Water ingress through fresh air scoop ? Expert opinion sought!

[Sleek Lemur]

Here's today's post ! 

I've owned my car for 11 years and it has been maintained by a couple of specialists. The first lot in London, I think have closed for business, the second has retired. The second guy was brilliant at keeping the car running well. Lovely fellow as well. However, unless you're VERY lucky, your specialist may not perform the Frech air intake service at outlined in our Service and Maintenance manual (job no. 7815).

https://www.sl113.org/wiki/ChassisBody/Drains#HeaterDrain

I now have the time and facilities to look after the car myself and, performing this task found that, although the drain holes were not blocked, there was a 2 inch rust hole in the airbox, as the original caulking was very loose.

However I was surprised to see the evidence of the water ingress and would love to hear from anyone with more experience than me. Photos attached.

"Driver's Side" (car is RHD). It seems obvious where the water has got in, through the airbox drain, except it wasn't blocked and the rubber pipe is ok. I did notice the clamps weren't very tight. However, Note that blue circular hole
above and to the right. Before I taped it up, it was a 25mm hole straight into the engine compartment and there was evidence of water ingress. I will buy a grommet and I assume this hole was used for LHD cars.

"Passenger Side" was even more intriguing ! When I took out the screws holding the under-dash panel, a good half-pint of clean water poured into the footwell ! It seems that this was water that got trapped in the box section to the rear and below the coolant expansion tank.

Take a look at the final picture "Bulkhead". You can see a hole below where the screen wash tube enters the bulkhead. I think this should have a grommet as well, but a) what's the purpose of the hole and b) where can I drain any traded water? The box section seems completely sealed.

There is a happy ending....the driver's side floor is ok, though the material under the carpet was rotten and the caulking old and loose and the passenger side was in great condition.

So, that's it. I think I have escaped pretty well, but his whole area looks like a real minefield. Would love to hear the experts' comments!

Thanks as always ! What a superb club this is !

[Sleek Lemur]

With Pics this time!

[Pawel66]

I am not very experienced in this, others will come with much better advise, but about water pouring from under dash panel on your passenger side as well as water in the place under where washer hose and bonnet release are going through the firewall I had one and the same reason: lack of 2 grommets/seals for washer hose going twice through the fire wall (see link). Water was just floating down the washer hose from air scoop. Maybe it is this. I think the hole you mention is a drain hole. Water gets to that place between the bonnet and the wing edge as well (no gutters along the wing edge).

 https://www.sl113.org/forums/index.php?topic=27755.0

The two other places - I am not sure but maybe those 2 steel drain pipes that go through firewall to engine bay need to be sealed on engine bay side. That is, if you say that they or their rubber vents were not clogged.

There are several posts on water leakages unde dash (drain hoses, wipers shafts, air flap open inheavy rain, windshield seal). I sent someone under dash and I poured water on the windshield from the bucket - then you may see where it is comig from.

[Sleek Lemur]

Thanks, Pawel. It seems strange to me that there is a random hole allowing water to enter the box section, with no exit. I don't get the purpose of that hole below the washer jet. Anyway, like you suggest, I will get some grommets. Strange...

That said, I will do the fresh air intake service annually !

On too the soft top compartment drains next !

[rutger kohler]

Hi, I have put a post up several days ago asking about how water gets into the box section you are talking about, in my car (RHD). I have had no reply which could fix this problem, and have just seen your post which sounds a similar problem.

I assume an earlier owner had drilled a 3mm hole up into the bottom of the box section, you talk about, past the steering column and about 40mm from where the box section meets the gearbox tunnel, presumably to let water drain out, although I have never had a cover plate under the right hand side of the dashboard and it may be where the back of this normally secures by screws?

I am putting the car back together after a bare body resto and need to sort this problem before I put the carpet back in the car.  The hole only leaks when it rains.

I have had the ventilation box completely stripped out and tested the drain holes/drain pipes and made sure that the box itself doesn't have any leaks. I have also poured water into the corner of the enginebay and made sure the little drain at the underside corner of the mudgard (fender) is also working.  I have also sprayed water along the outer ledge formed by the top of the box section, on the front of the firewall and can't get it to leak.

Attached is photo showing the leaking hole.

Really need to sort this problem

[Pawel66]

Which random hole do you mean? The one from your picture next to the firewall, below the washer hose and bonnet cable? This hole allows water out, not it. There is no gutter around the bonnet and water falls on the flat wheel house/fender area under the expamsion tank (or brake booster on LHD).

