PRIN. OF INTERNAL COMBUSTION ENGINES - OD1619 LESSON 2/TASK 3
FIGURE 74. EXPANSION TANK.
j.
Closed Cooling System (figure 75 on the following page).
(1) Purpose. The purpose of a closed cooling system is twofold. First, the
system is designed to maintain a completely full radiator at all times. This will
increase the efficiency of the system by allowing a maximum amount of coolant in
the system during all operating conditions. Second, during an overheating
condition, the closed cooling system prevents coolant loss through the overflow
line by collecting it in the recovery tank.
(2) Operation. As the temperature of the cooling system rises, the pressure also
will rise. This will open the pressure valve in the pressure cap, causing coolant
to exit through the overflow tube, thus venting excess pressure. An opentype
cooling system will empty coolant onto the road, causing a low coolant level after
the temperature returns to normal. When a closed cooling system is used, the
overflow line is connected to the bottom of a coolant recovery tank to catch and
hold any expelled coolant. As the temperature of the coolant drops, the
corresponding drop in pressure causes atmospheric pressure to push the coolant in
the recovery tank back into the cooling system through the open vacuum valve in the
pressure cap.
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