How to ensure that trunk is watertight?

Papa Popov · 01-16-2022, 01:17 AM

So a couple years back we had a big snowstorm, and shortly thereafter my TPMS stopped working. Turned out that water had gotten into the RDC and fried it. Since then I've installed LCI tail lights (which obviously had new seals) and haven't had any issue since (knock on wood). However I'm super paranoid because I have a Bavsound amp that's NLA just chillin' at the the bottom of the trunk and I want to ensure that it doesn't get fried. I've been thinking about throwing it in a big ziplock and raising it up a few inches as a last line of defense, but what seals or parts should I replace to ensure that no water gets in?

iamroddy · 01-16-2022, 12:21 PM

I would have a good look first. Pull out the trim/panels inside the trunk, and take a friend with you to the coin-op car wash. Get in the car, drop the rear seat backs, and watch for water. Have friend spray high pressure around trunk lid, tail lights, rear inner fenders, and all the way around inside the bottom of the bumper cover. If there's a leak, that should show you where it is.

BMWCCA1 · 01-16-2022, 01:34 PM

In my wife's 2008 (RIP) I think water was entering the compartment under the carpet below the taillight somewhere along the frame rail and getting in the styrofoam holder for the TPM control. I never found a spot but I did drill holes in all the compartments in the styrofoam and then used one of the plastic plugs in the bottom of the body to insert a tube to vent any water. Never had another issue with it. I don't see the same issue in my 2013 but it would be just like BMW to never have fixed the problem.

01-16-2022, 01:17 AM	#1
Papa Popov Lieutenant 315 Rep 474 Posts Drives: 2009 128i 6MT Join Date: Mar 2020 Location: SoCal iTrader: (0) Garage List 2009 BMW 128i Coupe [0.00]	How to ensure that trunk is watertight? So a couple years back we had a big snowstorm, and shortly thereafter my TPMS stopped working. Turned out that water had gotten into the RDC and fried it. Since then I've installed LCI tail lights (which obviously had new seals) and haven't had any issue since (knock on wood). However I'm super paranoid because I have a Bavsound amp that's NLA just chillin' at the the bottom of the trunk and I want to ensure that it doesn't get fried. I've been thinking about throwing it in a big ziplock and raising it up a few inches as a last line of defense, but what seals or parts should I replace to ensure that no water gets in?
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01-16-2022, 12:21 PM	#2
iamroddy Private First Class 86 Rep 117 Posts Drives: 128i Join Date: Sep 2020 Location: 613 iTrader: (0)	I would have a good look first. Pull out the trim/panels inside the trunk, and take a friend with you to the coin-op car wash. Get in the car, drop the rear seat backs, and watch for water. Have friend spray high pressure around trunk lid, tail lights, rear inner fenders, and all the way around inside the bottom of the bumper cover. If there's a leak, that should show you where it is.
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01-16-2022, 01:34 PM	#3
BMWCCA1 BMW Owner Since 1971 2257 Rep 1,407 Posts Drives: 1964 700 Sport Cabriolet Join Date: Apr 2014 Location: Central Virginia iTrader: (2) Garage List 2013 BMW 128i [10.00]	In my wife's 2008 (RIP) I think water was entering the compartment under the carpet below the taillight somewhere along the frame rail and getting in the styrofoam holder for the TPM control. I never found a spot but I did drill holes in all the compartments in the styrofoam and then used one of the plastic plugs in the bottom of the body to insert a tube to vent any water. Never had another issue with it. I don't see the same issue in my 2013 but it would be just like BMW to never have fixed the problem.
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