Radiator Hose
A heavy-duty reinforced rubber hose that transports hot coolant from the engine to the radiator, and cooled coolant back.
Radiator hoses are flexible, heavy-duty rubber conduits that connect the stationary radiator at the front of the vehicle to the vibrating engine block. There are two primary radiator hoses: the upper radiator hose, which carries hot coolant from the engine thermostat housing into the radiator, and the lower radiator hose, which carries the cooled fluid from the bottom of the radiator back to the water pump inlet.
Because they must withstand high temperatures, cooling system pressures (typically 12 to 16 PSI), and constant engine vibration, radiator hoses are constructed from synthetic rubber reinforced with internal fabric or cord layers. The lower hose often contains an internal metal spring to prevent it from collapsing under the suction created by the water pump at high engine speeds.
Over time, the rubber degrades due to heat cycles, oil contamination, and electrochemical degradation from the inside. Symptoms of a failing radiator hose include visible cracks, bulging, soft or spongy spots when squeezed, or coolant leaks around the hose clamps. If a hose splits or bursts while driving, it can lead to a sudden loss of coolant and severe engine overheating. Hoses should be inspected regularly and replaced as preventative maintenance.