finding source of rain leak into cabin

[Mashford]

Hello Folks,
I hope someone might help me identify and fix the source of this rain water leak into the cabin of my 87 535is. I found the entry point (I think) at a hole (part of design, not a puncture or rust caused hole) in the sheet metal behind the back seat rest, which I removed in the course of fixing speakers on the rear shelf. See the circled area in this photo:

This is looking back towards the rear windshield, passenger side, with my back against the backside of the front passenger seat. The red circle is around the hole where I see water coming in, through the foam padding that is poking out.

The water runs down the interior sheet metal of the rear wheel well and from there and enters this hole to finally pool under the carpet on the floor of the rear passenger side seating area. This photo shows from above where the trickle of water flows down and into the hole:


It seems like the water is entering through the air vent, because it is located directly across from (on the outside of car) and above where the leak enters as shown in the first photo. I tried to pull the vent cover in the photo, and it looks like some kind of glue or sealant is damaged (I did not want to pull further and completely detach when I saw the seal). See location (behind the cover) of what looks like a break in a seal:


Has anyone had an issue like this before? I am searching for more information on the vents and covers and seals, if anybody knows more.

Thank you for any comments, suggestions, further resources!!!

[jyl]

I’ve not had the issue myself, but have read that if any of the circular things that the vent cover attaches to are missing, water can get into the body through the pillar. I think you should put a hose on the vent and see if water comes into the car.

[Ordnator]

There are some plastic grommets that the C-pillar cover attaches with that will let in water if they are perished or missing.

https://www.realoem.com/bmw/photos/51141852899

https://www.realoem.com/bmw/photos/51131870459

Exterior trim / grill

No. Description Supp. Qty From Up To Part Number Price Notes

04 Grommet 2 51141852899 $1.84
05 Insert 10X7 8 51131870459 $0.38

Best regards,

Mick

[Mike W.]

I had those vent covers on and off a couple of times with no issues, but many have had the grommets fail and cause a leak.

[Mashford]

Thanks everyone! I will replace the grommets and test before reassembling. Hopefully that does the trick.

[Mashford]

I pulled the vent cover on the c-pillar and see broken grommets to replace. Thank you for the reference to the parts. See this photo: Update and question here:



Any ideas about this seal (like a double-sided tape) that is torn?

See here:



And zoomed in a bit here:



Thanks.

[Mike W.]

I don't recall any double faced tape like that, but given the condition your seals/grommets were in, which is pretty nonexistant, I'm guessing that was to hold the vent cover on since the grommets wouldn't have.

[Ordnator]

Looks like a silicone "bodge it and scarper" fix

Best regards,

Mick

[Mashford]

"bodge it and scarper"

translation please, for us outside of Nova Scotia (?)

[Ordnator]

UK slang for doing a gash (bad) job and disappearing with the cash

Best regards,

Mick

[Mike W.]

I couldn't have translated it word for word, but I knew what he was saying. But really, once the word silicone appears the meaning suddenly becomes clear.

[Mashford]

Well, I replaced the grommets and put soft rubber washers around them to try to re-create the original seal for the vent cover... and it is still leaking in the same spot. It seems to be coming in at a high point because there is some staining in the interior headliner and I could also feel dampness in the foam padding behind the liner during the last event. With the rear seat still off, I have access to the liner edge and could -- or? -- investigate further by pulling off the headliner inside the cabin and investigating from inside (and the foam behind it?). It just seems like it would be something very difficult to put back together again in a way that looks as good as it is now. In addition, the headliner is so old and delicate, so I fear I will tear it if I go at it this way. But what else can I do? Any ideas? I can send photos, if helpful.

Part of the problem is that it is very difficult to diagnose. Maybe I could seal the entire vent from the outside and douse with the house to be sure, first of all, that it isn't leaking in mysteriously from some other source (e.g. the door seal? the trunk seal?).

Thank you!

[Mike W.]

With the headliner at 35 years of age I would be very reluctant to try a partial removal and reinstallation.

