:52 AM
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Originally Posted by rimba View Post
thanks dear for the offer but I have already built it and have posted a DIY for it . you can find seals at rocket seals.
You are lucky! No seals for R129 though. They all have non-standard size.
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#6 (permalink) Old 12-21-2010, 10:30 PM
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Yes. What about trunk cylinders? How to disassemble those?

Attack life! It's going to kill you anyway.
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#7 (permalink) Old 12-22-2010, 02:29 PM
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Post rebuilding trunk cylinders

The trunk cylinders are harder to disassemble and put back together than the others. We use industrial presses for the re-assembly.

Top Hydraulics is rebuilding ALL Mercedes hydraulic top cylinders. That includes R129, R230, R170, R171, W208, W209 -- they all fail in time! We are actually rebuilding Porsche and BMW cylinders, as well.

All of these OEM cylinders use Polyurethane ('PU') cup seals. We have developed special seals that have all the desired characteristics of the original PU cup seals that MB uses, but we use enhanced Polyurethane with a PTFE back-shell. (PTFE is the chemical term for Teflon, which is trademarked by DuPont). That way, you should not have to worry about needing to rebuild your cylinders again, as long as you own the car.

We do not use standard PU seals, and certainly not O-rings. O-rings are big time wrong for this application; they are meant to seal non-moving surfaces.

We usually turn around the rebuilds within a day, plus Priority Mail shipping to most locations inside the US taking two days. Three years warranty.

Cost is currently $55/cylinder plus flat $10 shipping fee per order in the US. If you damage only one cylinder in your whole set while trying to fix it yourself, you'll probably end up paying more than we charge to rebuild all five cylinders...

www.topcylinders.com

Hope this helps,

-Klaus

Klaus Witte, Top Hydraulics, Inc.

We upgrade and rebuild hydraulic cylinders for Mercedes R129, R170, R171, R230, W124, W208, W209,
as well as Audi, Bentley, BMW, Cadillac, Chrysler, Ferrari, Infiniti, Jaguar, Lamborghini, Lexus, Mini Cooper, Opel, Peugeot, Porsche, Rolls-Royce, Saab, VW


Also rebuilding pumps and ADS valves...

www.tophydraulicsinc.com

Convertible top hydraulic system diagrams and DIY instructions:

http://www.tophydraulicsinc.com/en/c...y-instructions

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#8 (permalink) Old 02-25-2011, 11:12 AM
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great write up but tricky without pictures. That is unless you actually read it whilst doing the job - I prefer to read first act later....
are there any pic type guides around what mark has done?
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#9 (permalink) Old 02-25-2011, 01:20 PM
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Quote:
Originally Posted by KBelov View Post
Maybe it will help you guys. I never rebuilt SLK hydraulic cylinders yet, but I did many on SL and W124 convertible models. The seal that fails is a polyurethane U-seal. Standard shape, but not a standard size. I have people in Europe to manufacture the seals for me in small quantities and shipping them to me about once a month. The seals are made of polyurethane and are the exact replacement of the original. Hopefully, they will last longer though. I sell the kits for SL and W124 cabrio owners all the time. If one of my sizes fits SLK - great. If not, I need to know the size and my guys can TRY to manufacture it. They have equipment used for military production and even than struggled to make some small cross-section seals. Took many attempts, but succeeded. So, there is no promise, but worth a shot. email me if interested tmmatr102@sneakemail.com.
I got a dedicated email since this post. It is mbcylinders@gmail.com So, discard the old one, it does not work. There are some pictures of the cylinder rebuilding for W124 cabrio and R129 at Mercedes-Benz Convertible top hydraulic seals. Maybe it will help just to give you a general idea. The process is not difficult at all. You do not have to machine the cylinders to accept the standard seals like many rebuilders do. Just pop a new seal in. If you can get the cylinder out of the car, you can rebuild it.
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#10 (permalink) Old 02-25-2011, 02:14 PM
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Rebuilding and upgrading R170 cylinders

Kbelov, thank you for the link to your website that talks about R129 seals. Unfortunately, the rebuilding process for R170 cylinders is a bit more complicated. Also, none of your sizes fit the R170 cylinders.

Top Hydraulics now sells custom cup seals for all R170 cylinders at $25 per piece. (I think you are charging $30/ea. for R129 seals? It didn't take any trying to make them right; our software creates the perfect cup seal for the application right away. We rebuild and upgrade ALL Mercedes top cylinders, plus Porsche and BMW. What's more, when we rebuild the cylinders that are being sent in to us for upgrade, we use our proprietary hybrid seals with a Teflon back-shell for even longer life. We do not sell the hybrid seals.

On the roof latch cylinder, the part that connects the cylinder to the latch mechanism is pressed on at the factory. It needs to be drilled out or punched off. Marty's ('Shockwave Technologies') instructions admit that the part will be loose and may rattle when you reconnect it with something like a snap ring. Top Hydraulics provides a firm, industrial re-connection.

On the trunk cylinders, there is some precision machining required, as well as re-assembly with a hydraulic press or similar means. I would highly recommend to send these cylinders in to Top Hydraulics, since we have the industrial tools set up to do the job right. In those instructions that are for sale on eBay, it says more or less that they are 'extremely difficult if not impossible to fix'. I want to be careful with the language here, because Marty Ewer says he has copyrighted the material, and I have had my encounters with him that ended up in very 'unusual' monologues from his side. I don't want to expose BenzWorld to more of that. There are also claims that these cylinders rarely fail. Wrong - we get about an even mix of the various SLK cylinders in for rebuild/upgrade.

On the lift cylinders, it is still harder to do the job yourself than on the R129 cylinders, but you can get there with persistence. The main concern is that these cylinders are very expensive to replace, and that is exactly what you'll have to do when you scratch the piston rod. I have had plenty of R170 owners send in their cylinders for repair after they tried it themselves and scratched them up...

We'll update our website shortly to include a "Buy Now' button for the R170 seals. Meanwhile, anyone can send payment to PayPal account tophydraulics@aol.com. Shipping would be $2 for regular mail, $5 for domestic Priority Mail, or $15 for International Priority Mail. Just add to the payment instructions which cylinders you need the seals for.

Currently, we charge $55 per rebuild/upgrade on R170 cylinders, plus flat $10 Priority Mail shipping in the US.

Klaus Witte, Top Hydraulics, Inc.

We upgrade and rebuild hydraulic cylinders for Mercedes R129, R170, R171, R230, W124, W208, W209,
as well as Audi, Bentley, BMW, Cadillac, Chrysler, Ferrari, Infiniti, Jaguar, Lamborghini, Lexus, Mini Cooper, Opel, Peugeot, Porsche, Rolls-Royce, Saab, VW


Also rebuilding pumps and ADS valves...

www.tophydraulicsinc.com

Convertible top hydraulic system diagrams and DIY instructions:

http://www.tophydraulicsinc.com/en/c...y-instructions

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