A heat sink is used to absorb heat produced by a vehicle. The heat sink uses a steam reformer to create an endothermic reaction between two fluids. Excess heat from the vehicle's engine is used to heat the reactor to facilitate the endothermic reaction. In some embodiments, the reactant fluids are pre-heated by absorbing heat from various components of the vehicle. Excess heat from the various components or from the vehicle engine is used to vaporize the fluids before the fluids enter the reactor.