Rust prevention behind taillights, etc.. waterproofing..

MomoJeep

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City
Seattle
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WA
I had to remove a taillight and found the paint was beginning to blister a bit behind it. Water gets trapped in there. I coated the space between taillight and sheet metal with a little grease. But I'm wondering (a) will the grease damage the paint over time and (b) is there a better way to protect places like this?

Another example is that I have a roof rack that mounts using little plates that mount in the front over the top of the windshield hinges. This creates another tight gap that water can get trapped in. Even running a bead of sealant over the top probably wouldn't be enough, since driving in the rain could force water in the sides. I wouldn't want a solid slab of sealant in there, because then I don't think it'd ever be removable!

Any ideas?
 

Kim Dawson

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City
Molalla
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Or
Might try filling the gap with some caulking. If you want it to come apart easier, maybe use the caulk strips that never seem to ever harden.
 

Randyzzz

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I used a closed cell EVA foam on Copper behind the lights. Wasn’t able to test it longer than a year but it seemed to hold up well. My biggest fear is that the foam will trap water and compound problems. I’ve got a piece of it crushed between 2 washers on a bolt, soaking in a cup of water. I’ll pull it apart after a couple weeks and see how far the water has intruded.
 

MomoJeep

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City
Seattle
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WA
I used a closed cell EVA foam on Copper behind the lights. Wasn’t able to test it longer than a year but it seemed to hold up well. My biggest fear is that the foam will trap water and compound problems. I’ve got a piece of it crushed between 2 washers on a bolt, soaking in a cup of water. I’ll pull it apart after a couple weeks and see how far the water has intruded.
That’s a cool experiment you’re doing! I’d love to see a second version but using salt water!

Here they say oil/grease won’t damage the paint: https://itstillruns.com/oil-off-car-paint-5611938.html

somebody also suggested wax. Would wax be better than grease?

then there’s bedding compound. It’s a little bit sticky but doesn’t dry and it’s not really an adhesive. This is what they use around windshields. If this assembly is not too big of a concern this might be a good way to go, and it would still allow this assembly better than caulking or silicone.
 

MomoJeep

Basic User
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City
Seattle
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WA
I used a closed cell EVA foam on Copper behind the lights. Wasn’t able to test it longer than a year but it seemed to hold up well. My biggest fear is that the foam will trap water and compound problems. I’ve got a piece of it crushed between 2 washers on a bolt, soaking in a cup of water. I’ll pull it apart after a couple weeks and see how far the water has intruded.
What about this stuff?
 

rubclt

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Charlotte
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Any photos of your rust area? I would think a rust converter might be good with a top coat to protect from UV rays
 

jammer1

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Maple Hts.
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Oh
If you use chalk, don't chalk all 4 sides, chalk the top and 2 sides, leave bottom open. If not you will trap any water that gets in and it will rot out faster. Always leave a way for the water to escape. Grease is better than wax, Rust pores are too large for the wax to bridge and will break down. Grease on it's own will require taking apart and re-applying grease (as it washes out).
 

designerRob

CJ-8 Member
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Allen Park
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MI
As Glenn Haege always said, "water always wins". Water always seems to find a way into where you don't want it to be, no matter what you do.
I think a rubber gasket like material behind the light would be good. But still periodic removal of the light for cleaning and inspection would be good too. I wonder if a few coats of plastidip on the back of the lights would work well.
 

barrys

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East Norriton
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PA
How about using never seize. NO idea if it would work, just a thought as I was using some the other day.
 

Randyzzz

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You’ve got to find that happy medium between something that will conform to the surface, not absorb water, not wash out, and be compressible enough to not distort the sheet metal. That’s why I thought the EVA foam showed promise. It crushed flat as a sheet of paper, yet sealed out the Savvy twilights when they were on Copper. I’ll keep you updated on my findings.

Heres an explanation of it’s properties and uses-
 
Last edited:

MomoJeep

Basic User
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City
Seattle
State
WA
You’ve got to find that happy medium between something that will conform to the surface, not absorb water, not wash out, and be compressible enough to not distort the sheet metal. That’s why I thought the EVA foam showed promise. It crushed flat as a sheet of paper, yet sealed out the Savvy twilights when they were on Copper. I’ll keep you updated on my findings.

Heres an explanation of it’s properties and uses-
I wonder if that's the same as this... https://www.4wheelparts.com/p/tough-stuff-rocker-guard-gasket-184/_/R-TOUGH-000184
 
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