Clean the area surrounding the vent with degreaser. Allow the area to dry completely.
Roll out the self-adhesive roof repair tape along one side of the vent. Use scissors to cut the tape off at the appropriate length. Repeat on the remaining three sides of the vent.
Lay the repair tape down along the seam on one side of the vent. Remove the backing from the starter edge. Press the starter edge of the tape down onto the surface of the roof. Remove the remainder of the backing slowly, pressing the tape down as you go. Rub the tape firmly into place to activate the bonding material.
Repeat steps 2 and 3 on the remaining three sides of the vent.
Apply a bead of self-leveling roof sealant around the vent with the caulking gun. Fill the seams completely with sealant.