[Cool R230]

Well for us here in Florida the winter is over. The temperature is above 50°F and the sun is shining, it's convertible weather! I have had my car for a little over a year now and unless it's raining or parked, the top is down! In all fairness to the rebuilders of top cylinders that are here on the forum, my saga started immediately after purchasing the car and well before I really discovered this place. I bought the car as a project all of the common ailments that you could find on a neglected 04 R230 - Dead consumer battery, ABC issues, inoperative Vario roof, frozen PSE (vacuum) pump, etc. The car had not been driven in 2 years prior to my purchase and the systems had just fallen into disrepair. Once the car was running and driving without red warnings on the dash, my highest priority was to go topless! The first warning that something was awry was the dripping hydraulic oil from the headliner on the passenger side of the car.
If you are reading this, you probably already know what the problem was...the front lock cylinder was leaking fluid at an alarming rate! So, in may standard approach to mechanical things....I took it apart! What I found was a nicely manufactured cylinder....with a seal that nobody locally could seem to match! The seal is a small metric seal 16mm O.D. x 9mm I.D. x 4.5mm tall. I was rather stuck. I was able to disassemble the cylinder without removing it from the car or disconnecting the hoses, only to discover that a suitable repair part was not readily available.... or was it?
I pulled out my calculator and determined that 16mm = 0.630" only 0.005" larger than 5/8", and 9mm = 0.354" ...0.021" smaller than 3/8" so I want to the local hydraulic shop and asked for a 5/8"O.D. x 3/8"O.D. x 1/8" seal.
I knew it was real close on the O.D. but was a little dubious on the bore size...after all there was 0.021" plus 0.005" to make up....imagine my surprise and delight when the the system pressured up, the top came down and my love for this machine was confirmed!
Now If you're still reading this and think that that was the end of the story...it's not. The inch size seal that I installed served me for nearly a year...but it dripped..maybe a drop a day. Clearly this was not a permanent fix, i had not replaced the headliner because I would need to wipe off that dangling drop of oil occasionally... It was a pain that was instantly cured by dropping the top, but something had to be done!

 

[Cool R230]

Vario Front lock hydraulic cylinder fixed, Continued.

Now, the owners of SLKs seem to be doing repairs on what look like the same type of cylinder by replacing the offending seals with an O-ring that is stretched over the piston. They seem to be satisfied with the results but I was again somewhat dubious of an O-ring in that application. I finally tired of the bare ceiling looking like the interior of a WWII era airplane and decided to fix this thing once and for the next 8 years (just a hunch that the Florida sun will cook this seal in that time frame)!
After a relentless search (after all we have the internet now) I was able to source a seal to do the job. I ended up with a 16mm x 9mm x 4mm urethane seal that fills the bill perfectly. I have attached a photo of the L-R new replacement seal, the original seal that has lost the inner lip, and the inch size seal that has been allowing me to breath for the last year!

 

[Cool R230]

Vario Front Lock hydraulic cylinder fixed, more.

There is just one last detail that I thought was worth sharing. The clevis on the end of the piston rod is held in place with a plain collar that is deformed in a press to clinch it in place. I was able to drill out the detents to relieve the pressure and drive the collar and clevis off the rod. This was necessary to replace the seal....but (Insert usual disclaimer) I am a trained professional ... etc, etc,... If you are not sure that you can perform this, or any other repair without doing damage to the expensive, delicate things, you may want to leave this to the professionals. There are shops that perform excellent service at a reasonable cost that both support and provide excellent information to everyone and that may be found on this very forum. :smile

As for myself, I just love to take things apart, put them together and watch them work.

I got carried away... what I wanted to say was that I replaced the plain collar with a 1/4" wheel collar from the hobby shop. I had to flatten the sides with a few strokes of a file and replace the short setscrew with an allen head cap screw that I had ground to a point (to engage in the slot on the rod). Because I opted for a cap screw, tho orientation is important to clear the lock mechanism when the cylinder strokes.
Now it's buttoned back up...and working like new. :wink

 

[SinSL]

I hope your fix holds, but other people failed to address the issue with a seal swap. From brand new, these cylinders last only 8-10 years, then start going pretty much at the same time. I used TopHydralics (Top Hydraulics | Rebuilt and Upgraded Convertible Top Cylinders, Pumps, Hydraulic Lines - Top Hydraulics, Inc) to rebuild them, and these rebuilds considered better than OEM new part.

