Our master bathroom has developed a leak at the vent fan which is installed in the ceiling and vents straight up through the roof. It's a vaulted ceiling with a *very* gentle pitch. Asphalt shingle roof with a pretty standard steel roof cap tied into the shingles and secured with two roofing nails in the holes at the bottom. I did it myself 10+ years ago and no issues until now.

Upon inspection I noticed one of the nails was lose and the bottom edge of the roof cap had warped up a bit. I pushed it back down and sealed the bottom edge with black sealant.

Still leaking.

Granted, the water could always be coming in from somewhere else. But would there be harm in screwing the bottom edge down (gently) with a good dose of sealant underneath, or should I think about reinstalling a new cap? Other ideas?

Does it happen during rain? Or just developed? I ask because if vent hose goes through unheated space, during the winter the moist warm air condenses when it hits the cold. The vent hose could be holding that water, until the hose springs a leak..... Consider pulling the fan down to gain access so you can see more.

No, definitely only happens when it rains and it's recent. It's a very short vent pipe as well, perhaps 12", just enough for the elbow and out the roof…

We have three sections of very shallow roof which constantly drive me nuts.

I would still pull the fan down. Good luck

I would still pull the fan down. Good luck
Agree, likely there's some staining that will indicate the source...

thanks

Make sure Dana is standing in the yard telling orders at you when you are on the roof.
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The leak could be located between the vent collar and outer diameter of the external vent pipe.
Also look for breaks in the sheet metal seams
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it's probably a leak somewhere above or higher than the vent and once it reaches that point it follows it. Either that or rain is driving up into the vent cap

go up with a hose and have someone inside

when peering into a dark attic space
with just a small flashlight during a rain storm

it's easier to SEE the golden "raindrips" catching the light
than having it totally illuminated...