Why is there coolant on sparkplugs?

[jimstaz]

why do o have coolant on my spark plugs.. the car idles fine... is somehting going wrong with the engine is is the coolant normal? just doing a tune up... and recently did replace the radiator about a month ago.
:001_07:

[mazpower]

Coolant on spark plugs means the seals have failed and it's time for a rebuild.

[t_g_farrell]

You have an internal coolant leak for sure. You can try the AlumaSeal in the coolant. I've had
success with it on a leak between the front plate and the front housing at the top. It took
a few days but now the leaks is pretty much gone. Some folks have done this and kept a
motor running for over 50K longer.

Of course this was on an old 12A and not an rx8. YMMV.