 

[TopHydraulics]

About fixing cylinders yourself

Cool R230,

congratulations on fixing the external leak on your cylinder. You are obviously good with your hands, because MOST folks would have damaged the chromed shaft of the cylinder when taking it apart. We get in damaged cylinders from failed DIY repair attempts every day.

A couple of comments, without trying to take away your triumph:
1) Off-the-shelf seals like the one you bought are even worse in quality than what Mercedes' supplier put in originally. Thus, you can count on a shorter service life than the first time around.
2) It is important to change the piston seals on these cylinders. If there is an internal bypass on the piston seal of p/n A 2308000872 (top lock cylinder) or p/n A 2308000972 (left trunk frame lock cylinder) or p/n A 2308001072 (right trunk frame lock cylinder), then your top will mysteriously move slower. See http://www.benzworld.org/forums/r230-sl-class/2160793-vario-roof-failures-repair.html.

As SinSL kindly pointed out, Top Hydraulics truly makes all Vario roof hydraulic cylinders better than brand new, because our seals will far outlast the OEM seals. See location diagram below.

Keep an eye on the remaining ten cylinders - a failing 230 800 08 72 is just the beginning.

Klaus

Top Hydraulics, Inc
www.tophydraulicsinc.com
http://www.tophydraulicsinc.com/en/21-r230-sl

 

[kev1900]

I think I will

I think I will have Top Hydraulics fix mine for $65. To me that is a bargain!

 

[Cool R230]

Questions

Another Floridian was asking some questions regarding removing the retaining clip in the aluminum body cylinders. There have been some threads that suggest drilling a hole in the body of the cylinder at the clip groove in order to help removing the clip. I did that for the first one and it worked OK, but I decided that there had to be a better way. I made a tiny hook out of music wire that allows me to hook the end of the clip and pull it directly out. Before anyone gets too excited, please be aware that i install a plastic sleeve over the shaft to protect it from scratches. Attached are some photos of the tool next to a small pocket screwdriver to give you a feel for the scale.

 

[jetkit]

Where?

Now, the owners of SLKs seem to be doing repairs on what look like the same type of cylinder by replacing the offending seals with an O-ring that is stretched over the piston. They seem to be satisfied with the results but I was again somewhat dubious of an O-ring in that application. I finally tired of the bare ceiling looking like the interior of a WWII era airplane and decided to fix this thing once and for the next 8 years (just a hunch that the Florida sun will cook this seal in that time frame)!
After a relentless search (after all we have the internet now) I was able to source a seal to do the job. I ended up with a 16mm x 9mm x 4mm urethane seal that fills the bill perfectly. I have attached a photo of the L-R new replacement seal, the original seal that has lost the inner lip, and the inch size seal that has been allowing me to breath for the last year!

CoolR230, where can I buy this seal?

 

[Cool R230]

And now the rest of the cylinders

I’ve found myself with some down-time, being in a hotel room thousands of miles away from my car and nothing to do. I thought I would log the rebuild of the rest of the cylinders. Mostly for my own purpose but so that others may benefit as well.

As I said in my text, I logged this information mostly for my own benefit but maybe there are a few others that may find it interesting.

And good luck YMMV. :nerd

It was only a matter of time until the next in line sprung a leak, the trunk (boot) lock cylinders were next.
Emboldened by what I learned during my first rebuild, I attacked these in much the same fashion. Using the tools I made to extract the wire C-clip from the bore of the cylinder, I was able to remove the piston assembly without disturbing any of the hydraulic lines.

I simply detached both ends of the cylinder from the lock mechanism and using the protection sleeve and the tiny clip hook, pushed the white plastic retaining plug down into the cylinder, hooked the end of the C-clip and pulled it out. I did not need to drill a hole in the cylinder using this technique, the tools do the job nicely. The piston assembly pulls straight out of the cylinder ready for the next step.

 

[Cool R230]

To replace the 9mm x 16mm lock cylinder seal, the clevis (rod end) must come off. The people who manufacture these were deliberate in creating an easy to assemble and reliable connection….provided you never needed to take it apart. The rod end is machined from mild steel and there is an indention on both sided of it where a press was used to upset (deform) the material to lock into grooves machined in the piston rod. After much googling (including in german), inspection and thought, I determined that shallow drilling would be the way to go. I didn’t want to get too far into the shaft with the drill but I did need to weaken the material around the upset to be able to get the thing apart.


