In those instances i would also remove the roof vent itself and put fresh butyl tape under the flange and re secure it to the roof.
How to remove old sealant from rv roof.
If the sealant and the roof are clean you should be able to apply a new one easily.
This cleaner even if left to dry.
If its hard to remove leave it in place and seal over it.
On the other hand a caked and hard to remove old sealant means that you can just leave it be.
Not all new dicor lap sealant products work with every roof cleaner or sealant removal.
Although this project tested our patience and stamina we know t.
A couple of other points.
Remove old sealant from rv roof.
If however the old sealant has become brittle and is flaking or peeling off then it will be necessary to remove all of it and start over.
Then you should be able to seal right over the old one without any problem.
By oscillating back and forth the machine made gentle cutting strokes that loosened the caulk.
Clean the old sealant if need be.
Clean the area with an rv roof cleaner and follow up with a good rinse with a wet sponge then once dry clean the area with a rag soaked with denatured alcohol.
Cleaning the old sealant first is essential.
The roof and sealant are clean.
Working on an aluminium roof of my old lazy daze mh i found that the roof sealant was easy to cut away by using a harbor freight multi purpose tool that had a chisel shaped blade.
In this video we begin tackling the monumental project of resealing the exterior of the rv.