I would be surprised, but any chance of it coming in thru the rear windshield seal? How soft and pliable is it? I would try my favorite windshield sealer, 3M glazing and bedding just under the upper lip where it's against the body before I dug in any more, but it's a long shot. Now assuming it is the side vent, I would try either the aforementioned 3M sealant, or butyl tape, just a little bit of it as a gasket at the grommets. Speaking of the grommets, I wonder if they're the same as original and if water might be leaking thru them assuming they're the split kind.

Cancel cancel cancel, I know what it is. There is a closed end socket that is supposed to be there but isn't. The vent mounting tab goes into it, but not thru it, so it stays sealed. #5 https://www.realoem.com/bmw/enUS/showpa ... Id=51_0817

[Mashford]

Cancel cancel cancel, I know what it is. There is a closed end socket that is supposed to be there but isn't. The vent mounting tab goes into it, but not thru it, so it stays sealed. #5 https://www.realoem.com/bmw/enUS/showpa ... Id=51_0817

That might be it! Thanks. It looks like I used a standard grommet at the top, not the special one. I will order -- looks like Pelican parts has some. Fingers crossed and thanks again.

[Mike W.]

Looking at your car, it appears all but the very bottom one have oval holes, the bottom being round.

[Mashford]

Looking at your car, it appears all but the very bottom one have oval holes, the bottom being round.

Yes, to be honest, I was a bit confused by the differences. I did put an oval grommet on the top post and did find a round one for the bottom post. So, ordering some more with the part number (it all looks different the schematics) to double check the fit. I honestly think at this point there is a 50-50 chance it is the grommet. But worth a try. Then I am going to try -- if that fails -- and seal the whole vent and work the hose to see what happens point-to-point. Back soon.

[Mashford]

Hey Folks,

Well, I don't think it was/is the grommet. I did have good (new) grommet at the top, and all the way down. See the photo here:



The bottom one is different than the rest, and I have the right one for that, too (same as used on roundels).

So, could it be the foam rubber seal that you can see here that runs along the vent cover where the grommets are? It was coming loose and I glued it down, but it has lost a lot of its suppleness overall. I also put in the black rubber washers myself as a DIY replacement for very thin rubber washers that were there when I first removed it. They were fairly deteriorated, so I threw away with the old grommets. But perhaps my DIY replacements are too thick and creating a gap?

So, working on the theory of either its (1) that foam rubber strip needs to be replaced/augmented and/or (2) my DIY rubber washers are creating a gap.

I welcome your thoughts and suggestions!

[Mashford]

Problem solved. It was the grommets. But for all those “learn as you go” folks like me out there — put the grommets on the car, not the little posts on the vent cover. Tap the grommets on to ensure a seal and until they “click-in” on the car’s body metal. THEN push the vent cover posts into the car (holes with grommets you just installed).

I made the idiot mistake of putting grommets on the posts first and then trying to push the vent posts into holes on body of car. The grommets won’t seal against the car if you do it incorrectly.

I tested with a hose to check.

[Ordnator]

Thank you for following up with the final piece to the puzzle.

It is just a small installation detail, but is essential for the grommet's to work.

Brilliant, here's to many more miles of dry cabin motoring

Best regards,

Mick

[Mashford]

Thank you for following up with the final piece to the puzzle.

It is just a small installation detail, but is essential for the grommet's to work.

Brilliant, here's to many more miles of dry cabin motoring

Best regards,

Mick

Cheers, Mick! This forum is invaluable!

[vb9594]

Hey Mashford- can you confirm how many of those grommets you ended up buying? And that you bought #5 from the diagram, correct? Thanks very much- chasing down this exact problem, too!

Brian

[Mashford]

Hey Mashford- can you confirm how many of those grommets you ended up buying? And that you bought #5 from the diagram, correct? Thanks very much- chasing down this exact problem, too!

Brian

From top to bottom, there are five grommets. The first 4 are oval shaped. The last and bottom one is round and was identified in RealOEM as a grommet for roundel. I can get part numbers, but let me know if that answers your question. You can see pictures of the grommets at Pelican Parts and/or FCPEuro Parts. It’s pretty clear when you see pictures (oval vs round).

[vb9594]

Awesome- that gives me what I need. Appreciate the help!

[Mashford]

Awesome- that gives me what I need. Appreciate the help!

