Timing chains and Water Pumps are changed at the same time to prevent wear in one part causing problems in the other. Worn belts, pulleys, and tensioners are some of the main reasons behind coolant leaks, damage to Thermostat Housings, and faulty pump seals, further leading to corrosion and engine overheating. To save on labor costs and another visit to your mechanic, inspect for wear in parts operated by the drive belt and have a Serpentine Belt Drive Component Kit handy if any surprises do show up.