0381026 JOHNSON DRIVESHAFT AND PIN ASSEMBLY

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 system to reduce the turbocharged air temperature before it enters the engine intake manifold.Lower intake air temperature allows more air to enter the cylinder, resulting in more complete fuel combustion and reduced exhaust emissions.Air-to-air aftercoolers can achieve charge air temperatures lower than water-to-air systems for additional efficiency.
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, GM-6038M or equivalent.Only use a greater concentration (above 30%) of antifreeze as needed for anticipated outside temperatures.Ethylene glycol raises the boiling point of water.Do not exceed a coolant mixture of 60% ethylene glycol to water since a concentration above 60% 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.
Air Intake System
Never run the engine without an air cleaner installed or with a damaged air cleaner. Dirt will enter the engine and cause premature wear and damage to engine components.Service the air cleaner at regular intervals as determined by the operating environmental dust conditions. Check the air cleaner service indicator (if equipped) daily.As the air cleaner element becomes plugged, the difference of air pressure between the inlet side (dirty side) and the engine side (clean side) will increase. Service the air cleaners regularly or when the air cleaner service indicator diaphragm enters the red zone or the red piston locks in the visible position.Inspect the air intake hoses, elbows and gaskets for cracks or damage, replace as needed. Check for loose clamps, tighten as needed.Check the precleaner (if equipped) daily for accumulation of dust and debris.The Caterpillar air cleaner element may be cleaned up to six times, but must be replaced annually. The element when cleaned, should be thoroughly checked for rips and tears in the filter material and for gasket damage.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, a reduction in fuel economy and possible engine damage.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 temperatures and high winds, insufficient coolant water heat may make the cab uncomfortable for overnight sleeping. Some trucks can be modified to use fully closed winter fronts for overnight sleeping.However, 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., set at 150°F (65°C). Temperatures exceeding150°F (65°C) can cause power loss and potential engine damage.Caterpillar recommends installation of an inlet air temperature gauge. For the ATAAC (Air-To-Air Aftercooled) engines, air temperature in the intake manifold should not exceed 150°F (65°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 150°F (65°C) willbe encountered under normal operating conditions.A hose failure or significant system leak will cause a large drop in boost pressure and power. The engine can be operated at this power level long enough to reach a safe stop or repair area. Sustained operation under this condition should be avoided.A slight reduction in power or response or a small increase in exhaust temperature may indicate a small air leak in the charge air cooler core or piping.Data to evaluate the Air-To-Air Aftercooling system can be obtained from the April, 1988 "Truck Engine Application and Installation Guide," Form LEBT8121.