C175 Cooling System Cavitation Test {1350} Caterpillar

Electric Power Generation

C175-16 GEN SET (S/N: WYB1-UP)

Engine

C175-16 (S/N: P6L1-UP)

Introduction

Do not perform any procedure in this Special Instruction until you read and understand the information.

Perform the following procedures to determine if cooling system design is hampering cooling pump efficiency enough to cause aeration. If a minimum coolant pump differential pressure is not achieved, cavitation will develop. Cavitation can cause overheating throughout the operating range of the engine. Cavitation can also severely damage cooling system components. Once cavitation begins, erosion of components causes a continuous degradation of the cooling system efficiency. As cooling system efficiency decreases, cavitation and erosion escalates causing engine overheating and component failure.

The following procedure provides the information necessary to test the jacket water cooling system and the Separate Circuit Aftercooler (SCAC) system.

First, the procedure will be used to evaluate the jacket water cooling system for cavitation. During this test, the temperature sensor for the water pump outlet will be rewired to the Electronic Control Module (ECM) for temperature monitoring purposes. After you test the jacket water cooling system, the original wiring will be restored and the SCAC will be tested using the same procedure. You may want to make a separate copy of the log and graph sheet and the data tables for each of the cooling systems.

The first section of this procedure defines engine and cooling system pre-checks and setup of the required instrumentation.

The second section provides information necessary to warm the engine correctly prior to measuring the operating conditions of the cooling system. In this section, you will heat the engine throughout the temperature range of the system and record the necessary data.

The next section provides instruction for the necessary calculations and analysis of the test results.

The final section provides some possible causes of cooling system problems

Note: For valid test results to be obtained, mechanical pressure gauges with similar accuracy of the gauge listed above must be used. Also, the gauges must be installed in the ports as instructed in the procedure below.

Prepare the Jacket Water Cooling System for Testing

Perform the following steps to prepare the engine for testing:

Show/hide table

Illustration 1	g02727287
Motor cover for the electronic thermostat (1) Shaft extension (2) 12-pin harness connector

1. In order to block the thermostat passage to the engine, disconnect 12-pin harness connector (2) at the Temperature Control Module (TCM). Removing power from the TCM will allow for manual control of the electronic thermostat during the test. Use shaft extension (1) to position the piston manually at the end-stop in order to close the thermostat. Turn the shaft in the counterclockwise direction.

2. Ensure that the cooling system is filled with coolant.

3. Ensure that the engine can be controlled at the rated speed for an extended period.

4. Equip the radiator with a vented radiator cap that has a vent line. The line must be long enough to drain into a discharge collection bucket without kinking.

5. Check and fill the engine crankcase to the recommended level.

6. Ensure that the radiator is in a level position.
   Show/hide table

   Illustration 2	g02726661
   Locations for the test ports and the coolant temperature sensor for the jacket water cooling system (3) Test port for the inlet of the jacket water cooling pump (4) Test port for the outlet of the jacket water cooling pump (5) Coolant temperature sensor

7. Rewire the jacket water coolant temperature sensor to the ECM terminal locations that are for the aftercooler coolant temperature sensor. The status of the SCAC pump outlet temperature will be monitored using Caterpillar Electronic Technician (ET) during the test to monitor the pump outlet temperature.

   1. Fabricate two jumper wires that are long enough to connect the circuit wiring for the jacket water coolant temperature sensor to the P2 ECM connector. Crimp connector sockets to each end of both jumper wires.

   2. Install one end of each of the jumper wires into a 230-4011 Connector Plug As.

   3. Disconnect the harness connector from the coolant temperature sensor (5) at the pump outlet for the cooling system. Install the connector for the jumper harness onto this coolant temperature sensor.
      Show/hide table

      Illustration 3	g02727276
      Terminal locations at the P2 ECM connector for the SCAC coolant temperature sensor (P2-13) SCAC coolant temperature (P2-92) Analog return

   4. Use a wire removal tool to remove the wire from terminal location P2-13 (SCAC coolant temperature) at the ECM connector. Install the loose end of the jumper wire for terminal 1 (signal) at the coolant temperature sensor into P2-13.

   5. Use a wire removal tool to remove the wire from terminal location P2-92 (analog return) at the ECM connector. Install the loose end of the jumper wire for terminal 2 (return) at the coolant temperature sensor into P2-92.

      Note: Removing the wire from the analog return at P2-92 will not affect other analog sensors on the circuit. Redundant returns are spliced into this circuit that are wired to P1-5 and P1-18.

