In my 'shop today, W176 with a pond inside...

[Uncle Benz]

The foam backing on the carpet can hold a lot of water. It takes a good while to get it dried out once you have stopped it getting in. I’ve had good results from parking the car on a downhill slope. It then moves to the front. You can remove the sill trim and pull the carpet up in the footwell to hoover underneath

 

[joderest]

water ingress is such a pain to deal with, see my post, been at it three months now. Problem even worse when more than one leak arriving at same place ?.
The foam under carpets does hold loads of water, the only way is to put towels under them to soak the water away, a tumble dryer and about six towels are your friends. Sometimes two or three times a day.
The really annoying thing is you get to the stage where it is just damp, and it leaks again so back to square one. I do not know yet if my leak is fixed, as i think i still have water trapped under the dash which runs out when you drive. Waiting for todays and tomorrows wet weather.

 

[Bryan Giggs]

Hi all,

Firstly thanks to Uncle Benz for the guide, it was very helpful.

I thought I’d add a couple of things that I found, I had a very small amount of water in the spare wheel well so thought I’d tackle the problem before it got worse.
I bought the new vents direct from Mercedes as they were about half the price of those on eBay, the new ones were slightly different as they had an added layer of foam as seen in the photo, but I still added some sealant just to be sure.
The job was not as daunting as it seemed and following Uncle Benz’s guide was a big help. One thing I found when tackling the 2 nuts on the long splines, instead of using a deep socket I used a 10mm angled head ratchet spanner as seen in photos.

Hope this helps anyone doing this pain in the a###e job.

 

[star]

Did you look at the grommets behind the rear lamps, the become loose?

 

[Uncle Benz]

That looks to me like they have updated the part again. The foam bit is something new.

 

[Dubz79]

I had mine fixed for free by merc back in 2018 (mines a 2014), it's back again and they say they have no knowledge of the issue even though they were the ones that did the work 2 years ago.

I've had upto 1cm above the carpet...

I bought some and fitted but i'm still leaking, i pulled up the rear seats and pulled out the little rubber bungs and you can see water coming through from the rear still.

Question is it's my passenger side like most that fills with water but it's my drivers side tail light that has the moisture in in currently, driver side is bone dry.

Surely something can be made to divert the water away from the area around the vent!

 

[peterws1957]

they say they have no knowledge of the issue

Seems to be the default response to well known issues from some MB dealers.

 

[Impasto]

This is a very common problem. Manifests itself as a puddle in front and rear foot wells, most commonly on just one side of the car to start with. For quite a while Mercedes were fixing these for free, but that seems to be getting rarer now, and in fact a lot of cars are coming in for their second time. Air vents behind the rear bumper are the root cause of this fault. Mercedes have superseded the original part number, but to be honest I cannot see any difference in the part, so it will likely rear its ugly head again in time.
First step is rear bumper off...

You can see the two vents just below the black bumper reinforcers. This is with the vents removed...

This is the vent itself. You can see the yellow/cream soft rubber seal. This is the problem. It stops sealing and rainwater sneaks in between the body and the seal. From there it tracks along behind the inner arch trim and sluices down under the rear seat onto the floor.

The design is not that clever. The rear lamp seals to the body with a triangular foam, and rainwater drains behind the body of the light itself, through the back of the bumper reinforcer and straight onto the yellow/cream seal of the vent.

To fix the problem for the longer term I fit some new vents, but clean the mounting area thoroughly with some degreaser...

And apply a bead of silicone sealer to the yellow/cream edge of the new vent...

With the new vent clicked into place a satisfying splodge of silicone oozes around the edge. It matters not how it looks, because the bumper hides it all...

All that's left to do is refit the bumper.

Thanks for the write up and i solved my problem with this post

However instead of changing the vent duct, i seal it with soundproofing tape. I wonder if this is ok? Anybody knows what does the vent duct do? Can i seal it like i did?

 

[Blobcat]

Thanks for the write up and i solved my problem with this post

However instead of changing the vent duct, i seal it with soundproofing tape. I wonder if this is ok? Anybody knows what does the vent duct do? Can i seal it like i did?

It lets air out of the car, so when you close the door the air has somewhere to go

 

[Impasto]

It lets air out of the car, so when you close the door the air has somewhere to go

so now that i sealed it shut.. will it cause any long term issues? i was told that sealing this way will solve the leakage problem for a longer time.

anyway, the floor is still wet. any products u know of that i can put in my car to absorb the moisture?

Thanks

 

[Blobcat]

so now that i sealed it shut.. will it cause any long term issues? i was told that sealing this way will solve the leakage problem for a longer time.

anyway, the floor is still wet. any products u know of that i can put in my car to absorb the moisture?

Thanks

You won't get fresh air into the cabin as easily as it's more difficult for it to get back out... also the windows could rattle a bit when closing the door as again difficult for the air to get out.

Dehumidifier either silica gel or electric