Coil gasket
 

My nephew was changing plugs on my 03 trailblazer and we noticed the rubber gaskets are cracked on some of the coils. Is this a sign they need replaced?

Plus us there is some gunk on some of them. I assume I can clean them with qtips?

Thank you..

Cracked gaskets are always a good idea to replace, prevents moisture from seeping in and corroding the contacts, and just as a rule of standard if its dryrotted and not sealing, its not good.

I think you are talking about plug boots, you may not be able to buy just the boot and have to buy new coils, so it actually depends how deep the cracks are and what you want to spend. the gunk your talking about is prob dialetic gel and should be there - it stops corrosion

AC Delco PN 88958974 is the coil base gasket that seals the underside of each coil to the top of the valve cover. It can also be found individually under WVE/Airtex/Wells PN 4C3009 and Standard Motor Products sells a 6pc kit under PN F10001, both of which are much cheaper than the AC Delco part.

Here's a picture of the gasket I am talking about:
https://cimg2.ibsrv.net/gimg/blazerf...fccc199154.jpg
WVE/Airtex/Wells 4C3009 - RockAuto.com