2005 Mercedes-Benz CL65 AMG: Active Body Control Failure and Repair
March 13, 2014
We knew going into our test of the 2005 Mercedes-Benz CL65 AMG that its Active Body Control (ABC) System was a potential crutch. The life of its components averaged about 60,000 miles according to many owners. When the ABC system acted out for the first time at 58,900 miles, we weren't completely surprised. Now, just 1,500 miles later, it's failed again...
Last time, the ABC warning light alerted us to a ruptured high-pressure line. This round, a pool of hydraulic fluid beneath the car was our cue something was amiss. No light. We popped the hood to find the system purging fluid. We drove it to our nearest dealership for service, W.I. Simonson Mercedes-Benz in Santa Monica.
Early the next day our phone rang with news on the CL65. "We determined that one or more of the damping sphere valves has failed," our advisor began. "The valves are inside the spheres, so we can't tell which is to blame. We recommend replacing all four."
The spheres, or accumulators, house nitrogen gas in the upper hemisphere, hydraulic fluid in the lower and have a membrane separating the two. The gas chamber is sealed under pressure. The liquid side has a valve that allows fluid to pass in and out of the accumulator as needed to absorb road imperfections and minimize body roll. In our car, one of the valves failed, no longer allowing fluid to fill the accumulator. With nowhere else to go, it was pushed out of the overflow reservoir and onto our garage floor.
These accumulators tend to fail in two ways. 1.) The membrane is compromised. It can rupture or, with time, the natural passing of gas through the membrane depressurizes the sphere to the point it no longer damps as intended. 2.) The valve can fail, keeping the hydraulic fluid from holding up its half of the deal.
Our initial phone conversation with Kevin, our advisor, was extensive. We weren't about to okay the $2,600 estimate until we understood the situation fully. He did a good job of answering most of our questions at that time. Those he could not answer we put on hold until he could consult with his mechanic and call us back.
The second phone call started a little shaky. At this point we still had not approved the work. We talked some details of the job before I asked, "So how much did you say this was going to cost us again?" Kevin replied, "Let me add this up. It will be $3,050 with tax." I reminded him that the original estimate was $2,600 and asked what had changed between then and now. He said, "Let me add this up again. Okay, $2,700 out the door, tax included." I repeated this amount aloud. He responded with, "You know what? I quoted you $2,600. Let's stick with $2,600." We felt a bit put-off by this dance. But our research showed this to be a reasonable price for the work involved. We okayed the job.
This was the only awkward interaction in our dealings with Kevin. He was otherwise attentive to our needs and quick to respond to our questions. At our request, he made arrangements for us to take a few photos of the work in progress and speak briefly to the mechanic operating on our CL65. Admittedly, he had just learned we were with Edmunds. I can't say if this granted us backstage access, but I'd like to think any concerned owner could get the same treatment.
Overall, we were pleased with the level of service received. And even more so that the estimate overshot the actual cost.
The right-rear accumulator is tucked up above the exhaust.
The right-front accumulator is easier to access.
Access to the left-front sphere requires removing the wheel shroud.
The left-rear wasn't visible when we arrived, but here is its replacement.
All of that shiny is hydraulic fluid from the overflow.
Total Cost: $2,141.27
Days out of Service: 7
Mike Schmidt, Vehicle Testing Manager @ 60,045 miles