Don't worry about the jar, we haven’t seen any jar cracking or warping due to heat. But the plastics and glues may be damaged, so you don't want overheating for long periods of time.

Lower the concentration of Electrolyte. At ¼ teaspoon baking soda, the unit will normally stay cold or lukewarm, and moderate amount of HHO will be produced. A flat teaspoon may heat up the jar moderately, while producing a fair amount of HHO. Two teaspoons may be ok for cold environments, but may cause overheating and meltdown in other areas. For me 1 and a half teaspoons is the optimal balance: maximal HHO with no overheat problems.

In H2O mode (no 12 Volts) the unit does not heat up unless mounted next to a very hot part of the engine. Which brings us back to HHO units overheating even with moderate levels of Baking Soda – find a cooler place in the engine compartment. If you have the choice, select a position in front of the engine or even in front of the radiator, rather than behind it, because that's where much cooler air flows in.