Make & Mend

Article by Joe Hall

An Open & Shut Case

Fixing a broken convertible top

As I mentioned in my article about acquiring a 2002 CLK55 (see page 58-60), the seller told me up-front before we looked at the car that the top was in reasonable condition, but the folding mechanism wasn’t working and the top was leaking. Non-working tops are a common issue on CLKs so we weren’t scared off by that problem.
After determining the luggage cover and trunk lid were in the correct positions, I checked the ground wire, which is in a location where it bends every time the top is opened and closed. It can break after years of operation. Sure enough, the ground wire was broken: an easy fix with wiring pliers and some electrical tape and the top was operational.
However, just recently the convertible top stopped working again. A hydraulic-fluid stain in the rear of the luggage space under the hydraulic cylinder operating the rear bow-lock was a good clue why: The fluid seal must have blown on the cylinder. The specialists say that this is an almost unavoidable problem on every Mercedes-Benz convertible built after automatic-top mechanisms were installed in 1989; these seals typically last only 10 to 15 years, though your mileage may vary.
Checking first with a Mercedes-Benz dealer, I learned that new cylinders were available, but cost approximately $500 apiece. Not only that, the cylinders required a full day of a technician’s time to install because of all the parts that had to be removed to access them.
However, a little research led me to one of the advertisers in The Star magazine, Top Hydraulics, located in Oregon. Owner Klaus Witte told me that his company replaces the seals and rebuilds the cylinders to sell on an exchange basis for a fraction of the price of a new cylinder. He assured me that any person who was careful and reasonably handy with basic tools could do the replacement at home. Witte strongly recommended that I replace both cylinders in that area at the same time because the same disassembly and assembly would be required for each; if the seal had failed on one cylinder, he said, it would soon fail on the other.
The company’s procedures don’t require removal of the hydraulic cylinders from the locks, which not only saves an installer time and frustration, but also prevents damaging the cylinder rod (if rods are damaged, it reduces the core return based on the amount of damage). Top Hydraulics’ website has step-by-step, start-to-finish instructions that includes color pictures of the areas, parts (push pins, clips, and so forth) and tools needed to do the job. One thing I really loved about the instructions is that they weren’t written in engineering jargon.
While awaiting a two-day delivery of the two cylinder locks I ordered, I downloaded the instructions to my tablet so I could have them nearby the car as I worked. For novices like me, I recommend reading the instructions several times and allowing plenty of time so you won’t be under pressure to complete the job. I did the disassembly and removed the cylinder locks the day before replacements were due to arrive. Removing everything necessary to gain access to the hydraulic pump was the hardest and longest part of the process. No wonder Mercedes-Benz techs hate working on W208 hydraulics.
It did take me several hours for the disassembly. Because my hair is gray and my memory isn’t as good as I’d wish, I labeled sandwich bags for each part and panel I removed (there are lots of little parts) and took digital pictures as I worked. This was extremely helpful for the reassembly process.
The actual parts to be replaced had seven hex screws between them and took no time to remove and replace; to get to that point, I had to remove a very heavy structural panel that must have had 30 10mm hex head screws holding it in place.
Someone had apparently already worked in this area of the car; some of the fasteners were missing when I started the job, so I didn’t feel like I was crazy when I came up short during reassembly. Once I had access to the cylinder locks, actually replacing the bad hydraulic parts with the new preassembled cylinder locks is pretty straightforward. My pictures and tagged baggies identifying stored parts made reassembly much less confusing than it could have been.
I was rewarded with a functioning top. The best part was that total parts cost – after core exchange – was $190 plus part of a quart of Mercedes-Benz hydraulic top fluid. New Mercedes-Benz parts would have cost more than $1,000 and would be warranted for only a year. Top Hydraulics warrants their rebuilt parts for three years.    
With the top operating again, I dealt with the leaking and faded top material. Online I found Renovo, a highly recommended top cleaning, recoloring and waterproofing system. Two tips: Make this a several-days project to allow complete drying between applications, and mask and cover all exterior areas of the car, just as if you were spray-painting a panel, since these materials can damage or discolor paint surfaces.
The biggest challenge, really, was to remove the hydraulic fluid that had leaked inside the trunk. This fluid has an unpleasant smell that does not dissipate. I used kitty litter to soak up the excess fluid, and vacuumed up the residue. I soaked the removable carpet mats overnight in a mixture of hot water and Dawn dishwashing detergent, which took care of the smell.
I’m very satisfied with the results. For a reasonable investment of time and the purchase of some parts – rather than the excessive cost of entirely replacing the top – we now have a functional top. It can be folded away on fine days – our main goal in buying a cabriolet – and erected quickly from inside the car to keep the interior completely dry despite the torrential rains we’ve experienced this past spring on the East Coast.