EPDM Maintenance and Repair

The bubbling up may be due to using Dicor. If you read the tube you will see it has some petroleum distillates in it which will cause a bubble in the rubber. Give it couple to a few weeks and the bubble will go away.

I am not going to redo what I have done unless there is a new problem. I was looking to doing a better repair when I get to the other vents, as they are showing the same age related problems in the lap sealant that this one did, which ultimately revealed itself to be rusted flanges under the sealant from water intrusion.

Just curious why you feel the need to mess with it now? The trailer is almost 7 years old and it doesn't appear as though its been a problem thus far. I imagine the roof vent itself is keeping your rubber roofing from flying away.

I tend to fall in the camp of not fixing something that isn't broken...

google epdm cement. It's mostly a variety of contact cement. Every contact cement that I've used requires coating both sides and letting it tack up, and only then putting them together. With your situation it would be hard to keep both parts from touching long enough for them to set up. Worse, you're actually gluing cement to cement since this is a repair. That's hard to do usually.

Hopefully someone with experience sees your question. I would most likely use lap sealant squirted as deep as I could get it and then roll it to get the bubbles and weight it until it cured. Then install the vents once it was all cured up.