WW, I posted about a similar Garrett's coil problem and called Garrett's customer service department Rep.
The young fellow assured me that the coils are covered inside with two or more coatings of epoxy sealer prior to the final plastic coating being installed.
A very close inspection of the "cracks" I found revealed to me that it was a less than perfect job of finishing off the edge where the bottom cover and the top came together. On my coil the "crack" doesn't penetrate into the coil and is only a cosmetic issue which doesn't cause any problems.
I was assured also that Garrett gets coils coated with all sorts of "protective"coatings and hasn't failed to honor a warranty yet because of these coatings.
The available coil cover that fits most of these coils are disks that hydroplane under water and are a pain to use, therefore most Hunters use a coating of one kind or another.
This is my second experience with coil damage. My Infinium 8" Mono wore through on the bottom surface a few years ago and it was right in the middle of prime hunting season, so I "fixed it" rather than send it to Garrett and be without it..
I rinsed it with clean water, then alcohol and then I carefully dried it out. Marine epoxy was then used to fill the voids and I coated the whole coil with tool handle coating in bright yellow.
It still is one of my favorite coils and works great!!
Good luck with your coil Friend and know that Garrett will take care of if you decide to send it in, but it also may not be necessary.
CJ
