Expansion tank to thermostat housing to heater core Your cooling system is held together by an integral series of hoses and pipes that carry hot coolant between your engine and radiator. Designed to be both strong and resistant to chemicals, your engine’s coolant hoses should never be neglected. An easy way to gauge the condition of a coolant hose is just by squeezing it. A new hose will feel firm, with the fiber reinforced rubber adding strength. An aging hose in need of replacement will feel spongy as the interior disintegrates and the rubber succumbs to years of high heat and high chemical exposure. If you are planning on doing a coolant flush, thermostat, or work on any part of your cooling system that requires a partial or full drain, it’s a great time to go through and replace the coolant hoses that feel less than stellar, and hit the road with a nicely refreshed cooling system.