Third brake light leak prevention ? (1 Viewer)

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Hi,

Been trying searching but couldn’t find an answer.
I had rust in the rear hatch. Got that repaired and now keen to ensure it doesn’t happen again. Dealer said it was coming from the rear glass seal but reading the forum it seems the culprit is the third brake light.
Is there a guide on how to ensure it is watertight ? Some seal to change ? Any part reference for such seal ?

Thanks for help

T
 
Recent thread on this and several others on the forum. Basically you remove the 3rd light, inspect it for cracks since water can leak through them, if ok continue. Remove the old foam from the bottom of the light, clean all surfaces, add new bead of silicone where old seal was, reattach light and tighten, then run a bead of silicone around the entire outside edge of the light. Let dry for 24hrs.

 
that seal, same as the seal on the tail light is just a crappy design, I mean cushion, it doesn't seal much. The light itself also. I'd bet it curves tighter in the heat to. idk.
There's an engineer out there that thought, ehh, two screws is fine, we don't need four. idiot


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I had the 3rd brake light leak a few months ago and attempted to fix with RTV. Looked like a good seal, but found a leak a few weeks later.

Decided to go the butyl rope route the second time. The RTV was a bear to clean off, but I am more confident in the seal, and it has not leaked since.

3M Butyl Rope
 
Butyl rope is a proven solution. Here’s a thread with tips & pics: new third upper brake light, would you add a strip of silicone?

1. Remove brake light, clean off old seal
2. Apply butyl rope to body sheetmetal
3. Roll it a little flat with a wax paper barrier
4. Warm up butyl with heat gun
5. Install brake light, tighten screws slowly to prevent cracking while butyl gets squished
 
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FWIW there was butyl rope on mine and it was leaking. Maybe the paint shop that sprayed my upper hatch installed that butyl rope and probably didn't pay close attention to making a good seal.

There is a gap between the fixture and the hatch when the lamp is tightened down, so the problem with not putting a bead of silicone around the outside edge of the lamp is water and crud will get under it and migrate, or build up. If you're good with laying a bead of silicone, I think this is an acceptable method. The only downside I can see is it will take a little more effort to remove the lamp should it ever need replacing.

We'll see if the GE 10yr window silicone I used stands the test of time.
 
Butyl rope is a proven solution. Here’s a thread with tips & pics: new third upper brake light, would you add a strip of silicone?

1. Remove brake light, clean off old seal
2. Apply butyl rope to body sheetmetal
3. Roll it a little flat with a wax paper barrier
4. Warm up butyl with heat gun
5. Install brake light, tighten screws slowly to prevent cracking while butyl gets squished

I used butyl tape with good results. And it's easy to remove if I ever have to do it again.
 
idk, I've removed a ton off headlight plastic and glass, and it ain't easy unless the temp is perfect.
you got a drive in oven?
 
Thanks a lot for the replies. That’s clear, will get it done next weekend
 
To echo what others have said, the extra measure of clear silicone around the outside is the real key. It solves the bad design. While it’s worth removing the light, cleaning and using butyl rope, I’ll bet just applying silicone would solve the issue. I did both, by the way.
 
To echo what others have said, the extra measure of clear silicone around the outside is the real key. It solves the bad design. While it’s worth removing the light, cleaning and using butyl rope, I’ll bet just applying silicone would solve the issue. I did both, by the way.

As long as the brake light isn't cracked, you are correct that it should work. Mine was split, 1/3 of the way down, on the left. So I took the added measure of removing it. As it warped over time it cracked into two distinct pieces. I expect the other side will probably crack at some point in the same place due to stress.
 
I had new brake light leak on a newly installed lens by Lexus.. I pulled and seal to body/rear hatch appeared just fine. Although no good after pulling, as it's a double sided tape. So I was not convinced it was seal between body and lens. It may actually have been between front and back of lens assembly, where they are glued/sealed together.

I used butyl new third upper brake light, would you add a strip of silicone?
 
As long as the brake light isn't cracked, you are correct that it should work. Mine was split, 1/3 of the way down, on the left. So I took the added measure of removing it. As it warped over time it cracked into two distinct pieces. I expect the other side will probably crack at some point in the same place due to stress.
I ended up buying a hatch from a junkyard because of the rust issues from years of leaking. I'm saving the extra brake light as I'm sure mine will crack at some point as well!
 
Who ever designed the third brake light and it's placement on the 100 series should commit harakiri. Okay it looks good being flush with the lines of the body, but, the problems it has caused are far worse than it's esthetics.
 
To echo what others have said, the extra measure of clear silicone around the outside is the real key. It solves the bad design. While it’s worth removing the light, cleaning and using butyl rope, I’ll bet just applying silicone would solve the issue. I did both, by the way.
Thanks, really enjoy the insight all contributors put out there for people like me can benefit from.
 

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