Due to environmental and safety concerns, the towing winch drive diesel engine cooling water system is treated with propylene glycol for protection against freezing. According to the illustration, what would be the limit of protection if 40 pints of propylene glycol are used in treating a cooling water system with a volumetric capacity of 10 gallons? Illustration MO-0209
• Convert the amount of propylene glycol to a percentage by volume of the total cooling system capacity • Use the propylene glycol (PG) curve on the illustration, not the ethylene glycol (EG) curve • Match the % glycol by volume to the corresponding freeze protection temperature (°F) on the vertical axis
• How many pints of total coolant does the 10-gallon system hold, and what fraction of that is the 40 pints of glycol? • Once you know the % glycol by volume, where does that point fall on the PG line of the graph, and what temperature does it line up with on the left-hand (°F) scale? • Which of the answer choices is closest to the temperature that corresponds to that percentage of PG on the chart?
• Be sure you convert gallons to pints correctly before finding the percentage • Verify you are reading only from the PG (propylene glycol) line, not the EG line • Double-check you are reading the temperature from the °F side of the scale when comparing to the multiple-choice answers
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