Wife has a 2012 E350. A few months ago (before it got cold) she went out in it one morning and there was an inch or so of standing water in her driver's side Weathertech floormat. The carpet was also damp, as was the driver's A-pillar.

We dried it out with a space heater for 2 days until it was bone dry, then I cleared the sunroof drains from the top with string trimmer line, ran some water down the drains with a bit of dishwashing detergent and let it sit a bit, then removed the wheels and reached up and massaged the sneeze valves to make sure they were clear. (Did this for driver & passenger sides.) I then ran water through the sunroof drains and they sucked the water down very quickly and drained out where they were supposed to drain. I also cleared the drain areas at the bottom of the windshield/firewall area where sludge tends to build up and made sure that was free-flowing. Satisfied, I put everything together. Once it dried, just as a precaution, I used flowable silicone and filled up all the gaps I could find around the top and sides of the windshield. (It has the original MB windshield.)

Two weeks later, another rainstorm, and more water in the car (though not as much, since the storm wasn't as bad.)

So I took it into the independent foreign car shop I've been going to for years. They tried getting it to leak from the sunroof drain and couldn't. Pulled the A-pillar airbags and checked all the hoses, and $200 later they couldn't find a single drip.

The weather was looking to get bad again, and since I didn't have the time to jack it up and pull the wheels and cut the ends off the sneeze valves, I just put clear Gorilla tape over the sunroof seals and said "I'll get to it when it warms up a bit." I have used the clear Gorilla tape on previous cars when I needed a temporary sunroof seal, and it works great.

After a few days of rain... we have standing water in the Weathertechs, a wet A-pillar, and damp floorboards again.

What the heck are we missing?

 

Your windows are all synced up right? I know that’s pretty obvious and you would see if they were cracked open, but that’s all I got. I commend you for checking all of the usual suspects and clearing everything out.

 

Next suspect are these areas in engine bay.

01. The front SAM uses seal, if the seal leaks that is a big hole and is above the driver footwell.
https://mbworld.org/forums/e-class-w...ak-points.html

02. Brake booster is another device which goes thru firewall between driver footwell to engine bay
03. Steering link

I would focus on front SAM first because it is at driver side The plastic tray which has the wiper, that is a leaky point at the wiper shaft seal.
Do a running water test on front windshield while removing the footwell cover and see water seepage.


I am on a RHD car, so for your LHD car what you see would be different, you can visualize still.


That is the hole of the front SAM. If there is a leak at the seal, it will be hidden under the sound shield which in my car is the grey foam






If your A pillar is wet, it makes sense assuming front SAM is the culprit.
Below is lower side of A pillar to the right of the hole of front SAM, for your car it will be to the left of the from SAM hole



Good luck.....

 

Good detective work to figure out your leak. Everything you've fixed are standard problems you've eliminated for later.


roof to pillar seam covered by plastic trim

I bet it leaks at the junction between the A-pillar and the roof. It is built with only couple spots welds to help absorb frontal crashes. A joint compound is applied to seal this loose seam but given enough stress it cracks and shrinks!
The roof lateral discharge then pours straight inside....


FYI: located at the first row seat, your main power management module (aka SAM) is setup for rain damages. It gets swamped when the rain is channeled down the harness right into SAM's enclosure tub.... long story short be sure you inspect and dry your driver side SAM ASAP, this will save you bundles.
I used RTV silicone last time to fix that defect on all 4 corners of my car roof.


SAM wide open entrance gap (I plugged mine!)

Your headlight switch module is in that down-pour area as well by way of its harness guiding water into unsealed connectors.

The windshield seam is an excellent entry point as well.


Try this to pin-point entry location....:

- strip A-pilar interior trim to see water coming in (you really want to minimize water damage by pooring as little water as necessary)

- Use a water hose around windhield sides then top horizontal then last on roof to test pilar seams. ie test spray the lower parts before the high ones.😎


A W211 related thread:
Test separately for evidence of: "Lose vs. Seam"...

overlapping roof seams detail

 

Nice touch Cali. U plugged the hole from the SAM

 

I would hate my SAM enclosure to get filled with rain. I plugged the internal access as a precaution when I had my F-SAM pulled out for inspection.

You can plug that big hole just as easily from the driver footwell area without removing SAM (rain may still be guided by individual harness wires).

Another reason to keep the driver side F-SAM within unconditioned air space is to prevent any condensation crusties from building over cooled metal.

 

Roof to pillar seam leaking from sealant delamination, I think my pano roof is of a much higher risk than non pano-roof
Albeit my car does not get sunlight because it is parked in a nice sunlight free garage, the crappy road I have and
my driving style will flex those toy-like roof a lot. Already evident from me needing to tighten my pano roof main frames before even 27,000KM.
You know, the famous cracking/whipping sound. when car climb up a driveway and body/chassis does not have equal weight load

 

I'll bet you're right on the money here. The A-pillar gets wet all the way up to the headliner, but the headliner for the most part is dry. The indie shop couldn't find the leak in the sunroof drain with the A-pillar trim removed because they were just using a funnel to put water directly into the sunroof drain, so they never tested for water seeping in around the plastic trim.

So how does one remove the plastic trim without mangling it or cracking it?

