The engine cooling system is similar to that used in a gasoline engine, except that it is larger capacity. (See Figure 2-43).
The purpose of the cooling system is to dissipate heat arising from combustion and to keep the engine at its most efficient operating temperature at all engine speeds and all driving conditions. During combustion of the air fuel mixture in engine cylinder, the burning gases may reach temperature as high as 4,000 °F. Some of this heat is absorbed by the wall of the cylinder, the heads and the pistons. These parts must be cooled so that they are not damaged from excessive temperature.
While it is critical that the engine not overheat, it is desirable that the engine operate as close as possible to the limits. This is because the engine is less efficient when it is cold. Therefore, the cooling system includes devices that prevent normal cooling action during warm-up of the engine. These devices are called thermostats and only allow flow of the coolant after the engine reaches normal operating temperature.
The cooling system in most all automobile and truck applications is a liquid coolant system. The liquid coolant
system is made up of water jackets in both the cylinder head and in the cylinder case, a pump, an engine fan
and a radiator.
GM 1825 M Spec. Coolant is used in the 6.2L Diesel. It is a new specification with modified formulations to lessen aluminum transport deposition (cavitation erosion). When engines with aluminum components are used with coolants not formulated for aluminum, plugging of radiators and engine overheating has been observed. Aluminum compounds in the radiator tubes caused the plugging.
Both service and owners manuals call for GM 1825 M Spec. Coolant. The new coolant (1052753) conforms to GM 1825 M.
