I have had my 1981 300SD for 8 days now. Water was pooling in the rear passenger seat into the carpet behind the passenger seat. Tested and found it was coming in through the working sunroof. I love my sunroof so would never seal it up. I blew out each drain tube and water was still coming in down the rear C pillar into the seat well. Took down the rear passenger side headliner ( Thanks -> Alec300SD & Junkman) to see what is below.

Pics below after removing the rear passenger side headliner.

The drain pan obviously rusted away in the rear right corner pretty badly.
Most likely due to never cleaning out the sunroof drain tubes water built up over time and hence rusted away from the inside.

I just brushed away what I could with a wire brush and painted Corroseal over the entire rusted area of the right hand corner.

I should check tomorrow to make sure this is the only leak area.

If it's the only spot I plan to rebuild the pan and drain tube then seal it ...I am thinking WATER WELD as a good choice for this but I am open to any other suggestions on how to do the fix.

Will post progress.

Austin

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__________________
'87 924S
'81 280SEL

Sold ->

81 300SD -
93 300E w/ 3.2
85 300D-
79 300SD
82 300CD
83 300CD - CA
87 190E 5 spd
87 Porsche 924S

"..I'll take a simple "C" to "G" and feel brand new about it..."

That doesn't look like a good rebuild candidate to me.

If you are going to try it, then at least test the two products that you plan to use on some other piece of rusty steel before you proceed. The rust converter/primer products are all basically a mild acid treatment with an acrylic latex prime coat. They work OK for architectural iron that's going to be topcoated with a a water or oil based paint. I don't know of any amine type epoxy product that bonds well to cured paints of any type, and I doubt that the JB Weld product will. I think a better bet, short of finding a replacement, would be to take it down to bright metal and rebuild with fiberglass and epoxy resin.

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'79 240D

How attached are you to an opening sun roof? This type of rust will crumble when dug into.

If you do seal it up, don't use silicone as it will cause repaint issues in the future. Body seal sealer or DAP Dynaflex 230 ( that comes in a few colors and clear ) would work but might be difficult to get a neat bead.

Maybe use the above sealer and windshield trim strip. This plastic T shaped strip is used on newer cars and comes in a few sizes.

I am pretty confident I can make this a water tight patch. My concern is the existing rust inside the pan which I cannot get to unless I opened up the pan.

I've used Corroseal before on a 240D that spent winters in Boston for 20 odd years and it turns rust back into iron ore again. If done right even the flimsiest shards become solid like new metal. Still I can only treat what I can see.

I am thinking a bondo type flexible patch to shape the opening,
cover that thoroughly with 3M Wrap and Repair Silicone Tape around the
new shaped pan area, and use the 3M tape to also wrap around the drain hose and make the connection into the pan. Once that fuses to itself I can
coat the 3M tape with the Water Weld.

I am pretty sure this will hold up better than whatever is left of the existing 34 year old pan.

If anyone has details or a DIY link on how to drop the sunroof drain pan I would appreciate it much.

Thanks, Austin

__________________
'87 924S
'81 280SEL

Sold ->

81 300SD -
93 300E w/ 3.2
85 300D-
79 300SD
82 300CD
83 300CD - CA
87 190E 5 spd
87 Porsche 924S

"..I'll take a simple "C" to "G" and feel brand new about it..."

I would not own a diesel Mercedes if it didn't have a working sunroof.
Hopefully I get lucky and fix the drain tube.

__________________
'87 924S
'81 280SEL

Sold ->

81 300SD -
93 300E w/ 3.2
85 300D-
79 300SD
82 300CD
83 300CD - CA
87 190E 5 spd
87 Porsche 924S

"..I'll take a simple "C" to "G" and feel brand new about it..."

Restore step # 1

I saw first thing I had to do if this is going to work is rebuild the corner edge around the draining area.

So I cut a piece of aluminum gutter to fit inside around the corner of what was the sunroof drain track. * Interestingly the drain track is not covered on top. It is open with a cloth type seal at the top running around the circumference of the sunroof frame.

So for that I shaped my insert to reach above the felt area and around the corner, overlapping what is still solid.

I ran a bead of 3M weatherstrip sealant around the edge of the cut trim insert, held it in place for a minute to dry.

Then I am using the white looking putty which is JB Water Weld. I pressed it around the inside of the trim piece and on to the frame.

I noticed when I pushed it to seal that it also filled in a tiny rusted hole I wasn't able to see. So now that is filled in and covered too.

pic below. Working on next steps....


AA

Attached Thumbnails

 

__________________
'87 924S
'81 280SEL

Sold ->

81 300SD -
93 300E w/ 3.2
85 300D-
79 300SD
82 300CD
83 300CD - CA
87 190E 5 spd
87 Porsche 924S

"..I'll take a simple "C" to "G" and feel brand new about it..."

