Lesson 5/Learning Event 2
FIGURE 67. CYLINDER HEAD COOLANT JACKET.
The pistons, valves, and walls of the combustion chambers and cylinders absorb the heat of the burning fuel.
Heat in the combustion chamber and cylinder walls is then passed into the jacket of coolant. The hot pistons
are cooled by passing heat into the coolant-filled cylinder walls. Heat from the valves is passed into the valve
guides and valve seats and then into the coolant jacket.
If the jacket of coolant remains still, it will absorb just so much heat and then begin to boil away. Therefore,
the heated coolant must be moved away and replaced.
A pump is used to move the coolant in the engine. The pump, generally known as a water pump, is usually
located on the front of the engine block. The system is designed so the pump forces coolant into the coolant
jacket in through the block and out through the head. The output of the coolant pump and coolant jacket
passages must be designed so that all of the heated coolant is moved. If coolant is allowed to stand still in
some places, uneven cooling or hot spots will develop.