What do you mean by "the box section"? If you mean the fresh air box under scoop - there are two drain holes to let water drain from the air scoop, one on passenger, one on driver's side. Each of them has a hose under dash, two clamps, steel pipe that goes through firewall and vents (on one or both) in the engine bay. The steel pipes are on your pictures if I read them correctly. I see one hose removed on your passenger side picture, so I see just the steel pipe. I thought you removed this hose. If this hose was not there - this is the source of a true flood! On the driver's side I see you have a hose on, but it looks like water is coming in around the steel pipe from the engine bay side. Or the hose/clamp are not tight or water is floating down that hose from the upper hose connection and creates the stains we see on the picture.

Making sure that these two drain passages from the air box are not clogged is one of the critical maintenance points. See Technical Manual /Chassis and Body/Water Drains.

Then there are two holes for the washer hose I described.

So I am not sure which hole seems random. And if by "the box" you mean the fresh air box under scoop - there are two serious exits I just described. You may do the search "water drain" or "drain holes". Unfortunately some of the index links do not work, but one can figure out the main water drain topics.

You say: "do not get the purpose of the hole under the washer jet" - which hole do you mean?

[mbzse]

.../...Making sure that these two drain passages from the air box are not clogged is one of the critical maintenance points.../...

Also the multiple small drains all around the W113 body must be open to enable water to escape.
See: https://www.sl113.org/forums/index.php?topic=26785.msg191656#msg191656
Also here:
https://www.sl113.org/forums/index.php?topic=375.msg39715#msg39715

[rutger kohler]

Thanks Hans, I looked this post up (Don Carron 2003) I think and below are his comments that relate to the box section (firewall cross member in his post):

"The firewall cross member along with the front bumper cross member really don't have drilled holes at all. This is more like a groove in the stamping process and leaves a space where water can run out. These small grooves or ridges are in a lot of different places and most of them are plugged solid with dirt. You can use a wire or screw driver to clean them but watch that you don't remove any paint and exspose bare metal. You can dip a pipe cleaner in some paint and swab the hole which might help a bit."

So Don (or others) where are the small grooves or ridges located please, can't wait to clean them out?

[Pawel66]

Yes, thank you Hans.

I tried to include some detailed references, but the links did not work. My understanding is:
- two drains from the air box
- S-frames front support
- front cross member
- rear cross member
- flat areas undder expansion tank and brake booster (disputes held, refer to other posts and "Search")
- soft top compartment both sides
- headlight wells
- practically all or most hollow elements
- outside rear view mirrors

This is what I collected form the forum or found myself, there is probably more.

[Sleek Lemur]

Thanks to all contributors.

The air scoop issues I get and it's all very straightforward.

what I still don't understand is the purpose of the hole in the horizontal panel just in front of the bulkhead where the windscreen washer enters. I can put a grommet in (there is one on the opposite side of the car). Very interested to read of the hole a previous owner had drilled under this box section in your car, Rutger. Seems like a good idea, however am cautious to drill a hole where Mercedes didn't, as there is just the smallest chance that they knew what they were doing, whereas I am clueless!

[Pawel66]

what I still don't understand is the purpose of the hole in the horizontal panel just in front of the bulkhead where the windscreen washer enters.

This is a drain hole. This has been discussed here as some of the fellow members had it plugged too.

[rutger kohler]

Hi, I wouldn't drill a hole, can't someone show us where the drain runnels, in the box section, are that Don Carron talked about? If these are identified and cleaned out there is no need to drill holes etc.  Perhaps a better question is, how does water get into the box section in the first place?

[Pawel66]

Rutger,

If by "box section" you mean the fresh air box under the air scoop, under the air flap between the bonnet and the windshield - yes, no need to drill holes.

Picture of drain: https://www.sl113.org/wiki/ChassisBody/Drains

Shows one side. The other is on the other side. You can also look up under dash. You will see both on passenger and driver sides tubes/pipes coming down from under windshield area, from the air box, with rubber hoses that should be on them (with clamps). Then rubber hoses go down to a piece of a steel pipe going from the hose (also with clamp) to toeboard and out to engine bay.

If you look at the firewall from the engine bay side - on LHD left hand one is down there a bit towards the center from brake booster, but lower. It may have ball shape vent stuck on it. On the right hand side the pipe is coming out where exhaust pipe meets the firewall before it goes down. This one may not have the ball shaped vent, it can look just like a piece of pipe sticking out of the firewall.

If you stick some piece of copper wire up those pipes in the engine bay, they should come out in the air box.

More pictures are there if you search "water drains".

Water gets there through the air scoop and air flap, which is quite natural, I think.