Oh no! Big rainstorm yesterday and is still leaking!! Ugh. Apparently my hose test was not realistic enough.

[Mashford]

I am really bummed that the leak is still there. If anyone has further advice, please let me know. I am going to DM vb9594 to see if they had any final success.

[vb9594]

Hey Mashford- so far so good...but we haven't had any really heavy rain yet, so I'll keep checking and let you know!

[sixseries]

As someone who spent hours tracking down and finally remediating a water leak in the firewall, my best advice is to spend more time diagnosing the actual leak spot. Have someone else just absolutely hose down the area where you think its leaking. A hose should put out much more water than a rain storm. I wasted a lot of time because I did not spend enough time diagnosing the actual leak.

[Fedaykin528e]

I have never had the headliner off of my cars, so really don't know what is going on in the area the sunroof retracts into. But, I am wondering if your sunroof drains might be backing up rearwards. Maybe try masking taping off the sunroof on the roof for the next rainstorm? Other than that, Mike might be onto something with the rear glass seal, especially at the top.

[Mashford]

As someone who spent hours tracking down and finally remediating a water leak in the firewall, my best advice is to spend more time diagnosing the actual leak spot. Have someone else just absolutely hose down the area where you think its leaking. A hose should put out much more water than a rain storm. I wasted a lot of time because I did not spend enough time diagnosing the actual leak.

Thanks -- will do that,

[Mashford]

I have never had the headliner off of my cars, so really don't know what is going on in the area the sunroof retracts into. But, I am wondering if your sunroof drains might be backing up rearwards. Maybe try masking taping off the sunroof on the roof for the next rainstorm? Other than that, Mike might be onto something with the rear glass seal, especially at the top.

Thanks -- will do more diagnostics, including glass.

[Mashford]

Finally got around to the full on hose test. After 5-10 minutes dousing the back left vent and rear windshield, and getting no results, I non-chalantly put the spray on the sunroof and nearly flooded the foot zone of rear passenger side... it was a small stream of water into the car. So, I am pretty sure sunroof leak is the culptrit... now for the fix!

[Mashford]

FIXED (for now)!!!

I ran some refrigerator water hose/tubing through the passenger-side rear drain hole/tube from above and below. It never made it around an apparent curve in there, but by jiggling and shoving/pulling, a bunch of organic detritus (leaf remnants, muddy sludge) flowed out and the drain subsequently flowed. Have not had a full on rain dump on the car yet, but it worked with the hose test. Cheers.

[BMWCCA2]

We generally used monofilament line, like weed-eater. Anything stronger can dislodge the drain tube and it's small enough to get around many restrictions. Good on you for staying with it!

[Mashford]

We generally used monofilament line, like weed-eater. Anything stronger can dislodge the drain tube and it's small enough to get around many restrictions. Good on you for staying with it!

I tried the weed-whacker line I have at home and it was not sturdy enough. Neither the monofilament nor the refrigerator line would pass through drain tube entirely. I don't know if that is because of a bend in the drain that may have an edge which catches, or because of the blockage, but I tried not to be too aggressive either way. Ultimately, the rigidity of the refrigerator line is what worked (my monofilament was too flexible and could not push against it to make a dent in the blockage).

[sixseries]

FIXED (for now)!!!

I ran some refrigerator water hose/tubing through the passenger-side rear drain hole/tube from above and below. It never made it around an apparent curve in there, but by jiggling and shoving/pulling, a bunch of organic detritus (leaf remnants, muddy sludge) flowed out and the drain subsequently flowed. Have not had a full on rain dump on the car yet, but it worked with the hose test. Cheers.

Glad you found the leak!

[jyl]

Probably not your issue, but I recently learned that there is a gutter under the trailing edge of the sunroof, and if there is not then water will drip on your neck. My gutter was missing. Actually, it was detached from the sunroof and hiding all the way at the back of the roof cavity.

I slid it forward with a magnet stick (that you use to retrieve a lost nut) and figure out how to reattach it to the sunroof so that it slides back and forth with the sunroof.

I also learned that the sunroof “fingers” are supposed to have little bushings, and with those missing the sunroof is very fiddly. I pulled those bushings off a parts car and will press them on eventually.

I wish I had a tin top, honestly.