How the coolant circulates- Top radiator hose Expansion tank and cap Top tank Coolant fillter plug The thermostat valve isopened by the waxinside melting. Water channels inblock and head Heater blower fan Heater Hose from heater Hose to heater from block Bottom radiator hose Water pump Engine driven fan Drain tap Bottom tank Radiator core

A typical water-cooling system with an engine-driven fan: note the bypass hose taking off hot coolant for the heater. The pressure cap on the expansion tank has a spring-loaded valve which opens above a certain pressure.

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How an engine cooling system works

A car engine produces a lot of heat when it is running, and must be cooled continuously to avoid ...