Heating & Air Conditioning
Work Example 8

WorkKey Level: 7
NATEF Automotive Tasks: VII.C.5, VII.C.6

The chart below shows the relationship between the boiling point of coolant and the percent antifreeze coolant content of the coolant.

Percent Antifreeze in Coolant	Boiling Point of Coolant (°F)
0	212
10	213
20	214
30	217
40	223
50	228
60	236
70	245
80	258
90	270
100	330

You have tested a car’s coolant system and found that the coolant is 20% antifreeze.  The car will hold 12 liters of antifreeze when full.

a.   What is the boiling point of the coolant in the car with coolant containing 20% antifreeze?

b.  If you want the boiling point to increase to 245°F, what percent antifreeze should the coolant be?

c.  How many liters of coolant should you remove from the system so that replacing by 100% antifreeze will raise the boiling point to 245°F?

Solution:

a.  Reading off of the chart, the boiling point is 214°F.

b.  Reading off of the chart, the percent of antifreeze is 70%.

c.  original amount = new amount
     0.20(12 – x) + x = (12)(0.70)
    2.4 – 0.20x + x = 8.4
    2.4 + 0.80x = 8.4
    0.80x = 6
    x = 6/0.80 = 7.5 liters