Cabin Water Leak

[DavidBrough]

I seem to have a problem with water leaking into the cabin which got quite bad recently due to some very heavy rain. I think I’ve tracked it down to the scuttle air vent and heater plenum and it seems that the water is making its way into the heater and then leaking out of the bottom of the blower box onto the transmission tunnel and down into the foot wells. I have checked the air vent drain tubes which are in good condition and do not leak and allow water to flow freely into the engine compartment. It seems that the water must be getting over the turret edge that protects the heater box and under or over the control flaps into the cabin. I would be keen to know if anyone else has experienced this problem and if there is supposed to be a drain at the base of the heater plenum or is the design supposed to ensure that water doesn’t enter this area. It would be nice if I could fix the leak without having to remove the blower unit and any suggestions or ideas would be gratefully received.

I enclose a couple of pictures of the offending area showing the control flaps which seem to be being breached.


David Brough
1969 280SL Auto with A/C & 3.46 Axle



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PROGRESS UPDATE

After more messing around with the hosepipe I’m not so sure it’s the heater plenum that’s the problem as the leak seems to be coming from the bulkhead box section where it joins the transmission tunnel under the blower unit as enclosed photo. Water is obviously getting into the box section and coming into the cabin at the panel join.

I now think the cause is probably the windscreen / windshield rubber as the leak is worst when water is sprayed down the screen onto the lower part of the rubber. Does anyone know if a leak here would allow water into the front box section and down the back of the blower?




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[66andBlue]

David,
it looks like you are missing the filter element that prevents water from running into the air distributor box.
I remember that some members here have made this filter from regular A/C foam sheets but it was pointed out - by Hans in Sweden I believe - that this filter must be water repellent but not air tight. Over time it will deteriorate and water goes through.
While regular open cell foam will let air go through it also doesn't repel water efficiently. I bit the bullet and bought the expensive M-B replacement filter.

Also I assume you removed the lid on the air intake when you took the pictures.

[waqas]

Alfred,
Thanks so very much for all the great pictures you've been posting-- I can't wait to see your car in person!

My air filter wires are a bit jumbled (previous owner probably didn't know how they should've been installed). Looking at your picture, it's clear to see how they should be... thanks!

I think for now I'll just thoroughly wash the filter and then change it sometime later with the original MB part.

[DavidBrough]

Hi Alfred,

I do have the original filter element but just removed it and the flap to take the pictures of the flaps that I thought were the cause. However, after much poking around I couldn’t see any signs of water ingress into the heater box and now think the problem is the screen rubber. The water seems to be getting into the box section of the bulkhead and coming out under the blower at the seam join with the transmission tunnel. I put some tape on the glass/rubber joint and that seemed to stem the flow so I will now get some screen sealer to see if that helps whilst I order and fit a new rubber. I was also thinking about changing the filter with some cooker hood filter but now I know it's supposed to be waterproof I'll leave well alone for the moment


David Brough
1969 280SL Auto with A/C & 3.46 Axle

[JamesL]

David

The cabin air filter pictured is available from MB in the UK - Mervyn at Jacksons of Bournemouth has them in stock.

I had a similar problem but since changing the filter (and flap seal) and giving the area a good clean, have had no problems. However.... I have not been out in the heavy rain since!! (That may change the coming week)

[66andBlue]

Hello David,
I am glad you have the parts. Looks like that you are on the right rack with the windscreen seal. Still you might want to take a hose and see how well the flap seal closes the air intake compartment and how well your filter is performing when you throw water right on it.

[DavidBrough]

I always find water leaks difficult to trace and this one proved no exception. It appeared for all the world like the water was coming out of the blower box which meant the leak must be in the air intake but I couldn’t see how or where. I had discounted the screen seal as it looked fine and the leak was from the bottom of the cabin not from the top under the screen. It was only when I managed to crawl right in that I noticed the water coming out of the box section behind the blower. At first I thought it must be the three screws that mount the back of the cowl to the scuttle panel but a piece of tape soon sealed and eliminated that so it had to be either the wiper spindles or the screen. I don’t think it’s the wiper spindles but still can’t quite see how water manages to get past the screen rubber and into the body panel but it just can’t be coming from anywhere else. Hopefully a good dose of window seal will confirm the culprit and a strip down will tell me the how/why, I can only assume that the seal has cracked internally and the water has found a gap in the welding.



David Brough
1969 280SL Auto with A/C & 3.46 Axle (and paddling pool)

[bpossel]

Another possible source of water leaks could be the rubber seals where the cables come through the firewall.  There are also 2 rubber seals that surround the rubber hose for the window washer bag.  These are small holes, but in heavy down pours, could be an issue.
Just another idea...
Bob

[DavidBrough]

Thanks Bob,

I had spotted those and gave them plenty of hosepipe attention so I’m fairly certain they are not causing any leaks.


David Brough
1969 280Sl Auto with A/C & 3.46 Axle (and paddling pool)

[Jonny B]

Could the water be making its way in from the wheel well, through the seal that should be in place around where the rear part of the front wheel well and the body come together. There is a black plate bolted into place with a rubber seal around it.

[stassenk]

Hi David

I've got the same problem with my 280SL.

I've replaced the carpets last week, but the car was standing outside in the rain and when I drove off, a couple of litres fell on my feet! My new black carpets are full of brown water stains! I will first replace the air vent drain tubes and the flap seal and hopefully the problem will be solved!

Good luck with the water leak!

Kind regards

Kurt Stassen

[mbzse]

quote:Originally posted by stassenk

I've got the same problem with my 280SL. I've replaced the carpets last week, but the car was standing outside in the rain and when I drove off, a couple of litres fell on my feet!../... I will first replace the air vent drain tubes..../...

