finding source of rain leak into cabin

E28 technical advice asked and given! Troubleshooting, modifications and more.
vb9594
Posts: 33
Joined: Sep 25, 2009 1:16 PM
Location: Leominster, MA

Re: finding source of rain leak into cabin

Post by 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
Posts: 1326
Joined: Jan 25, 2008 1:17 AM
Location: Portland, OR

Re: finding source of rain leak into cabin

Post by 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
Posts: 685
Joined: Apr 03, 2008 2:21 AM
Location: Brooklyn

Re: finding source of rain leak into cabin

Post by 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
Posts: 518
Joined: Jun 19, 2006 2:15 PM
Location: Takoma Park, MD

Re: finding source of rain leak into cabin

Post by Mashford »

sixseries wrote: May 16, 2022 1:40 PM 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
Posts: 518
Joined: Jun 19, 2006 2:15 PM
Location: Takoma Park, MD

Re: finding source of rain leak into cabin

Post by Mashford »

Fedaykin528e wrote: May 16, 2022 5:11 PM 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
Posts: 518
Joined: Jun 19, 2006 2:15 PM
Location: Takoma Park, MD

Re: finding source of rain leak into cabin

Post by 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
Posts: 518
Joined: Jun 19, 2006 2:15 PM
Location: Takoma Park, MD

Re: finding source of rain leak into cabin

Post by 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
Posts: 4060
Joined: Feb 12, 2006 12:00 PM
Location: Central Virginia

Re: finding source of rain leak into cabin

Post by 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
Posts: 518
Joined: Jun 19, 2006 2:15 PM
Location: Takoma Park, MD

Re: finding source of rain leak into cabin

Post by Mashford »

BMWCCA2 wrote: Jun 29, 2022 9:27 PM 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
Posts: 1326
Joined: Jan 25, 2008 1:17 AM
Location: Portland, OR

Re: finding source of rain leak into cabin

Post by sixseries »

Mashford wrote: Jun 29, 2022 10:55 AM 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
Posts: 138
Joined: Jun 02, 2016 8:59 PM
Location: Oregon

Re: finding source of rain leak into cabin

Post by 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.
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