If the seal around your tail light is not working properly, you can get dirt, rain, little critters and various other debris inside your boot. By learning how to remove the old broken seal and apply a new seal, you should be able to rectify this problem. There are several sealer options that you can choose from, such as butyl tape, liquid adhesive or sealant gel. You can purchase all of these sealants at an auto parts store.
Loosen your tail lights by opening the boot or tailgate. Then use a Phillips screwdriver or socket wrench to remove the screws or bolts that hold your tail light into place. You can leave the wiring connected during the cleaning process or you can grab the wiring connector at the back of the tail light and pull it directly away from the tail light assembly.
Remove as much of the old tail light seal with your hands. Scrape the rest off with a hard edge plastic scraper and a plastic scouring pad. Finish cleaning the area with a cleaner such as Goo Gone and a shop rag. Allow the area to dry thoroughly.
Apply the butyl tape, weatherstrip adhesive such as 3M, or liquid seal such as Permatex according to the product instructions. Immediately after applying the product to the surface around the tail light, put the tail light assembly back into place and secure it there with a clamp for at least 10 minutes or time specified on the product. This will help ensure it gets a good bond between the two surfaces.
Replace the screws or bolts that you removed in step 1 while you are waiting for the sealant to adhere. Reconnect the wiring as well (if you disconnected it) but make sure you do not disturb the adhering process when you do so.
Remove the clamp after 10 minutes or longer if the product specified a certain amount of time.