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Recently I discovered that there is a water leak inside the trunk at the right side.
I suspect that it is due to plugged rainwater drain pipe. So far I can’t find where exactly this pipe is located.
Does anyone have the schematics of the right side quarter panel of 2012 C300 ?
I was changing my back brakes today (w203) and to be honest i couldnt see the drain either when i was under there with a torch.. (my fuel drain was blocked though) Done a bit of googling and ive seen some drains that appear to be near the rear wheel arch. and apparently my model has a drain under the spare wheel.
You can always pour a bottle of water on the back window and see where it goes
No schematic but I have a 2010 shell that has the rear sam module removed and on the 2010 thats where the drain is. If it is turns out not to be your sunroof drain than it is possible that one of the clips/grommets that holds on the black plastic trim on the sides of the trunk opening (on the body not lid) could be deteriorated and letting water in
W204 C200, BMW E30 M3, 1980Gt Mini, Toyota Corona, KTM 200 EXC.
Hop in the trunk with a torch, have someone hose down the trunk see if it leaks then flow water down the sunroof drains find leaks and hop out of boot.
I also had a passenger side water leak in the trunk and believe I have located it. There are 4 rubber grommet/push pins that go through the plastic trim piece and the body of the car on each side of trunk. One is circled in this pic:
In this pic two are visible and circled and the arrow is pointing to the one in my car that dry rotted and is leaking water into the curved plastic piece below.
Its letting water drip in filling up the curved plastic piece and dumps into the trunk when opened. Dealer has these in stock and I will update with part number Wednesday when I pick them up.
Just fixed the same issues on my 2012. After taking my car through the car wash, the stereo speakers started to buzz and short out. 2nd time it happened I read that it sounded like water near the amp. I looked in the trunk and found water pooled by the battery. Dried things out with a fan and the speakers worked again...until I took it through the wash one more time. I had the rear bumper repaired a few weeks prior and saw a post how water had gotten in through frame rails and into the lower trunk area and had the body shop take a look. That's when they noticed the dry-rotted trim cover "plugs" and had one completely missing. It's kept the rain out so far, but haven't tried a car wash yet...
I believe the part is called
Rear Body Panel Trim Panel Clip - Mercedes-Benz (000-991-47-95)