I decided to attack it in a 2-step approach, if I recall correctly these are ¼” (6.4mm) drill bits. I reground the one in the foreground to remove the point. It is basically ground to resemble a 2 flute end mill, to drill a flat bottom hole. I started the hole with the regular bit then switched to the other one to remove the metal near the upset without the point getting too far onto the rod.

Once I had removed as much material as I dared, I turned the shaft vertical and drove the rod out of the clevis through the hole in the that is in the clevis that is on the on the rod centerline. Naturally the protective sleeve had been in place during all of these operations.


With the clevis removed, we can replace the seal and prepare to but this thing back together.

Reassembly – Having removed the material at the upsets, there was nothing to deform to lock the clevis to the rod as it was originally manufactured. Of course I hated the way it had been manufactured so I opted for an alternative. The rod is fully engaged in the clevis, that is to say that the rod is bottomed out in the hole that receives it. The hydraulic cylinder has a different value on the force that it generated when it is extending and retracting given the same supply pressure.
In doing research I found a great site by a guy that seems to have taken everything apart on his car and really gets into detail.
From the internet: OLDTIMER: Tipps für Mercedes SL55AMG
This says that the hydraulic unit can produce 210 bar pressure, that’s a little over 3000 psi to those speaking that lingo.
I do a little math and find that I need a plan to keep the clevis on the rod end when it’s pulling at as much as 170 Kilograms Force, or 374 Lbs.
I decided on 3/32” diameter roll pins, the double shear rating is 1150 Lbs. so I have a 3x safety factor, sold!


Back together.

 

[Cool R230]

Trunk Cylinder Rebuild

Trunk Cylinder
If you’ve followed along so far, you will recognize that as each cylinder springs a leak in this car, the level of complexity for the repair increases. I recognize that this is not for 99.a lot% of the people who may read this. The SLK owners that are repairing their cylinders may recognize some of the challenges in rebuilding the cylinders that are pressed together….but the SL is different.
Here is the trunk cylinder.




From the photos, we know that we must:
1. Drill out the dimples that retain the seal retaining plug where the rod exits the cylinder.
2. Somehow extract the plug that retains the seal.
3. Drill the upsets out where the clevis is connected to the rod.
4. Drill a hole through the clevis that is coaxial to the rod centerline so that we can drive the rod out of the clevis.
5. Replace the seal.
6. Figure out a wat to hold everything together once its reassembled.
The more of these you do, the more the order of operations matters. Let’s get started


Drill out the dimples I decided on a 11/64” drill bit as this is the size for an 12-24 tapped hole. I intend to use 12-24 setscrews in shear to hold the seal retaining plug.


Here I have grabbed the cylinder in a workmate, As the cylinder is soft carbon steel it seems like a bad idea to hold it in a regular vice. If you squeeze too much you’ll destroy the cylinder. The SLK owners that replace the seals in their cars are familiar with this operation. I don’t know if the tolerances are different on the SLK to the SL but I was unable to get the plug out as it has been described by others. We need a plan….Later


Once the plug and seal are out (Magic) the clevis must come off, This was shown in the Trunk Lock cylinders but there is more work that must be done here as there is no existing hole to drive out the rod from the clevis. It’s important to protect the surface of the rod at all times. I made sleeves out of various pieces of tubing for protection during operations. Remember to check the interior of the sleeve for material before installation to prevent foreign material from scratching the surface of the rod.

 

[Cool R230]

Drilling the coaxial hole. This is actually a roof cylinder, I didn’t think to snap one when I was doing the trunk cylinder, same, same

Holes tapped and ready to be closed up. I had to grind some length off the setscrews for the trunk cylinder to get them to be flush with the outside of the cylinder. There is a plastic sleeve on the position switch that must slide over the cylinder and any retaining devices must not project above the OD of the cylinder.


Done… except for the clevis and that is retained as described on the trunk lock cylinder.

 

[Cool R230]

Cylinder Disassembly – Seal retaining plug removal.

Cylinder Disassembly – Seal retaining plug removal.
This my solution to extracting the old seal and retaining plug. I rationalized that internal pressure would be the answer, the problem was getting the pressure in the cylinder to do the work. It needed to be something that had some power behind it and could be controlled. I had a hydraulic pump for a porta-power that I thought would do the job but the connections on the tubing are a rare sample connection that I was unable to find fittings to match.

