Rumble's abilities have no cost related to them, so the use of his abilities is only limited by cooldowns. Instead, he uses Heat as his secondary bar. Rumble starts with 0 heat, and it caps at 100.
Rumble's basic abilities generate 20 heat when used. When Rumble reaches 50 heat, he is in the "Danger Zone", causing all his basic abilities to have enhanced effects. When Rumble reaches 100 heat he overheats, silencing himself for 6 seconds after which he will cooldown completely. While not overheated, after 4 seconds of not using his basic abilities he will start losing heat at a rate of 5 every half second, and 2.5 seconds later at a rate of 10 every half second.