Solution: Boot/Trunk & Spoiler leaking

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TimU
Posts: 280
Joined: Tue Dec 14, 2021 2:16 am
Location: Sydney

Solution: Boot/Trunk & Spoiler leaking

Post by TimU »

A tale as old as the hills - Water ingress into the trunk area every time it rained or I washed the car.

Bottom line up front - Water sources were:
  1. Antenna grommet
  2. Boot lid seal
  3. Spoiler bolt holes
Breakdown of repairs

1. Antenna Grommet
The grommets are No Longer Available, but a 1" rubber blanking grommet is the perfect alternative.
Preparation and installation is documented here: viewtopic.php?f=5&t=32796&p=233475#p233521

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Last edited by TimU on Thu Jan 20, 2022 1:52 pm, edited 1 time in total.
04/1986 635csi Euro spec
Australian Delivered, RHD
TimU
Posts: 280
Joined: Tue Dec 14, 2021 2:16 am
Location: Sydney

Re: Solution: Boot/Trunk & Spoiler leaking - 2. Boot lid seal repairs

Post by TimU »

2. Boot lid seal repairs

My rubber gasket boot seal was in reasonable condition, but the glue/sealant had degraded which allowing water to flow under the seal, over the metal lip and into the boot.

I took my boot lid off for this work to give me plenty of room to work.
Undo 4 bolts at the hinges and disconnect the boot lid light connection at the left hinge.
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Old and crusty glue under the seal. This needs to come off!
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A combination of Acetone, Contact Cleaner & Elbow Grease did the job nicely.
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All clean.
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Paint had worn thin over the years. Some surface rust in the channel.
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Taped it off and hit it with a 2-in-1 primer and metal paint.
Not a perfect match, but close enough. It's all underneath the boot seal anyway.
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Ran a bead of translucent silicone sealant around the outside edge of the gasket lip.
(Missed a photo on the car unfortunately, too eager to install the rubber)
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Install the rubber again and let it cure as per the instructions.
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After the silicone drys, test it out by gently pouring water into the top channel at various points, allowing it to run across and down to the ground.
Check for leaks around the seal corners and inside the boot floor below the lights.

Success for me here!
Last edited by TimU on Thu Jan 20, 2022 1:50 pm, edited 3 times in total.
04/1986 635csi Euro spec
Australian Delivered, RHD
TimU
Posts: 280
Joined: Tue Dec 14, 2021 2:16 am
Location: Sydney

Re: Solution: Boot/Trunk & Spoiler leaking - 3. Spoiler bolt holes

Post by TimU »

3. Spoiler bolt holes

Water was also leaking into the skin of the boot lid via the spoiler bolt holes.
I could hear water sloshing around inside the lid as I raised it up!

This was a new development after some rust repairs a few weeks back, so it seems like they didn't reseal the bolt holes properly.

Spoiler Off
I took the spoiler off (4x 10mm bolts and 2 screws under the boot lid) and taped over the holes with some bumper strip tape.
Bumper Strip Tape from AliExpress.

I left the car like this for a few days in the rain to see if there were any other water ingress locations I'd missed.
Thankfully none - The boot was dry after some heavy rain.

I added a long strip of tape along the spoiler-line with the hope of creating another barrier or water divergent, but in hindsight I think was unnecessary.
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I sliced a small cross in the tape to allow the bolt to slide in to the holes.
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Silicone blobs (same stuff used above) around the 4 bolts on the spoiler.
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Carefully lined up the bolts to the holes and reattached the spoiler.
A bit of silicone squeezed through the hole - Good!
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Nuts and rubber hat washers back on.
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Finished. Let it cure before testing.
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Last edited by TimU on Thu Jan 20, 2022 1:49 pm, edited 3 times in total.
04/1986 635csi Euro spec
Australian Delivered, RHD
User avatar
Sbeaud
Posts: 279
Joined: Fri Jan 04, 2019 9:38 pm
Location: Okahumpka, Florida USA

Re: Solution: Boot/Trunk & Spoiler leaking

Post by Sbeaud »

Nice work - thanks for the pictures.

One comment though - I hope the silicone does not give you any issues. I'd be concerned about the temperature and other environmental extremes that automotive components experience. Really hope you don't experience any problems!

Scott Beaudry
1988 M6
TimU
Posts: 280
Joined: Tue Dec 14, 2021 2:16 am
Location: Sydney

Re: Solution: Boot/Trunk & Spoiler leaking

Post by TimU »

Thanks.
Sbeaud wrote: Thu Jan 20, 2022 1:35 pm I hope the silicone does not give you any issues. I'd be concerned about the temperature and other environmental extremes that automotive components experience. Really hope you don't experience any problems!
Yeah I considered that and spent way too long in the Hardware store sealants aisle looking for the right product. ](*,)

But this stuff seems like a good fit:
* indoor & outdoor use,
* as a wet area sealant (high moisture areas),
* temperature range -40C to +150C,
* mould resistant
* high movement areas, 25% "stretchiness"

That area of the boot is not a high temp or high movement area, so I think it should be alright.
Should be easy enough to rip out, clean-up and try again with something else if it doesn't work.
Finger's crossed!
04/1986 635csi Euro spec
Australian Delivered, RHD
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