S212 Trunk hatch trim is holding water
 

Discovered today that the plastic trim at the lower edge of the hatch was holding water from a recent heavy rain in bone dry SoCal.

The water drained out the moment that I opened the hatch. Dripped water from both corners of the bottom of the plastic trim where the handles are located.

My goal for tomorrow is to open up the area to dry it out and start troubleshooting.

Does anyone have insight on how to remove all that stuff?
More importantly, any theories on where the rain water entered in from? The tail lights on the hatch seem the most likely candidate.

Thanks

I believe that's where I would start. It strikes me that it could also be the seal around the wiper motor shaft or possibly through to the wiper motor and then down. I've noticed that the wiper shaft on mine (at 80k) has a whole lot of play in both in the shaft itself and in the gearing -- not that I was looking for a leak, but that seems to me like a possible place for water to get in if the shaft bushing/bearing/whatever-is-there is worn enough. Mine's not leaking, but it struck me earlier today washing the car that it could and I ought to look into it.

The wiper shaft seal is not completely stationary. I mean I can turn it a few millimeters CW or CCW. But it is snug up against the glass. Entirely possible to leak there but I estimate about a half a cup of water dripped from the left and right corners combined. That's a lot of water to migrate in through the shaft.

See if attachments helps.

What I meant by movement was not the play up and down the glass by the wiper, but rather the general play in the wiper shaft that sticks through the tailgate. Yeah, that's a pretty small hole to get cups of water through so I certainly wouldn't start there. That said, water could accumulate over time...

More likely is the seal for the assembly where it attaches to the exterior.

Anyway, I thought you were right about starting with the tailgate door lights. That's certainly more surface area to leak. If it's not obvious there, you're going to want to pull the tailgate interior panel to figure it out. Look for streaks. That will point to the culprit. Looks like Konigstiger just sent us the details on how to get that interior panel off while I was typing this. ;)

Thanks maddenma and konigstiger for the tips and WIS respectively.

I was able to find the WIS with the Mercedes Virtual PC - took me 30 minutes. I still don't know how to create a pdf on the virtual PC.

Lower plastic trim was easy to uninstall thanks to the WIS from Konigstiger.
Found water weeping from the mounting slots in the hatch where the trim grommet press fits into the hatch.

In other words, the water is pooling inside the hatch door where the metal pieces are spot welded together.
Need another couple of hours and day light to peel away more interior ... It'll have to wait until Saturday.

Update to this thread ... thought the leak was resolved by replacing the o-rings for the star badge. This past week we had another couple days of deluge and discovered more water. This time I had the dealership troubleshoot and they discovered that the 3rd brake light is not sitting flush to the trunk sealing surface creating a gap. Dealership claimed that the brake light and nozzle need to be replaced for $700. Considering doing the replace myself for $170. Planning to visit the tech later today.

Anyone have the WIS to remove and replace the 3rd light?

So thankful to spend 10 minutes with the tech Friday an hour before his shift ended. Asked him to confirm the root cause. He claims that the wire connector for 3rd brake light was folded and sandwiched between the paint and the sealing gasket causing the gap. The connector is cracked not the light.

Anyway, looks very straight forward now that he has the three panels uninstalled. They appear to be all push type fasteners. I decided to have the tech leave those panels as is and I will install a new 3rd light because the wire connector is broken and I don't where to get the connector.

The leak is back.
Had a fairly big rain day here is SoCal this week. Popped the hatch and verified a about 1/4 cup of water dripping from both corners of the tail gate.

Gonna have to strategize on the root cause this time.

Have you looked for drains in the bottom of that chamber that have open cell foam screens that may be clogged?
Where water can get in, the engineers have generally given it a place to get out. Like doors and tailgates...

That particular gate assembly does not have any drains. the leak is inside cavity of the tailgate. For example, pull all of the plastic trim off to expose the bones that the harnesses and wiper motor attach to, etc. - water is collecting between the outer mold line and the inside structure where factor seam sealant exists. As soon as the gate is raised beyond 6 feet, the water drains out of the cavity thru the adjoining trim.