Water Leakage Into Interior

[YEOH250SL]

Hello, Every time after washing my car, water leaks into my interior. I tried to trace the source and found that it is coming in from the firewall. It looks like a pipe running through the firewall. May I know what is the purpose of the pipe? I have attached a photo. Thanks.

[YEOH250SL]

And the color of the water really concerns me. It's rusty water.

[Pawel66]

If I read the picture right, it is the drain hose responsible for draining water from the ventilation/heating air intake area. These water drains are often clogged. You need to get under the scoop and see what is happening there.

Suggest you take a look at this: https://www.sl113.org/wiki/ChassisBody/Drains#Waterdrainsinheadlightswells

Particularly section: Heater Drain (or Ventilation Drain).

Search function will also produce plenty of results.

[Kevkeller]

Your pipe is probably rusted there. Mine rusted and I’m have to weld in a new pipe. If you look in the engine bay, the other end sticks out. The pipe goes through a boxed section. It’s not easy to fix. My fire wall had rusted also so I had to make an entire replacement piece. I’m still in the middle of the repair.

If you are lucky it’ll just be the rubber hose that is leaking.

[mauro12]

This car was designed in a strange way regarding drain holes . You have to replace the rubber hoses under the dash . The best way to prevent any water inside the cabin is in my opinion , to close the blue air lever in the dash . This closes the air scoop flap you have a perfect seal to prevent any dirt or water inside .

[Harry]

The issue with closing the blue air lever is that you stop any cabin ventilation - including heating.  When everything is working properly, you shouldn't have an issue with water getting into the cabin.  That being said, cars of this era are certainly not as weather tight as later eras.  Hence the issue with rust issues we often encounter.

[Pawel66]

Well, they are certainly not so perfectly designed, but an issue of clogged water drains applies to modern cars as well, I think...

[LindesayOne]

I agree with the previous comments. I would suggest that you first lay on your back and look up at a place above your accelerator pedal. Here you will find a 150mm rubber hose (or remnants thereof) connecting the (rusty) drain pipe from the heating damper enclosure with the (rusty) drain pipe which discharges through the firewall. Best case scenario - according to my recent experience - is that the hose needs to be replaced along with new hose clamps. A simple plumbing job - for midgets. Applies to passenger side also.

John

[YEOH250SL]

Thank you guys for all the valuable information. I will try to tackle the problem this week end. Finger's crossed hoping it is just rubber hoses. My fresh air flap doesn't come with the rubber seal. It should have a seal. That's probably why water is getting in. So, do you guys shut the flap every time you wash your cars?

[Pawel66]

I do not think we do (most of us). Water coming in is no issue as long as you have these drain passages free, not clogged. If you intend to dismantle this (remove the grill of the air scoop, cover, etc.) make sure you take, e.g. a piece of wire and free the drains (shown on one of the pictures).

You will probably need also to replace the air filter (A 113 830 01 18, available at Mercedes), gasket you mentioned (A 113 831 10 98 - I see NLA at Mercedes), drain hoses and clamps and whatever else you find out. You may want to try to apply rust inhibitor if you have surface rust anywhere there.

You can see the parts here: https://www.sls-hh-shop.de/en/mercedes-230-280sl-w113/83-heater-system

The gasket is No. 12, the filter is next to it and has no number as they do not sell it (Mercedes dealers have it).

Part No. 27 is stuck on drain pipes on their engine bay ends. It is a kind of one-wat valve for drain water. Some say it is only used on drivers side and it would be too close to exhaust on passenger's side. I see 2pcs required for a car on parts list - for both sides. Horrifyingly expensive at Mercedes for some reason, buy it elsewhere.

[sandcrab59]

That looks like the drain hose from the air scoop.
I replaced my hoses.
But make sure the lines are clear.
Tom M

[sandcrab59]

I forgot, it could be the metal at the fire wall is rusted.
Like someone stated above you have to weld in a new short pipe into the firewall.
Tom M