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Questions and Answers
What is the purpose of having a two-speed cooling fan system?
What is the purpose of having a two-speed cooling fan system?
At what temperature will the engine speed increase to TH-2?
At what temperature will the engine speed increase to TH-2?
What occurs when the engine coolant temperature exceeds 97 degrees Celsius?
What occurs when the engine coolant temperature exceeds 97 degrees Celsius?
What color indicates a hot condition on the temperature gauge?
What color indicates a hot condition on the temperature gauge?
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What is the primary benefit of pressurizing the cooling system?
What is the primary benefit of pressurizing the cooling system?
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When will the coolant fans operate at full speed?
When will the coolant fans operate at full speed?
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What temperature must the isolation switch be in RUN position for the engine speed to increase?
What temperature must the isolation switch be in RUN position for the engine speed to increase?
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What is one effect of engine loading limitation when the engine temperature reaches a critical level?
What is one effect of engine loading limitation when the engine temperature reaches a critical level?
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What happens to the cooling fans as the coolant temperature drops?
What happens to the cooling fans as the coolant temperature drops?
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How can water pump cavitation during high temperatures be minimized?
How can water pump cavitation during high temperatures be minimized?
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What is the primary purpose of the pressure cap in the cooling system?
What is the primary purpose of the pressure cap in the cooling system?
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What happens when the low water level switch opens while the engine is running?
What happens when the low water level switch opens while the engine is running?
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Which of the following is NOT a basic requirement for coolant suitable for EMD engines?
Which of the following is NOT a basic requirement for coolant suitable for EMD engines?
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What role do the engine mounted water pumps play in the cooling system?
What role do the engine mounted water pumps play in the cooling system?
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At what concentration must the borate-nitrate corrosion inhibitor be maintained?
At what concentration must the borate-nitrate corrosion inhibitor be maintained?
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What role does the vacuum breaker play in the cooling system?
What role does the vacuum breaker play in the cooling system?
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What happens if both electronic temperature probes fail simultaneously?
What happens if both electronic temperature probes fail simultaneously?
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What should happen if the low water level condition is detected while the engine is shut down?
What should happen if the low water level condition is detected while the engine is shut down?
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What is the function of the bypass line in the radiator system?
What is the function of the bypass line in the radiator system?
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What components does engine coolant primarily consist of?
What components does engine coolant primarily consist of?
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Where are the radiator banks located in the locomotive?
Where are the radiator banks located in the locomotive?
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What is the consequence of allowing the water level to fall below the LOW water mark?
What is the consequence of allowing the water level to fall below the LOW water mark?
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What triggers the display message 'ENGINE TEMPERATURE FEEDBACK FAILURE'?
What triggers the display message 'ENGINE TEMPERATURE FEEDBACK FAILURE'?
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How should powder and pellet form inhibitors be prepared before adding to the cooling system?
How should powder and pellet form inhibitors be prepared before adding to the cooling system?
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What component receives the coolant after it leaves the radiator?
What component receives the coolant after it leaves the radiator?
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What will occur if the engine's coolant fails to meet the requirement of not forming scale or sludge deposits?
What will occur if the engine's coolant fails to meet the requirement of not forming scale or sludge deposits?
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What is the purpose of the radiators in the cooling system?
What is the purpose of the radiators in the cooling system?
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How is the operation of the radiator fans controlled?
How is the operation of the radiator fans controlled?
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What can be inferred about the design of the water cooling system in the GM locomotive?
What can be inferred about the design of the water cooling system in the GM locomotive?
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What is the purpose of the electronic temperature sensing probes?
What is the purpose of the electronic temperature sensing probes?
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Study Notes
Water Cooling System of GM Locomotive
- The engine-mounted water pumps draw coolant from the expansion tank and lube oil cooler assembly, and pump it into the engine.
- Heated water leaves the engine and flows through two radiator assemblies for cooling.
- Cooled water returns through the oil cooler, completing the closed-loop cycle.
- A portion of the water is piped to the air compressor.
- No valves are in the air compressor cooling line; cooling is continuous when the engine is running.
Flow Diagram of Water Cooling System
- Components such as radiators, expansion tank, lube oil cooler, water pumps, and compressor are interconnected.
- Water flows from the expansion tank to the engine block through the water pumps.
- The heated water flows through the radiator assemblies.
- Cooled water then flows to the oil cooler and back to the expansion tank, completing the loop.
