also check where the screws are on the outside of the brake light sometimes they crack around there or they dont have a good seal around the screws

 

A pretty good little trick I found for diagnosing leaky windows I learned when I worked installing auto glass. A can of foaming glass cleaner (or any foaming liquid that wont damage paint or break down the integrity of the rubber molding or urethane) and an air source can tell you exactly where its leaking. Just spray the foam over the outside molding in the questionable area, and reach inside the truck up under the headliner and spray air around the inside perimeter where the glass is glued in. It'll bubble and you can run a fresh bead under the outside molding. Works like a charm.

 

OOooooo, neat trick. Yep, I am definitely making note of that one.

Thank You.

 

Wow thanks for all the tips. I did seal around the roof gaskets and around the back window with silicone on the outside and it hasn't rained since I did it.If it leaks again ill try ill the tips I got. I don't have a compressor so what do you think I should use for air? would a can of compressed air work? And where do I get the foaming glass cleaner would Walmart or an auto parts store like advanced have it? thanks great tip!

 

Wally World will have the cleaner. A can of compressed air (such as used for blowing out electronics and such) doesn't have the pressure required. You need something a bit more serious than that.

 

You have some great tips on how to find the leak, I'll pass a tip on don't use silicone to seal the leak the are much better products out there. Being a retired marine tech I see peolpe use silicone all the time to seal stuff and it just does not hold up well to the elements. have a look at this product one of many but I used this one all the time. Come's in diff color's, just make sure you use the prep cleaners with it.

http://boatlife.com/life-calk-sealan...7e8c40cab8e7e8

 

Use a garden hose and spray water all around 3rd brake light,guaranteed to leak.Dont forget to to pull down the headliner in the corners,you will see leak once you drench the brake light.Good luck!

 

I found my 3rd brake light leaking so I pulled it out and made a gasket out of gasket sheet, rubber/fiber cross medium thickness, added a little clear silicone and walla!

Here is what I use because nobody ever has my gaskets so I always make my own:
https://www.napaonline.com/Catalog/C...493_0334851034