Not a small core
Hi REB
Enceladus' density is about 1.7 - a lot higher than its siblings. That means the rocky core is about 35%, by volume, of the moon. It extends to about 71% of the radius of Enceladus - and could be even closer to the surface under the south pole if asymmetric.
What's "hot" is that the core is probably still molten, kept fluid by the unique set of tidal forces acting on it, but initially melted by Al26 in the planetesimals that formed Enceladus aeons ago. If Al26 is the main heat source in all the Saturnian moons then they formed within the first two million years of the appearance of Al26 in the solar system.
Adam