Okay, I'll look at that also... as soon as the temps get out of the teens. So the SAM entrance is in the footwell up above the pedals then? Just pull back the carpet?

Thanks!

 

I really like your approach to ductaping the leak area as a rainy day fix.
Tape over the entire roof plastic trim front/back on both driver/pass side - Use shipping tape to live less residue over paint clear coat (forget using solvents to remove glue!!)👍

Use picks to pop the plastic roof trims. Your best bet would be to get the official procedure document from Konigstiger himself 🤞

Emergency rescue for F-SAM:
-> check for any evidence of wetness...

-> don't let it soak while powered!

-> if wet then *EXTRACT SAM ASAP* for drying before oxidation start bridging the consumer grade PCB with infamous crusties!

Front-SAM does NOT feature a removable PCB like Rear SAM. It is directly soldered to the fuse board!
This module is really the marriage of a dual micro-controllers circuit board with fuse and relays.
(To attempt any worthy repair, an army of pins need to be desoldered from a double sided board... that's still cheaper than $2.5k!)

SAM access cover:
You don't have to get under the dash to gain access to this module. From under the hood you can pop the fuse cover in/out much more easily.

SAM's lid

 

Hi
I know its an old post but will take a chance and ask for a bit of help here....
I found water ingress at the junction between the A-pillar and the roof, what's odd is the fact that I don't have sun roof.....
If it does leak at the junction between the A-pillar and the roof how can I fix it ?
Car wasn't involved in any accident it also has original windscreen...in my hands since 2017 and developed leak few days ago....
I would greatly appreciate any suggestions.

 

Your W212 is leaking from the roof at the A-pilar area without the optional sunroof installed.

Well now we've got the drain tubes out of question, we can focus on your cracked roof seams - That's what this thread is about.


roof seam plastic trim cover
Leaking roof seam:
- Pop that trim and use your favorite sealer to cover the cracked seam.

- or let a body shop take care of this with automotive body joint compound.


VIP Electronics rescue:
- Furthermore read thread about your main SAM tub getting swamped straight from the roof harness.

- Disconnect batteries, keep cover open to dry ASAP.

- Keep an eye on swampy SAM with scanner. It may need replacement.

 

Thanks for your help.
It probably gonna sound a bit stupid but...Do I need to seal it from outside , removing this plastic roof trim or from inside removing Pillar A and a bit of roof liner ?
What sealant has to be used ?
And final question do you think independent MB Specialist would be able to tackle it ?
I did read all article and got a bit confused about SAM unit , I thought its under floor carpets ? At the moment I only got wet stain on the A pillar not bigger than 2cm diameter
Thanks again for your help if you any more instructions/suggestion please add them here,
Im quite devastated and depressed by very expensive faults developed by my car lately ....

 

Thanks for your response really appreciate it
It's probably gonna sound stupid but....do I remove this plastic trim from the roof and seal it from outside or remove pillar A and a bit of headliner and seal from inside?
can that job tackled by Independed Merc specialist or with basic mechanical knowledge can be done at the carpark ?
The silicone you used...where can I get it from ?
At the moment water only appears on Pillar , not bigger than 2cm diameter , fool carpets are still dry so Im guessing SAM under the carpet is still ok. If weather allows I will try to strip it down on Thursday.
Once again thanks for your help

 

Look at the windshield edge seals ? That's where mine was coming from, bc the a$$ at the dealer that replaced the windshield didn't fit them well. Or they broke them. I'll need to look up the part on that too

 

Thank you for your message. Yesterday after work as a temporary measure I applied some tape from pillar B to pillar A over the plastic roof rails, also stuck a bit of paper towel at the junction of liner and pillar A under air bag just to see if it will get weat, it did rain all night and today when I got my car it all looked dry....so I guess it leaks somewhere between pillar A and B. I was thinking if it possible that it leaks at the place where roof rails can be fitted?

 

No question the removable roof rail covers do leak because the seal is done at lower level. The plastic trim is used to nicely conceal the body welds.

The W212 windshield seal is known to leak... that's why you may want to spray test suspect areas from the bottom up. No guessing needed✌️

10mn 5¢ fix:
Having taped up the roof trim is another quick way to see if leak will stop.


$$$$:
The key is to minimize swamping F-SAM in his tub through direct delivery by A-pilar harness pictured above.

 

Having experienced wet A pillar and footwells. Water dripping from inerior mirror unit i eventually found my leak. My car has no sunroof. See pics, The narrow channel in both roof gutters between windscreen and roof rack mount point are cracked on bboth sides. Zoom in on pic to see the crack. Covered with sealer for now.

Zoom in to see cracks in the narrow channel

 

Yes I think my car had water ingress from the same place, I've used some clear sealant on the corner of the windscreen as well as from the inside under headliner close to rear view mirror and it did seal it properly. Luckily I got rid of that pile of horse s..t back in May :-)

 

Wow.... so non pano or sunroof car still uses sealant there at roof rack rail ?
Probably MB made the body to be ready for pano or sunroof and when sold/ordered without them they cover those openings ?
That is no good for stifness

 

I am about to check this as I experiencing a drop or 2 coming thru the inside top left of the windshield, and want to catch it before it gets worse.

What kind of sealant are people using, and how is it being applied.

Also are there instructions on removing the "beauty" covers?