Page 168 - 05. Subyek Teknik Mesin - Automobile Mechanical and Electrical Systems Automotive Technology Vehicle Maintenance and Repair (Vehicle Maintenance Repr Nv2) by Tom Denton

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152 Automobile mechanical and electrical systems

Figure 2.137 Air-cooled system

Figure 2.138 Water-cooled system

coolant should be changed at these intervals. Selection of the correct coolant
mixture must be made to meet the manufacturer’s specifi cations. Aluminium-
alloy engines are more prone to corrosion than cast-iron engines.
Antifreeze is mixed to a specifi ed ratio with water. Many manufacturers specify a
50/50 mixture of water and antifreeze, which allows higher engine temperatures
before the coolant boils and prevents freezing. An ethylene glycol antifreeze
solution has an added advantage. It forms a semi-solid wax solution prior to
solidifi cation and this enables any expanding ice crystals to move within the
water passages.
A 50/50 coolant mixture will increase the boiling point to about 105°C (222°F)
and provide protection down to 34°C ( 30°F). For colder temperatures down
to 65°C ( 90°F), a maximum mixture of 65% ethylene glycol can be used.
Higher concentrations begin to freeze at higher temperatures and therefore no
more than 65% ethylene glycol should be used.
Many areas have ‘hard’ water that contains calcium or chalk. This separates from
the water when it is heated. Deposits can form inside the water jacket or radiator
where they can block small water passages. Frequent topping up with tap water
in hard-water areas should be avoided. In some areas, it may be recommended
to use distilled water, or water from outside the area.