77319 Mercruiser HEAT EXCHANGER(MCM)

Probable Causes
Low Coolant Level and/or Coolant Leakage
Coolant Temperature Sensor
Water Temperature Regulator
Radiator
Engine Cooling Fan
Coolant Pump
Cylinder Head GasketRecommended Actions
Note: The procedures have been listed in order of probability. Complete the procedures in order.
Table 2
Troubleshooting Test Steps Values Results
1. Check the Engine Coolant Level.
A. Inspect the coolant level.
Engine Coolant Level
Result: The engine coolant level is OK.
Proceed to Test Step 2.
Result: The engine coolant level is not OK.
Repair : Check the cooling system for leaks. Refer to Troubleshooting, "Coolant Level is Low" for additional information. Repair any leaks immediately.
If the problem is not resolved, proceed to Test Step 2.
2. Check the Cooling System
A. Refer to Systems Operation/Testing and Adjusting, "Cooling System - Check (Overheating)"
Cooling System
Result: The cooling system is ok..
Proceed to Test Step 3.
Result: The cooling system is not ok.
Repair : Make the appropriate repairs.
If the problem is not resolved, proceed to Test Step 3.
3. Coolant Temperature Sensor and/or the Circuit
A. Check the reading of the coolant temperature on Cat ET. The temperature should rise steadily as the engine is warmed. Ensure that the temperature is reasonable.
Coolant Temperature Sensor
Result: The temperature sensor is working properly.
Proceed to Test Step 4.
Result: The temperature sensor is not working properly.
Repair : Troubleshoot the circuit and the coolant temperature sensor. Refer to Troubleshooting, "Sensor Signal (Analog, Passive) - Test".
If the problem is not resolved, proceed to Test Step 4.
4. Water Temperature Regulator
A. Pressure-test the cooling system. Refer to Systems Operation/Testing and Adjusting for the correct procedure.
B. Check that the seating surfaces the radiator cap are clean and undamaged.
C. Check operation of the water temperature regulator. Refer to Systems Operation/Testing and Adjusting, "Water Temperature Regulator - Test"
Temperature Regulator
Result:The water temperature regulator is operating properly.
Proceed to Test Step 5.
Result: The water temperature regulator is not operating properly.
Repair : Clean the components and/or replace the components.
If the problem is not resolved, proceed to Test Step 5.
5. Radiator
A. Check the radiator fins for dirt, debris, and/or damage.
B. Check for collapsed hoses and/or other restrictions.
C. Check the radiator for internal blockage.
Radiator
Result: The radiator fins are not damaged and the radiator does not have an internal blockage.
Proceed to Test Step 6.
Result: The radiator fins are damaged.
Repair : Remove any dirt and/or debris and straighten any bent fins.
Result: The radiator has internal blockage.
Repair : Remove the blockage.
If the problem is not resolved, proceed to Test Step 6.
6. Inspection of the Water Pump
A. Inspect the impeller of the water pump for damage and/or erosion.
B. Make sure that the drive gear is not loose on the drive shaft of the water pump.
Water Pump
Result: The water pump is operating correctly.
Proceed to Test Step 7.
Result: The water pump is not operating correctly.
Repair : If necessary, replace the water pump. Refer to Disassembly and Assembly for the correct procedure.
If the problem is not resolved, proceed to Test Step 7.
7. Internal Coolant Leak
Refer to Testing and Adjusting, Cooling System - Test.
Coolant Leak
Result: There is a coolant leak.
Make the necessary repairs and return to service.
If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).