8. Install the pressure gauges at the inlet and the outlet of the coolant pump.

   1. Remove the plugs from test ports (3) and (4).

   2. Use a 5C-7617 Reducing Bushing to reduce the port opening to the correct size for the gauges.

   3. Install a 8T-0862 Pressure Gauge into each of the ports.

Collect Cooling System Data

During the following procedure, data will be collected and recorded in Table 2. Pump rise pressures will be calculated from the collected data. Data points that correspond to the pump rise pressures will be plotted on the "Cavitation Test Log and Graph" shown in Illustration 4. This information will be used to in the next section to evaluate the cooling system.

A space has been provided to record the engine information, the technician name, and the test date on each of the data sheets.

Perform the following test procedure to gather data during the engine conditions that may produce cavitation.

Note: As a cooling system requirement, a minimum pressure of −6 kPa (−0.87 psi) is required at the inlet of the water pump at all times.

Use the following Table to record the individual pump pressures at each temperature designation:

Illustration 4	g02726414
Cavitation test log and graph worksheet (X) Coolant temperature ( ° C (° F)) (Y) Pump rise (ΔP ( kPa (psi)))

Follow these instructions closely in order to produce accurate results:

1. Start the engine. Allow the engine to idle for 5 minutes.

2. During this time, check the barometric pressure. Record this value in the space provided in Table 3.

3. Recheck the coolant level of the cooling system. Add coolant as necessary.

   Note: There must be no air left in the top of the radiator tank in order to perform this procedure correctly.

4. Install the vented cap with vent line onto the radiator. Place the loose end of the vent line into a discharge bucket.

   Ensure that the loose end of the vent line does not become submersed in overflow coolant at any time during the entire procedure.

   Also, ensure that the vent line is not allowed to kink during the entire testing procedure.

5. Maintain a constant rated engine speed throughout the entire test procedure. Variations in engine speed during this procedure may give a false indication of a problem in the cooling system.

6. Begin to record the inlet pump pressure and the outlet pump pressure at 46° C (115° F) on the worksheet provided.

   Ensure that the minimum requirement of −6 kPa (−0.87 psi) is available at the water pump inlet. If this specification is not met, discontinue the test and perform the necessary repairs.

7. Slowly raise the coolant temperature by placing a piece of cardboard on the front face of the radiator, or by electronically modulating the cooling fans.

   Note: Adjust the cardboard, or modulate the fan, so the rate of increase for the coolant temperature is approximately 2.7° C (5° F) every 2 to 3 minutes.

   The objective is to raise the coolant temperature slowly in order to record meaningful pump differential pressures.

8. Follow the sampling interval that is defined in Table 2:

   For the range of coolant temperatures from 46° C (115° F) to 82° C (180° F), log each point at 5.4° C (10° F) intervals.

9. At 82° C (180° F), begin log differential pressures at intervals of 1° C (2° F).

   Exercise special care when you increase the coolant temperature and record the pump pressures in the range of 85° C (185° F) to 99° C (210° F). This temperature range is where the fastest reduction of pump pressure rise occurs.

10. Continue to raise the coolant temperature and record data. Proceed until the coolant temperature reaches 99° C (210° F) or the differential pressure drops to a minimum of 30% of the pump rise at 49° C (120° F). End the testing at this time.

    If the above conditions cannot be reached, end the test at the maximum coolant temperature that can be reached.

11. When one of the above conditions is met, reduce the engine speed. Allow the coolant temperature to drop below 82° C (180° F) prior to stopping the engine.

12. Once the testing is complete, restore the cooling system and the wiring to the original configuration.

13. On Table 2, subtract each recorded outlet pressure from the corresponding inlet pressure and record the result. Use the graph that is provided to plot each point as a differential pressure.

Evaluate the Cooling System for Cavitation

To evaluate the cooling system for cavitation, a series of points will be read from the graph and used to complete the differential data.

From the plotted data, a calculated pump rise will be overlaid on the graph and a cavitation temperature for the cooling system will be established. An example of the resulting overlay appears on the example plot that is shown in Illustration 5.

Illustration 5	g02727217
Example plot of cooling system data (a-a) Cooling system performance curve (b-b) Lower limit of acceptable pump rise pressure (c) Point of acceptable pump rise pressure (d) Temperature at the lower limit of the acceptable pump rise pressure (X) Coolant temperature ( ° C (° F)) (Y) Pump rise (ΔP ( kPa (psi)))

1. Calculate the lower limit of acceptable pump rise for the cooling system (line b-b).

   1. First, subtract the percent of allowable pump rise loss acceptable for the engine model from 100 percent.

      Note: The percent of allowable pump rise loss acceptable for C175 Gen Set Engines is a maximum of 10 percent.

