[BrianG]

Welcome to the forums!

That's fairly common on the Quarks - they tend to overheat because of the way they are put together. The ESC guts are held on to the case by a sticky thermal pad. Over time (sometimes very short), the sticky part lets go, so there is no longer any cooling from the ESC to the case. If this is the case, you have two options: 1) send it back to Sky&Technology for repair, or 2) perform the "internal mod".

The internal mod involves taking the ESC apart, removing the crappy thermal pad, and using thermal epoxy in place. You also have to make a new heatspreader slab as the existing one is too thin once you remove the pad. This voids the warranty though, but does wonders.

No matter what you do, it's best to add some sort of heatsink to the case to help shed the heat. The case is rather thin and doesn't function well as a heatsink unaided. Mike has a heatsink in his store, or you can come up with your own method.