Usually the kind of problems I see described in these postings are due to the two underdash drain tubes
(that extend down from the scuttle box area around the vent/heater) having become clogged.
Run a (piano) wire and also a small round bottle or rifle cleaning brush through the tubes.
Make sure no dirt/debris/rust remains in there.

The upper /lower metal drain tubes are joined by a short piece of rubber hose -
make sure rubber is intact, otherwise exchange.

I attach a pic courtesy/borrowed from/ someone on the web...


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[waqas]

quote:Originally posted by DavidBrough

I now think the cause is probably the windscreen / windshield rubber as the leak is worst when water is sprayed down the screen onto the lower part of the rubber. Does anyone know if a leak here would allow water into the front box section and down the back of the blower?

If the windshield seal is the source, then the windshield air vent passageways are likely culprits for directing the water to the blower. These are two wing-shaped cardboard vents for directing air from the blower to the base of the windshield-- one for the left and the other for the right half of the windshield.

The water could either be trickling into the vent passageway, or just down the side --allowing it to accumulate at the lowest point of the blower before launching for freedom.

[stassenk]

The upper /lower metal drain tubes are joined by a short piece of rubber hose -
make sure rubber is intact, otherwise exchange.

Thank you Hans...the rubber hoses of my pagoda are either cracked or not intact. I will rather replace them. I've already cleaned the drain tubes, because I thought that was the problem.

[DavidBrough]

The plot thickens.

After much wafting of the hosepipe I’m not sure the screen or scuttle air vent are the cause of my leak. The water is entering the cabin from the box section at the back of the engine that runs over the gearbox at the front and above the end of the foot wells on the inside and I couldn’t see how water could get there from the screen. It may be possible from inside the air vent but that remained dry as the water drained out through the drains into the engine bay. I then thought that the tubes that took the water from the air vent through the box section in question were corroded and leaking so I blocked both sides with tape and let water sit to see if it leaked into the cabin but all remained dry. I then noticed a drain hole in the engine bay as photos 1 & 2 and when I played the hose over the area water flooded into the cabin from the box section in photo three. The hole in the first two pictures looks like a proper drain so I assume its exit must be blocked. Does anyone know if this is the case and how/where it should drain so I can unblock it. I also assume that the drivers side is the same but can’t see as the area is obscured by the brake servo. I think the leak has been there for some time but as the car hasn’t been out in any significant rain until recently I haven’t really noticed it. I hope this explanation makes some sort of sense and any ideas on how to cure it would be most welcome. The bulkhead photo in my original post shows the drivers side area leaks.




David Brough
1969 280 SL Auto with A/C & 3.46 Axle (and increasingly large paddling pool)


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[Naj ✝︎]

Hello, David,

I think you may be missing a couple of rubber bungs.
These holes were discussed many moons ago (maybe not even on this site) and not sure why they are there!

Will endeavour to find the part #.

000 997 3320 Plug (in cross member above toe board) x2
000 987 0415 Plug (square - in wiper motor surround) x1 if yours is cracked and dry



naj

[DavidBrough]

Well it looks like the leak is finally cured with thanks to Bob Possel’s restoration photos. After I had managed to narrow it down to the bulkhead box section I used Bob’s excellent photo records to view the area on a clean body shell and noticed there were drain holes into the inner wheel arch. On my car one was fine but the other was not there at all. I had a foot well replaced about 2 years ago and the seam had been welded flush where the drain should be so I drilled a hole and about a pint of water rushed out. My final question was then answered by Naj as to whether the holes in the engine bay should be plugged as further investigation showed I had one plugged and one not. Both now have new rubber plugs and no leak Hoorah.

Thanks guys, this site really does have a wealth of knowledge, although finding it can be a problem at times.


David Brough
1969 280SL Auto with A/C & 3.45 Axle

[stassenk]

David, I'm glad that the leak is sorted out. I know the feeling of wet feet in a pagoda! I must actually go and have a look if mine is still there. That might also be one of the problems.

[bpossel]

Hi David,

Glad that you were able to correct your leak issue!
If possible, maybe you can post the picture that helped you out.  Also point to the area that you are referring to in terms of the drain hole and where you drilled.  I am sure this will come up again with others...  Keeping these drain holes open is important.
Great job!
Bob  

quote:Originally posted by DavidBrough

Well it looks like the leak is finally cured with thanks to Bob Possel’s restoration photos. After I had managed to narrow it down to the bulkhead box section I used Bob’s excellent photo records to view the area on a clean body shell and noticed there were drain holes into the inner wheel arch. On my car one was fine but the other was not there at all. I had a foot well replaced about 2 years ago and the seam had been welded flush where the drain should be so I drilled a hole and about a pint of water rushed out. My final question was then answered by Naj as to whether the holes in the engine bay should be plugged as further investigation showed I had one plugged and one not. Both now have new rubber plugs and no leak Hoorah.

Thanks guys, this site really does have a wealth of knowledge, although finding it can be a problem at times.


David Brough
1969 280SL Auto with A/C & 3.45 Axle

[DavidBrough]

Managed to take a few photos of the drain holes in question as follows:-


R Side1 & 2 shows the correct drain which is a kink in the seam between the box section and footwell by the join with the inner wing

L Side1 & 2 shows the lack of a drain seam probably due to replacement of the panel and the hole I drilled to let the water out.

Thanks again for the great restoration photos Bob.



David Brough
1969 280SL Auto with A/C & 3.36 Axle



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[stassenk]

Hi David

I had the same problem yesterday evening.  The drain holes were covered with rubberising and due to that the water went through the lower drain tubes into the car. That's why all the water on my feet. Now I've got rust all over as the water wanted to come through the metal.

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