Bugsi

My 2005 S500 4MATIC was having repeated ticking from the trunk's driver's side any time I'd sit in the car after driving.
I did a little research and read that it was probably the PSE pump in the trunk running, and confirmed that by putting my hand on it. (I already have the trunk carpet on the driver's side out for some previous work on the radio components in the trunk.)
Today I took the PSE pump out and disassembled the turbine stack to inspect it, and I was surprised to find that it all looked okay, No broken vanes or hub assembly. I carefully reassembled it, keeping everything in order and aligned (I'd marked it first) and tested the pressure. It put out over 45 PSI, (over 3 Bar) so the pressure is okay. I reinstalled, and just for good measure pulled the 20 amp yellow fuse under the back seat, then reinstalled it.
The PSE pump whirred to life and stopped, so I tested all four doors' soft-close function. On three of the doors, the pump ran for a second or two when I open the door, and again on soft close. But for the driver's door, it ran for about 12 seconds and then stopped. I tested this again around the car and got the same result.

So I know I have a working PSE pump, but it runs for about 12 seconds when I soft-close the driver's door. Does this indicate a leak at the driver's door soft-close module? Are there known issues with how-to repair guide info for dealing with these? I'm not sure what the pump running for 12 seconds on the driver's door soft-close is supposed to mean. Help me Obi-wan!

wallyp

Most probably a leaking pneumatic actuator. You can expect the PSE system to shut down that function soon.

A search on this forum or on BenzWorld will give you dozens of helpful threads. A web search on W220 soft close will give you lots more info, including several YouTube videos. You will need to learn how to remove the "door card" (upholstery panel) and how to repair or replace the actuator.

Bugsi

Thanks. I've reviewed a bunch of videos on it now, and yes, it looks like I'm in for taking apart the driver's door and removing the actuator module to inspect for cracks or faults. (I've previously repaired the trunk soft-close manifold by epoxying the cracks on the manifold pipes that are blocked off at the factory with steel ball bearings jammed into the plastic tubes, where the tubes crack around the steel ball bearing.) I'm no stranger to taking apart car doors on early 2000's Pontiac Grand Prix's and Bonneville, but wow, getting the actuator out of the driver's door of a W220 looks like a pain in the butt. My S500 is my daily driver, so I'll have to wait for a weekend when I don't have any plans to take the entire thing apart.