[Sleek Lemur]

Hi Pawel, we're not talking about the fresh air box. The water is getting in to a box section in the bulkhead through a hole in the horizontal section under the expansion tank, Yet there seems to be no exit for this water. It only became apparent to me after I clumsily refilled the coolant and spilled some, which went down the hole. I think there should be  a grommet in the hole, but what is the hole for ?

I attach the picture again.

[Pawel66]

Ok, I see.

You learn all the time. I did some searches and I see two schools - one is saying drains, the other says - technological openings for hollow section undercoating that should be plugged.

I was convinced these are drain holes, but I am not sure anymore.

A quote on one school (there are many):

"There are more drain holes in the engine bay.  In the corners where the firewall & fenders come together there is a flat area (under brake booster & under radiator expansion tank on LHD cars).  There should be an opening that lets water run down into the front wheel wells.  Also, where the front frame rails come down and meet some other parts (I forget what), there are two more drain holes.  These are under the battery and air filter housing.  They can be cleaned with a small screwdriver or similar device."

And a couple of links for the other school (including one from rutger):

https://www.sl113.org/forums/index.php?topic=489.msg2083#msg2083

https://www.sl113.org/forums/index.php?topic=22082.msg157713#msg157713


And a couple of pictures attached.

I do not know any more. In this case I would spray in some wax in and plug them. We need more experienced opinion than mine, I do not know enough.

[mbzse]

.../...water is getting in to a box section in the bulkhead through a hole in the horizontal section under the expansion tank.../...

Put a rubber plug in that hole which is visble in your picture! Water must not enter there.

Any condensation etc from inside that large box section is ment to be drained via drain openings (in the front wheel well)
Make sure these are open (by means of a dowel or screw driver etc, as explained)

Read more on drain openings in the bodywork of our W113 cars in this posting:
https://www.sl113.org/forums/index.php?topic=375.msg39715#msg39715

[Edit: picture added]

[Pawel66]

Hans, you mean the openings in the wheel well as on your picture below, the upper right circle? Or these are somewhere else?

That would mean that the holes inside in that section are just vent holes?

[mbzse]

The openings are reasonably obvious in the wheel well.
 They are indicated in the accompanying picture of mine

[Pawel66]

Thank you! Will have to find them on the car - I want to chase that...

[rutger kohler]

Hi, I beg to differ, if you pour water down into the corner of the firewall, and the mudgard/fender, behind the brake booster you will see water come out the drain you are indicating.

[mbzse]

.../....if you pour water down into the corner of the firewall, and the mudgard/fender, behind the brake booster you will see water come out the drain.../...

It will come at the drain marked "A" in Pawels top picture "drains wheel arch" (reply #15)

[Sleek Lemur]

Thank you Pawel, MBSE and Rutger !

And Pawel, those photos show me exactly what I need. The "additional drains" in your first photo are what I'm referring to and the exit "A" in your other pic is blocked by (paradoxically!) rust protector underseal, meaning that when I unscrewed the trim in the LH footwell, the water I had spilled when filing the expansion tank (RHD car) ran out. The RH "additional drain" has a grommet, so in fact, these don't seem to be drains at all (just as Pawel suggests).

Again, thank you, thank you, thank you all. Imagine the potential damage if I had not been able t source this wisdom!

[mauro12]

Hello guys , I just replaced the rubber hoses under the dash because I had the same problem about water leaks. My question is: would be better to close the air scoop during heavy rain or during car wash? Are there any other chances that water can come on the floors?

[StevenF]

I had the same issue very recently.  I removed the air scoop and filter, etc and simply took a wire hanger and ran it through the left and right drain opening until everything cleared out. Look for this https://www.sls-hh-shop.de/main/de/mercedes-230-280sl-w113/54-elektrische-ausstattung-karosserie/54-d-gummituellen/gummikugelventil-entspr-110-831-0132-p-7036
inside your engine bay on and remove it to clean (flush it) or replace it.  On the other side (the driverside) you will note a metal drain that the wire hanger should be coming through.  If you see the hanger on both sides then you did it right. 
If memory serves me, you may have to adjust the levers inside to make removal of the filter easier.

Be careful when removing the screws for the air scoop there are a few "inside" so after removing the external ones, dont pull on it until the internal screws are removed.

[mbzse]

.../...My question is: would be better to close the air scoop during heavy rain or during car wash?.../...

Does not help closing flap (scoop); the water is already within the bodywork of your car.
If you want to, you could cover the entire opening in front of the windscreen while you wash your car.
Note: If the drains are okay, this is not needed