Cylinder disassembly Photos 007 - 010: This fitting started life as a brass compression fitting, I think it was a 3/16” tube x ¼” NPT. There is an O-ring that that sits down in the bottom of the socket that you see in the top of the fitting. This fitting is sealed around the perimeter of the nipple that is below the bulb on the tube, not against the bulb. The O-ring is trapped in the bottom of the pocket and we must hold the tube in the pocket somehow.

I made a split collar to be inserted above the bulb in the tube end.

Run the nut down over the split collar finger tight everything is sealed up and ready to go.

The cylinder must be held partially extended to allow room for the seal and plug to slide out of the cylinder.

Set-up and ready to push

Need to cover it with a rag for when the plug pops out the end of the cylinder. That’s it, no pounding no punch, success!

 

[Cool R230]

Finally!

 

[Cool R230]

Lift Cylinder -Rebuild

Lift Cylinder -Rebuild

OK so I deviated from my previous plan, I decided to use an end mill to remove the material at the upset, I did this in the drill press, if you go this route make sure the vice is securely bolted down as there is no center to keep things steady.

Just enough material removed to expose a bit of the rod.

Driving the rod out of the clevis.

The lift cylinder must have both ends removed to replace the piston seal. This cylinder is different from the others in that it is a single acting cylinder. The piston seal is a U-cup just like the rod seals that we have been replacing….so it needs to be completely blown apart to this level. Now there is also a design flaw that I think should be addressed. The bottom of the cylinder is sealed with an O-ring and I think this is an issue waiting to happen.

If you consider how this unit operates, the hydraulic pressure retracts the piston and the roof assembly extends it. If you have any leakage past the piston seal, fluid will collect in the space between the piston seal and the dead end of the cylinder. If you are unlucky enough for this to happen, the stroke of the cylinder will be reduced by the volume of fluid in this dead end. Eventually there will not be enough stroke for the roof to operate and yet there will be no leaks, May be a tough one to diagnose. I reassembled my lift cylinders without the O-ring, YMMV.

 

[Cool R230]

Roof Operation cylinder

Roof Operation cylinders
If you’ve followed along, the roof operation cylinders require all of the same operations as the others. They are the largest of the pressed together cylinders and do see greater forced. You will notice the clevis has 2 upsets rather than 1 as seen on the other cylinders. I installed a pair of roll pins to hold the clevis on the rod in these units.

 

[Cool R230]

Roll bar cylinders and follow-up thoughts

Roll bar cylinders


Roll bar Pawl Cylinders
Tiny things, Held together with a C-clip, Can’t seem to find seals this small. 5mm x 8mm

Some follow-up thoughts from the rebuild:
There is a reason that the rebuilders of these cylinders get the money they do for their work, they earn it. This is not a job for the average home gamer unless you have the tools, know-how and motivation, rebuilding these units is best left to the professionals.
On the dimpled cylinders, the plugs that retain the seals are really tight in the bore of the cylinders. I opted to take a couple of thousandths off of them in the lathe so that they would slide down into the bore more readily. I anticipate that when these begin to leak I will be able to replace them with much less trouble.
If you are going to use threaded fasteners to retain the plugs, the 12-24 x 3/16” setscrews worked alright but the 0.174” holes were just a bit on the small side to catch all of the dimple. I was left with some burrs that needed to be taken off the bore of the cylinder. A ¼-28 may have been a better option due to the larger drill size. I was concerned about the edge distance with a larger hole there is less material between the edge of the hole and the end of the cylinder. I also may have opted for 1/8” long as all of the fasteners could have been set flush with the outside of the cylinder making it look nicer (small detail)
Mark the plug to maintain the orientation. I put a punch mark to match the inlet port orientation. This will be handy to get the threaded holes to align when you take these apart.

Hope this may be of help to someone out there...

 

[ichris's_dad56]

Outstanding write up and documentation. It is so easy to find instructions on rebuilding the SLK cylinders, but this is the first I've seen beyond the locking cylinder on the R230.

Tim

 

[Heatwave]

Excellent write-up. Many thanks for your thoughtfulness and diligence in making the pix and posting on the forum. If it all teaches me anything ... and it clearly does ... this project is over my paygrade.

 

[JettaRed]

You have just convinced me to go with TopHydraulics when the time comes. Great write up! But I'm in the 99% that wouldn't try the rebuild.