65941 Mercruiser STUD, SWITCH BOX AND COVER ATTACHING

Table 1
Diagnostic Trouble Codes for Low Coolant Pressure
J1939 Code Code Description
(code descriptions may vary) Comments
109-17 Engine Coolant Pressure : Low - least severe (1) The engine coolant pressure is lower than expected for an extended period. The code is logged.
109-18 Engine Coolant Pressure : Low - moderate severity (2) The engine coolant pressure is lower than expected for an extended period. The code is logged.
Table 2
Troubleshooting Test Steps Values Results
1. Verify the Coolant Level
A. Verify that the coolant is filled to the correct level. If the coolant level is too low, air will get into the cooling system. Air in the cooling system will cause a reduction in coolant flow and pressure.
B. Check the cooling system for coolant leaks.
C. Check the cooling system for combustion gases.
Coolant Level
Result: The coolant level is correct.
Proceed to Test Step 2.
Result: The coolant level is not correct or combustion gases are present.
Repair: Determine the cause of the low coolant level. Refer to Troubleshooting, "Coolant Level Is Low" and Coolant Temperature Is High. Verify that the problem has been corrected.
2. Check the Cooling System Hose Routing
A. Check that the cooling system clamps and hoses are installed in the correct locations and the clamps are tight.
B. Ensure that there are no kinks or tight bends that may cause excessive restriction.
C. Check to make sure that the hoses are routed correctly.
Leaks or Kinks
Result: The coolant clamps and hoses are installed properly.
Proceed to Test Step 3.
Result: The coolant clamps and hoses are not installed properly.
Repair: Repair or replace the damaged cooling system component. Verify that the problem has been corrected. Return the unit to service.
3. Check the Expansion Tank (if equipped)
A. Check the shunt line for a restriction. A restriction of the shunt line from the expansion tank to the inlet of the jacket water pump will cause a reduction of water pump efficiency.
B. Inspect the expansion tank for a restriction that blocks the port to the shunt line.
Note: The expansion tank may be integrated into the design of the radiator top tank and may not be separate.
Shunt Line
Result: The shunt line is properly installed and there are no restrictions.
Proceed to Test Step 4.
Result: The shunt line is not properly installed or there are restrictions.
Repair: Install the shunt line correctly or replace the line if necessary. Remove any restrictions that are found.
Verify that the problem has been corrected. Return the unit to service.
4. Check the Coolant Pressure Sensor For Accuracy
A. Install a mechanical pressure gauge in the coolant jacket near the coolant pressure sensor.
B. Start the engine.
C. Connect to the engine ECM using the electronic service tool.
D. Allow the engine to run and record the pressure on the mechanical gauge.
E. