Heater Core Bypass Hose Coolant Crossover For 98-up GM Chevy Pontiac 551699 LSX LS1 LS2 LS3 LS6 LS7 LM7 LT1 LT4 LQ4 LQ9. Reduce curb weight by allowing safe removal of the heater core. Prevent and fix the coolant leaking and engine overheating problem.