Scrape the old sealant away from the camper's skylight using a putty knife. Skylight sealants may look like putty, silicone or tape and they need to be completely removed. Applying all-purpose silicone over the existing sealant is not a proper fix and will only lead to more damage.
Unscrew the screws holding the skylight to the camper roof and put them in a safe place. Lift the skylight and set it to the side. Remove the butyl tape under the skylight by scraping it with the putty knife. This tape may come off in one piece or be so badly degraded that it breaks in several places.
Clean the roof of the camper with a degreasing cleanser such as trisodium sulfate and a scrub brush. Don't use a wire brush as it could inadvertently scratch a rubber roof and contribute to future leaks.
Apply new butyl tape to the area where the skylight will be installed. Peel the paper backing and apply the tape slowly to prevent it from sticking to itself and causing bubbles or folds. Apply pressure to the tape to activate it. Use a rubber roller to apply pressure along the length of the butyl tape.
Realign the skylight atop the butyl tape and press it into place. Position the drill bit over each hole in the skylight and drill through the butyl tape and the roofing substrate. Reinstall the skylight screws, making sure they are flush with the metal flashing.
Cut strips of sealing tape 4 inches longer than each side of the skylight. Peel the paper backing from the tape and apply it in the same fashion as the butyl tape. Push the rubber roller along the tape to create friction and speed the bonding process.