I would source a good part. Anything out of a 126 will work. You will spend time and effort and still have a crap repair. I've only actually seen a few with the headliner out but yours is the worst. Go to the yard and buy the whole sunroof for <$100. You already know how it comes apart.

__________________
85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

The whole sunroof pan just unbolts from the roof. It is simple to remove but tricky to get out, I took it out when I had my rear windshield out.

Your issue with the repair is that it will not solve or help anything....yeh if you plan to flip it on ebay and need a repair to hold 3 months...so be it...

The issue you will be having is soon you will notice rust bubbles ontop of the roof. You may have stopped the water leak but now you'll have holes in the roof you won't be able to fix. That rust has ate away the pan, moving up the side, in between the felt scrappers and onto the roof. The only way to stop it is to remove the roof and kill the rust...paint and apply new foam weather stripping as the pan gasket and new weatherstripping for the sunroof. The pan was never meant to hold water like a swimming pool, the drains/pan were incase the roof was left open in the rain/seals tore etc...the seals are what stops 99% of the water from getting to the pan...

If you don't get that pan down and the rust killed....your issues will be ten fold after next winter...

__________________

Some good advise here. Good luck on this project of love!

Sun/moonroofs are problematic @ some point. Fortunately, my 16-year old Texas '83 300SD's was flawless, since garaged for 305K miles under my watch. Just don't use it enough to have or want one anymore.

X2. Take down the whole headliner and remove the pan. Replace with a good yard pan, or repair this with steel. If you are not up to the welding repair, drop the pan off at a body shop. Plenty of places can weld new material in easily, especially if you do the painting and prep.

Easiest is to replace the pan if you can find a decent one. What you are doing now is encapsulating the rust, and it will be a lot worse a lot faster than you expect.

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This post brought to you by Carl's Jr.

I took a few more pictures but only posting these two.

One is the hose firmly attached ( Water Weld ) back in the exact place it is supposed to be.

I built that up on the inside and outside of the opening. I tested it after 2 hours and that is picture # 2 . ( sideways, but it is water pouring out of the drain tube on to my driveway)

After the Water Weld set I covered the entire patch and up along the sides with strips of Dynamat soundproofing. No water will come out of that corner any longer. All 4 drains are clear and ...........

For the advice of pulling the drain pan out tomorrow morning, etc... a- There is no pan up there. It is a track with drainage openings at the corners. b - I have the car a total of 9 days, and I do have other things to get to like a window off track- I think a trunk seal - shifter linkage play - cruise control - steering play - replace crappy tire on car with 4 good matching Falken Ziex tires, - and this are just the A list.

I have my leaking sunroof and wet carpet under control and depending on how things go through Hurricane Season down here June - October, where I will hopefully be using my open sunroof each evening, I'll update any leaks or rust bubbles.

If I decide, or need to ever replace the sunroof drain track I'll check back for the great advice we all get here.

Attached Thumbnails

   

__________________
'87 924S
'81 280SEL

Sold ->

81 300SD -
93 300E w/ 3.2
85 300D-
79 300SD
82 300CD
83 300CD - CA
87 190E 5 spd
87 Porsche 924S

"..I'll take a simple "C" to "G" and feel brand new about it..."

The ambient high humidity level of Boca Raton, FL. coupled with the airborne salt and rain ALL conspire to rust on old cars. in your area.
If you can store your car out of the weather, it would be a plus - going forward.

I've been fortunate enough to be able to garage ALL my old Mercedes-Benz cars the last 25 years. I even have a de-humidifier AND AC system in my big garage the past 5-years as well!

Thanks.

The car has very little rust and most of it is surface. As I have the time I'll treat and "kill" as much as I can find.

I do have a garage and have thought about AC'ing it. Before I do that it would need a thorough cleaning up.

__________________
'87 924S
'81 280SEL

Sold ->

81 300SD -
93 300E w/ 3.2
85 300D-
79 300SD
82 300CD
83 300CD - CA
87 190E 5 spd
87 Porsche 924S

"..I'll take a simple "C" to "G" and feel brand new about it..."

I was fortunate in that my 50-Gal. water heater is a heatpump model. Rather pricey, but boy does it do a number on de-humidifying AND cooling with DRY air by wringing the water out of the air in the square footage of my double garage that I house the Mercedes-Benz in. I would definitely de-humidify the area if nothing else if you plan to dote on any old/aging car. Heat in a garage won't harm the car too badly as humidity will. Besides - keeping the car out of the deadly sun and possible hail/salt-air is a big plus down there.

What we are saying is the entire sunroof assembly is bolted to the roof. Track/pan/whatever, the whole thing drops out and is connected with ten to twelve 10mm nuts on studs coming down from the roof.

Typically it is called a pan.

Keep your eye out for another one just in case in the yards since this issue will return. They can come out through a door if you remove all your seats.

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This post brought to you by Carl's Jr.