12567 1 Mercury OIL SEAL, CRANKSHAFT-UPPER

Operation of ATAAC
Heated compressed air from the engine turbocharger is conveyed to an air-to-air aftercooler that is positioned in front of the engine radiator. The combined effect of the engine fan and ram air moves cooled air through the aftercooler system to reduce the turbocharged air temperature before it enters the engine intake manifold.Air-to-air aftercoolers can achieve charge air temperatures lower than water-to-air systems for additional efficiency.Lower intake air temperature allows more air to enter the cylinder, resulting in more complete fuel combustion and reduced exhaust emissions.Refer to the "Truck Engine Application and Installation Guide," Form LEBT8121 April, 1988 for more information.
To maintain an adequate water pump cavitation temperature for efficient water pump performance in an Air-to Air Aftercooled engine, Caterpillar recommends that the coolant mix contain a minimum of 30% Caterpillar Antifreeze or equivalent. Only use a greater concentration (above 30%) of ethylene glycol as needed for anticipated ambient temperatures.Ethylene glycol raises the boiling point of water.Do not exceed a coolant mixture of 65% ethylene glycol to water since a concentration above 65% ethylene glycol will reduce the engine's freeze protection and increase the possibility of deposit formation in the cooling system.Dowtherm 209 Full-Fill coolant cannot be substituted for ethylene glycol, due to its inability to raise the water pump cavitation temperature. Dowtherm 209 Full-Fill coolant lowers the boiling point of water.
Winter Fronts
Caterpillar discourages the use of winter fronts or other air flow restriction devices mounted in front of radiators with air-to-air aftercooled engines. Air flow restriction can cause higher exhaust temperatures, power loss, excessive fan usage and a reduction in fuel economy.However, if a winter front must be used, then it should have a permanent circular or diamond-shaped opening directly in line with the fan hub and must have a minimum opening dimension of at least 120 sq. in. (770 sq. cm).A centered opening, versus a side or edge winter front opening is specified to provide sensing when viscous fan drives are used and/or to prevent an interrupted air flow on the fan blades that could cause a fan failure.The greatest need for winter fronts appears to be for trucks parked overnight. At very cold ambient and high winds, insufficient jacket water heat may make the cab uncomfortable for overnight sleeping. Some trucks can be modified to use fully closed winter fronts for overnight sleeping.
Failure to open the winter fronts in the morning could cause engine damage and/or loss of fuel economy.
Caterpillar recommends that a winter front package include an intake manifold temperature warning device such as a temperature light indicator, warning buzzer, etc. to monitor the intake manifold air temperature. The air temperature should not exceed 160°F (70°C) with the winter front installed because of power loss and potential engine damage.Caterpillar also recommends installation of a 4W2682 Indicator (inlet air temperature gauge) to allow the operator to monitor the intake manifold air temperature. For the ATAAC (Air-To-Air Aftercooled) engines, air temperature in the intake manifold should not exceed 160°F (70°C).This temperature provides engine protection for full winter front closure and can serve as a diagnostic tool for a malfunction of the charge air cooling system. It is not anticipated that a temperature of 160°F (70°C) will be encountered under normal operating conditions.Data to evaluate the Air-To-Air Aftercooling system can be obtained from the April, 1988 "Truck Engine Application and Installation Guide," Form LEBT8121.