OPERATOR AR 4612972 - Caterpillar

Valve System Components
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(24) Rocker arm (25) Pushrod (26) Valve bridge (27) Valve spring (28) Valve (29) LifterThe valve system components control the flow of inlet air into the cylinders during engine operation. The valve system components also control the flow of exhaust gases out of the cylinders during engine operation.The crankshaft gear drives the camshaft gear through an idler gear. The camshaft must be timed to the crankshaft in order to get the correct relation between the piston movement and the valve movement.The camshaft has two camshaft lobes for each cylinder. The lobes operate the inlet and exhaust valves. As the camshaft turns, lobes on the camshaft cause lifters (29) to move pushrods (25) up and down. Upward movement of the pushrods against rocker arms (24) results in downward movement (opening) of valves (28) .Each cylinder has two inlet valves and two exhaust valves. The valve bridge (26) actuates the valves at the same time by movement of the pushrod and rocker arm. Valve springs (27) close the valves when the lifters move down.Air Inlet Heater (If Equipped)
The engines are equipped with an electric heater that is located behind the air inlet elbow. The electric heater has two functions:
Aid in starting
Aid in white smoke cleanup during start-upUnder the proper conditions, the ECM turns on the electric heater.The system can deliver heat for 30 seconds prior to start-up and during cranking of the engine. After the engine has started, the system can deliver heat constantly for seven minutes, or the system can cycle the heat for 13 minutes. During the heating cycle, the heat is on for ten seconds and the heat is off for ten seconds.If the air inlet heater malfunctions, the engine will still start and the engine will still run. There may be a concern regarding the amount of white smoke that is present. Also, there may be a concern regarding the need for an alternative starting aid.System Components
The system of the air inlet heater consists of the following basic components:
Relay of the air inlet heater
Heater element
Coolant temperature sensor
Inlet manifold temperature sensor
ECM
Indicator lamp
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(30) Relay for air inlet heater
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Location of components (31) Air inlet heater (32) Stud for the ground strapThe relay of the air inlet heater (31) turns the heater ON and OFF in response to signals from the ECM.The air inlet heater (31) is located between the cover of the air inlet and the air inlet elbow. The heater element has a stud (32) for the ground strap that must be connected to the engine.The operation of the air inlet heater is determined by five different conditions:
Power up cycleThe air inlet heater and the lamp are turned ON for 2 seconds after the ECM is first powered up. This will happen regardless of temperatures and engine speed.
Mode of preheatThis check is for low altitude conditions. When the sum of the coolant temperature plus the inlet air temperature is less than 25° C (77° F), the ECM will turn on the heater and