Before you skip this post, let me say that I have read most of the threads on water leaks here, and I followed all the advice.

My 300D was taking on major water on both sides, front and back. I used weed trimmer string to clear out all drains. I removed the battery and repaired a hole under the pan. I made sure the drains under the hood were draining freely. I removed the wiper vents and found no holes there. I hosed her down good and found no leaks.

I then replaced all interior padding and carpets (ruined by PO). Last week I took her for a ride on a very rainy Friday. I returned home to find the passenger side was completely saturated! I used a shammy cloth to remove about 5 cups of water.

Today, I rechecked all the drains. All were still clear that I could see. I stuck my finger in the side member drain (between the front and back doors on the underside), and about 2 cups of water poured out. What area of the car does this drain? How do I prevent it from getting clogged?

I then hosed down the car for a good 10 minutes- no leaks anywhere. Did I fix the problem?

Is it possible that the floor drains are dry-rotted and allowing rain water from the road to splash into the cabin? If so, why was only the passenger side wet.

Sorry for so many questions, but as you can imagine, this has been driving me nuts! I put a lot of time and money in the interior, and I don't want it ruined. Or for the floor to rust out.

Thanks,
Avery

1985 300D, 257K

I've found out that 99% of interior water leaks come from the front and rear windshield seals. Does any of your windshield seals have cracks or are hard? On my rear windscreen I filled in the cracks but because the seal is hard, the water runs under the glass into the cabin....

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Take a look at all of the rust repair I did on this W123, it should give you a better idea of where the leak may be hiding.

Who has the most rust and still drives


.

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1985 300SD
1983 300D
1984 190D
2003 Volvo V70
2002 Honda Civic

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I am not sure but I think it is part of the Sun Roof Drains.

I know for sure there is Rubber Plugs in the Back that can be removed to drain the Water out. I have not paid attenion to the Front. But, it is reasonable there is Rubber Plugs there also.

I had rusted through holes in the pockets where the Hood Springs retract in to.
I also had holes under the rubber of the back Window seal at the bottom right corner.

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84 300D, 82 Volvo 244Gl Diesel

Assuming your car is a four door saloon / sedan...

...the rubber "drain" between the front and the back doors is just a plug with a hole in it.

The sun roof drains come out at the front of the car just in front of the A pillars between the wing / fender and the front bulkhead / firewall. The rear sun roof drains come out on the C pillars in those funny gucci vents that look like they provide cabin ventilation (they don't) - they are just above boot / trunk height.

(Just in case anyone reading this doesn't quite get A pillar B pillar C pillar => Pillar (automobile) - Wikipedia, the free encyclopedia)


I agree with those above who say windscreen rubbers and those spring pocket recesses.

If you remove the trim on the side of the front foot wells I reckon you might stand a chance of finding some evidence of wetness.

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Strange question, do you know if Mercedes ever installed insulation in those pillars? On my 78, there is a bunch of coconut fiber sticking out those strange vents....I have always been curious as to what the heck is shoved in them and why....

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Thanks for the replies. I will check the windshield seals again, but they looked ok for the most part.

WHunter, thanks for the link to your rust repair project. My 300D has a lot of rust around the rear quarter panels, with the right one going through the trunk floor. I wonder if this is playing a role in the water leakage. I've priced out a pro repair, but I can't see paying $1500 to repair a hobby car I bought for $700.

Evacuate & secure compartment then offset with pressurized air. Counterflood if necessary to negate list...

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Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership

I just got done making my 300D water tight, it was about a month ordeal.

The window seals are deceiving. They will look fine, but they can be leaky as all get out! My front windshield seal had been replaced before, but it was a non genuine MB seal, and it looked great, but needed some work to get water tight. I ended up going to the auto-parts store and got this stuff called flowable silicone, it's very light silicone for sealing windows. There's all kinds of debates as to whether it should have to be used, how long it last, etc. But short of replacing your window seals with genuine MB seals, this is the next best bet. My window seals leaked before, but with some strategic water pouring and finding leaky spots, they don't now.

You need to watch and observe to all of the spots were water drains when it rains.

One spot to check is behind the decorative gutter trim on the C-Pillar. There is a recess in the body where the sunroof drain drains out of, and water flows through there as well with rain. I found the bottom spot of this body recess had a little rust hole on it which would allow water to leak down and it would flow some into the trunk, and some down under the side of the back seat onto the floorboard. Did a nice rust treatment and patch, and no more leaks there!

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1984 Mercedes-Benz 300D

Check behind the rear window between it and the trunk lid. You'll probably see that the small area between the two is rotted out,,,, if so rear windshield, but and there's always a but, front passenger under and around the battery tray. There are drains there that need to be cleaned out.

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Closing the store
Benzbonz.biz on your smart phone or tablet.

'Cos my car came from Switzerland I thought it was mountain lichen!

I don't know why it is there - well was there in my case...

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

When I cut mine out of the my car I could not believe how much muck and dirt was stuck between the glass and the rubber. No wonder the seal was leaking - like you say it didn't seem like the seal was a problem until I cut it out and I could see that it was.

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Oh man, I forgot to mention that. I know just what you mean. My front window was pretty clean, but the rear window was BAD!

To the OP, if you find leaks in the windshield seals, get yourself a set of small hooked screw drivers, and put a cloth over it and drag it under the seals to clean the grooves. You'll have to make multiple passes. Short of taking the window out, that's the best way to clean it.

Some people even say just cleaning the grooves fixes there leak. Either way, you want the grooves clean before you put silicone in there, if you have to.

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1984 Mercedes-Benz 300D

What about compressed air????

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Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership

i have the same problem right now actually created by the monsoon we had a few days back on the east coast...

the best way to diagnose is to take the passenger side carpets out, as well as the lower trim underneath the glovebox.

when the water comes again, you can reach right up and find the wet spot. and you arent soaking the carpets again.

as others have said - windshield seals are a likely culprit. im reeeeeely hoping thats not the case with me, my seals are only a couple years old.

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car