   2. Multiply the resulting decimal value (numeric percentage) by the pump rise value recorded at 49° C (120° F) on (plot a-a).

   3. The result is the lower limit of acceptable pump rise. Record the result in Table 3.

   4. Use the result to draw line (b-b) on the graph. Extend the line across plot (a-a). This line will establish the lower limit of acceptable pump rise.

      Refer to Illustration 5 as an example.

      Note: By drawing a vertical line down to the pump outlet temperature axis, the cavitation temperature for the cooling system is revealed.

2. Read the pump rise pressure at point (c). This point is the cavitation requirement of the cooling system. Record this pump rise pressure in the proper place in Table 3.

3. Determine the cavitation temperature (Tc) for the cooling system:

   1. Reference the Technical Marketing Information (TMI) data for the engine to obtain the following values:

      • Engine heat rejection (BTU/min)

      • Coolant pump flow (gpm)

   2. Calculate Tc by first dividing the engine heat rejection value by the coolant pump flow. Subtract the resulting temperature from 210 (degrees fahrenheit).

      The resulting temperature is the uncorrected cavitation temperature (Tc) for the engine cooling system.

      Record the uncorrected cavitation temperature (Tc) in the proper place in Table 3.

   3. Correct the cavitation temperature (Tc) by adjusting for the site barometric pressure that was recorded earlier in Table 2:

      Add 1 degree to Tc for each 3.4 kPa (1 inch mercury) that the site barometric pressure is below 100 kPa (29.60 inch mercury).

      Subtract 1 degree to Tc for each 3.4 kPa (1 inch mercury) that the site barometric pressure is above 100 kPa (29.60 inch mercury).

      Record the corrected cavitation temperature (Tc) in the proper place in Table 3.

4. Locate the pump rise pressure on the plot of engine cooling system performance (plot a-a) at the corrected value of Tc.

5. This point defines the actual pump rise for the cooling system that is being tested. Record the pump rise at the corrected Tc in the space provided in Table 3.

6. Compare the resulting pump rise with the cavitation requirement that was recorded earlier. Record the cavitation test results in the space provided in Table 3.

   If the resulting pump rise for the cooling system exceeds the requirement, the cooling system performance is acceptable.

   If the resulting pump rise for the cooling system is less than the requirement, there is a problem in the cooling system. Check the information provided in "Possible Causes of Cooling System Cavitation" for information related to cooling system problems. Perform the necessary repairs.

Possible Causes of Cooling System Cavitation

Check for the following problems if your cooling system does not meet the cavitation requirements.

Check for restrictions in the cooling system:

• Check that the cooling system piping is the correct size for the requirements of the system.

• Check for excessive routing of the cooling system piping. Excessively long routings will increase the resistance to coolant flow.

• Check for an excessive number of bends in the piping of the cooling system,

• Check for severe bends in the cooling system piping.

• Check that the bottom tank of the radiator is not too shallow for unrestricted flow through the tank. Ensure that the radiator design is correct for your application.

• Check if additional components in the radiator tanks, such as oil coolers, are causing excessive restriction.

• Check that the radiator contains the correct number and size of tubing for the cooling system flow requirements.

• Check that any baffles in the tank of the radiator or heat exchangers are not leaking or loose in the tank.

Once the problem is located, perform the necessary repairs.

Prepare the SCAC System for Testing

Perform the following steps to prepare the SCAC system for testing:

1. Block any open thermostats to the radiator.

2. Ensure that the cooling system is filled with coolant.

3. Ensure that the engine can be controlled at the rated speed for an extended period.

4. Equip the radiator with a vented radiator cap with a vent line. The vent line must be long enough to drain into a discharge collection bucket without kinking.

5. Check and fill the engine crankcase to the recommended level.

6. Ensure that the radiator is in a level position.

Show/hide table

Illustration 6	g06316165
Locations for the test ports and sensors for the SCAC cooling system (6) Coolant temperature sensor (7) Coolant pump outlet pressure sensor (8) Test port for the outlet of the SCAC cooling pump (9) Test port for the inlet of the SCAC cooling pump

1. Install the pressure gauges at the inlet and the outlet of the SCAC coolant pump:

   1. Remove the plugs from test ports (8) and (9).

   2. Use a 5C-7617 Reducing Bushing to reduce the port opening to the correct size for the gauges.

   3. Install a 8T-0862 Pressure Gauge into each of the ports.

2. Proceed to "Collect Cooling System Data" and follow the documented procedure.