Insta-hot sputters

[TrailCodger]

I have an ISE on my kitchen sink that sputters and spits during use. It's similar in action to entrained air in the water, however, that is not the case as it sputters continually. Also, it is not overheating, or steam related, as it sputters even with a fresh cold tank of water. Do you have any ideas?

 

[Jadnashua]

If it has a lot of mineral deposits inside of it, water will seep into small pockets closest to the heating elements, and, even if the main body of the thing is still cold, those little pockets of water could be boiling and spouting steam jets.