21. Cooling, Coolants, and Water Pump and Oil Pump

In a diesel engine the parts in contact with the high temperature gases like piston, liner and cylinder head are kept within safe temperature limits by a coolant constantly circulated over the surfaces. The heat to be transferred to the coolant is estimated for EGR, non EGR and CNG engines. When the heat transfer fails, the oil becomes too thin to support the piston rings, valve seats and the valve stems and seizure takes place. Chemicals are added to demineralised water maintain the surfaces corrosion free and help in hardness salts remain suspended without forming solids to block the intricate passages. The coolant is maintained at a higher pressure by a cap on the radiator to enable higher boiling point; the freezing point can be lowered by adding ethylene glycol in eutectic proportions which also increases the boiling point. Addition of highly corrosive alcohol brings in additional responsibilities to the additive package, especially to protect the radiators and engine parts made of aluminium.