So, I was closing the top yesterday and everything went fine until I suddenly heard a sound of liquid leaking, like an elephant... anyway, the roof stopped and the pump was sucking air. I closed the top manually (thanks to the instructions in this forum, memorize them people, memorize them) and took a better look at the problem today.

The hydraulic fluid was way below minimum and the floor around the pump was swimming in the fluid. I bought some Febi/Bilstein and filled the tank. I cycled the roof once, I mean opened and closed it. No problem at all, but I could hear that the liquid was leaking out again. Opened the rear part manually and the "firewall" between the roof hole or whatever you call it and the rear seats was dripping hydraulic fluid. In one open-close cycle the liquid level went from max level to below minimum. It looks like that the case cover lock is leaking.

My question Nº1 is: Can one cylinder really leak that much or is there something else in that area that I'm missing? I tried to validate the theory by putting some paper towels around the case cover and tried to open the top and the paper was soaked in fluid.

Q Nº2: Is the whole system like a serial system? I mean the fluid leaks out also if I move the roll bars, can it still be the case lock or are the roll bars a separate system?

Thanks in advance

 

The seals MB used in the power roof/RB system's 8 hydraulic cylinders have a service life of about 10 years. By far, the 2 cylinders that leak the most frequently, are the rear bow and case cover units. Note: As a long time forum member and original owner of a 2001 cabriolet, knock on wood, going on 16 years, my power roof has worked faultlessly, with the earlier failures seeming to be occur in warmer climates.

When the hydraulic pump is operated, it generates about 150 bars of pressure. Note: 1 bar is atmospheric pressure at sea level. In terms of pounds per square inch (i.e. psi), 150 bars is 2175 psi of force.

From your description, it is still very possible that you have a case cover lock cylinder seal failure.

Although less common, I would also check for a hydraulic line failure as well (e.g. rupture, connection etc.). Note: The fittings are retained to the cylinder with locking clips. See the section on case cover locking cylinder at:

https://www.tophydraulicsinc.com/en/...y-instructions

You can check for the leak source by having someone momentarily operate the pump and visual inspection. However, be very careful when doing this, as to not get hydraulic fluid in your eyes etc..

Lastly, in terms of hydraulics, the power roof and roll-bar are separate. Integrated on the pump assembly is value block with 7 hydraulic lines or branches, that operate the power roof hydraulic cylinders. The roll-bar assembly has it's own separate value block, hydraulic lines and an8th cylinder to raise/lower the bar.

The control module analyzes the positions of the various limit and operating switches and correspondingly switches the solenoid valves incorporated within each value block, to actuate the required hydraulic cylinders.

So while each of the 8 hydraulic cylinders are on a separate branches (e.g. not configured serially), I suspect that operating the roll-bar, which turns on the pump to provide full pressure, also provides higher standby system pressure, to cause a major leak to continue.

I've included a diagram of the power roof/roll-bar system that might help in following the above explanation.

The good news, is that, if you're wrench handy, most failures have already occurred, there are still some forum members to help with DIY repairs and a forum sponsor, Top Hydraulics, to help get your power roof system back into as new working order, at modest expense.

 

Hello Raindance,

allow me to add some comments below in addition to Serndipity's detailed response. Serndipity is a lucky guy that his top system has not leaked yet. In any case, we all owe him a lot of thanks for all the trouble he is going through to answer forum members' questions very precisely.

If you put paper towels around the case cover lock p/n 1247500684 (model years '98-'00) or p/n 2087500984 (model years late-'00 through '03) and the towel got soaked, then you are almost certainly looking at a significant leak from the cylinder p/n 1298000072 inside the lock. To answer your question: YES, one cylinder can really leak that much. Looks like the leak is in an advanced stage.

YES, in cases of total seal failure, the locking cylinders can leak even if only the roll bar is moved.

By far the most commonly used solution in cases like yours is Top Hydraulics' core exchange option for rear bow lock and case cover lock already mounted in matching locks. It'll cost you $160 plus $300 refundable deposit plus shipping. There is even a write-up about it in the upcoming STAR magazine (magazine distributed to members of the MBCA - Mercedes Benz Club of America)...

Model years '98-'00: https://www.tophydraulicsinc.com/en/...-assembly.html

Model years '01-'03 (including late '00 models): https://www.tophydraulicsinc.com/en/...-assembly.html

-Klaus



Location of the A208/W208 CLK cabriolet hydraulics

 

Thanks everybody for your replies. I'll still check the leak again with somebody activating the pump while I look for leaks but it seems that the case cover cylinder is the problem.

Klaus, I'll be in touch for repairs...

DIY hint: when working on the pump, putting a bungee cord from the roof lock latch over the roof to the windshield wiper helps a lot as you don't need to worry about the back of the roof falling on your head. I'll attach a photo later when I'm on the computer.

 

Serndipity and Klaus helped me immensely get my issues resolved. I had both the bow and case lock cylinders leaking, then had a failed roll bar limit switch on top of that. I had around $300 in parts (including a trip to MB dealer to have codes read) to get mine back working - and of course the fantastic help from the folks above. The dealer quoted me $7k for just the roll bar switch...

 

Wrenchworkwise it's not that difficult to get to the pump and the cylinders once you know where they are and how to get to them, and that is exactly where all the unpaid help from Serndipity and Klaus as well as everybody else in the forum comes into the picture. Very much appreciated.

JG403, I had an aircon issue with another car I had and the dealer's idea was to change the compressor at around 1300 Eur to see IF that was the problem. Thanks to some forum folks, it turned out that all it needed was 3 hours of work and one spacer... Dealers definitely have their function and place but rarely in fixing a 16 years old car.

Since it seems that once the case lock goes, the bow lock goes also, I have to take a good at it. It would be good to do it at the same time if there are signs of a problem. The bad thing is that the leak is affecting the open top season 😢

Below is a photo of the bungee system.

 

So, I managed to source the whole lock-cylinder-sensor assembly from a semi-local scrapyard for 50€ (around 56USD). When I took out the old lock it was covered in fluid.

It took me about 1,5 hours to change the lock assembly and to fill up the fluid reservoir. I cycled the open-close sequence 4 times and checked the fluid level after that and it hasn´t moved so I would call it a temporary success at least.

Obviously sourcing a scrapyard part is not the same thing as getting a faulty part rebuilt, although it came with a 15 days money back guarantee.
I´ll keep my eye on the fluid level and when the topless season comes to end I´ll go through the whole system properly and probably get some parts rebuilt.

Thank you Serndipity and Klaus for your help. If you ever come to southern Spain, the cerveza is on me