I recently changed the valve cover gasket on my 2014 mainly because of oil around the #1 spark plug. There was backside seepage that created an oily smudge but was of no consequence (just wipe it off) and not a reason in and of itself to change the gasket.
I used a Mazda gasket and Mazda gray sealant and watched 2 youtube videos and viewed the diagram in the CX-5 shop manual regarding locations to place sealant. Also after removing the valve cover ,the factory sealant had to be scraped off so the locations were obvious anyway.
The wiring looms, especially the one at the front of the engine adjacent to the cam phasers make it a tricky, tight fit to maneuver the cover back in place without dislodging the new gasket on the timing chain.
After careful cleaning, sealant application at the indicated spots on the head and proper torqueing the bolts I started it to check for leaks.
Immediately got a small leak at the front cam phaser location about where sealant was applied on the inside. A small steady leak the was spitting oil and a few bubbles.
Possibilities ran through my mind.
1) I didn't apply enough sealant at that location
2) I started it too soon and didn't let the sealant cure long enough ( very real possibility)
3) I dislodged a section of the gasket out of it's groove in the valve cover when installing.
Choices at that point were to remove the valve cover, go through the cleaning and sealant application again and hope the gasket wasn't pinched permanently/damaged and wouldn't seal properly. Well, this wasn't going to happen and I didn't have another new gasket on hand. And this leak needs fixed one way or another.
Since the gasket fit tightly in the valve cover groove I ruled that out and figured it was sealant related. And if the sealant on the inside is insufficient then it's gonna get sealant on the outside.
Here's some pictures.
It isn't pretty and makes me feel like a hack artist but it's holding and nobody sees it under the engine cover anyway. The first gasket lasted ~ 10years and here's hoping this one does too. And it ain't a new car anymore.
Just relating my experience and good luck to anybody who is contemplating doing this job.
Being that leaks can be insidious and travel along seams, I applied sealant extending well beyond both sides of the leak area, so small leak and lotsa sealant.
P.S. I don't remember how it compares to Ultra Gray or other sealants but the Mazda sealant seems to be good stuff. It wasn't too expensive and wanted to use what is recommended considering the nature of the repair.
P.P.S --- This is IMPORTANT --- the first tube of Mazda sealant I purchased was online(this goes for all sealants IMO, so check it) and was already expired by 6 MONTHS !!!. The vendor refunded and I discarded the tube. The second tube I got from the local dealer (more expensive but should have went there first). Before driving there I asked the dealer parts person to check stock and the expiration date stamped on the crimp on the bottom of the tube. All good, had 7 months until expiration. The reason I bring this up is that it's not too desirable to get into the job and find the expired sealant already stiff and partially cured inside the sealed tube and doesn't spread out well and tends to ball up. The other possibility exists where the curing agent has expired and the sealant never cures fully and 2 days later it's still just wet or tacky. Soooo, check the expiration dates.