Electronic Temperature Sensing Probes
- Two electronic temperature sensing probes (ETP-1 & ETP-2) are located in the water line from the oil cooler to the water pump on the engine's left side, near the water temperature gauge.
- If either probe fails, the EM2000 computer sends a message to the display screen and archives the message.
- If both probes fail, the computer ignores the signal, sets engine speed to idle, and records a "NOT LOADING ENGINE TEMPERATURE FEEDBACK FAILURE" message.
Radiators and Cooling Fans
- Coolant picks up heat from the diesel engine, air compressor, and oil cooler, necessitating dissipation.
- Water temperature is regulated by radiator banks and AC motor-driven cooling fans.
- Radiators are located in a hatch at the top of the locomotive's hood.
- Each radiator bank has two quad-length radiator core assemblies bolted together.
- Headers are mounted on the radiator core to form inlet and outlet ends of each radiator assembly.
- A bypass line between inlet and outlet lines reduces velocity within the radiator tubes.
- Cooling water from the engine is piped to radiators, then to the oil cooler. Water returns to the pumps for recirculation.
Radiator Fans
- Eight-blade 52" cooling fans are controlled by the computer, which operates contractors.
- The computer manages fan sequencing, duty cycle, and speed (low/high), ensuring even fan and contractor wear.
- The two-speed cooling fan system includes two full-speed contractors (FCFA & FCFB) and one slow-speed contractor (FCS) per cooling fan motor.
- The system maintains coolant temperature within a predetermined range of 79°C to 85°C.
Coolant
- Coolant circulates through the engine to transfer heat to radiators.
- Engine coolant consists of water, corrosion inhibitor, and antifreeze (as needed).
- Coolant samples are analyzed periodically to maintain appropriate corrosion inhibitor levels.
- To be suitable for use in EMD engines, coolant must efficiently transfer heat, resist scale and sludge formation, prevent corrosion, and not deteriorate seals or gaskets.
Corrosion Inhibitor
- The primary corrosion inhibitor for EMD engines is borate-nitrate, available in powder and liquid form.
- Powder/pellet inhibitors are dissolved in a separate container before being added to the cooling system.
- Borate-nitrate concentration must remain above 5625 parts per million.
Water Pump
- Water pumps are impeller pumps.
- As the impeller rotates, coolant is drawn from the bottom of the radiator and forced through the pump outlet to the water jacket.
- Engine cooling water pumps (one per 8-cylinder engine) are self-draining centrifugal pumps.
- Pump drive shafts are supported by two permanently sealed grease-lubricated ball bearings requiring no maintenance.
Hot Engine Conditions
- Engine cooling water temperature is monitored at the water pump inlet.
- Excessive heat triggers a "HOT ENGINE-THROTTLE 6 LIMIT" message and limits engine loading (positions 7 or 8).
- This condition remains in effect until temperature returns to a safe limit.
Operating Water Level
- An operating water level instruction plate is next to the water level sight glass.
- It indicates low and full water levels, when the engine is running or stopped.
- Water levels should not be permitted below the specified low mark.
Water Level Switch
- A water level switch (float type) is installed in the cooling system water tank.
- The switch connects to DIO1 input channel 7 labeled NO LWL.
- If the low water level switch is open for 10 seconds while the engine is running, a "LOW ENGINE WATER LEVEL DETECTED” message is displayed and the alarm bell rings for 60 seconds.
- If low water level occurs while engine is shut down, no start is allowed and the same message will be displayed.
Cooling System Pressurization
- Pressurization raises the coolant boiling point, enabling higher engine operating temperatures with minimal coolant loss from boiling.
- This also ensures uniform water flow and minimizes water pump cavitation during transient temperature conditions.
- A pressure cap (located on the water tank fill pipe) relieves excessive pressure (20 psi), preventing cooling system component damage. The pressure cap has a vacuum breaker.
Temperature Gauge
- A color-coded temperature gauge (cold - blue, normal - green, hot - red) is located on the water pump inlet line.
Speed Due to Cold Engine
- If the ETP 1 & 2, detects a temperature below 46°C while the engine is idling, engine speed is increased to TH-2.
- This condition remains until temperature reaches 52°C.
- Once above 52°C the engine speed is reduced back to idle.
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Description
Explore the intricate workings of the water cooling system used in GM locomotives. This quiz covers the flow of coolant, the role of various components, and the continuous cooling process essential for efficient engine operation. Test your knowledge on the layout and function of the system.
