Glossary “coolant thermostat” Definition:
Component found in the coolant outlet of the engine to help prevent over-cooling conditions, and help to maintain proper engine operating temperature.

Glossary “coolant temperature override switch” Definition:
Temperature-controlled vacuum device that prevents overheating during idle speed, associated with late ignition, by advancing the timing to increase engine-idle speed.

Glossary “coolant temperature sensor” Definition:
Thermistor that sends a signal to the electronic control unit relative to the coolant temperature in a computerized engine-control system.

Glossary “coolant recovery system” Definition:
Cooling system having a vacuum/pressure cap, with a radiator-overflow hose leading into a separate reservoir. This saves coolant during hot operation as the heated coolant expands, and then returns it to the radiator when the system cools. This action maintains the proper coolant level in the radiator.

Glossary “coolant recovery tank” Definition:
Storage container that is used in a coolant-recovery system.

Glossary “coolant reservoir” Definition:
Tank or reservoir used for storing excess coolant; connected to the cooling system with a small-diameter overflow hose.

Glossary “coolant hydrometer” Definition:
Tool that compares the weight of pure coolant to water to give an indication of coolant strength.

Glossary “coolant jacket” Definition:
Hollow passages surrounding the cylinders in the block and the combustion chambers in the cylinder head.

Glossary “coolant passages” Definition:
Coolant passages, called coolant jackets or water jackets, surround each cylinder in the block, and through out the cylinder head(s) to provide a means to carry away unwanted engine heat. Coolant passages may also be found in intake manifolds and even in some throttle body assemblies.

Glossary “coolant pump” Definition:
Term often used for water pump. A centrifugal-type pump used to circulate coolant through the cooling system. May be ellectrically or mechanically driven.

Glossary “coolant circulation” Definition:
Movement of liquid throughout the cooling system by water pump action to move heat, generated by engine combustion, and routed to the radiator.

Glossary “coolant fan” Definition:
Electrically or mechanically driven fan to increase air flow across the radiator to facilitate heat removal.

Glossary “coolant fan relay” Definition:
Control device that is used to activate the electric-coolant fan at a pre-determined, high-coolant temperature.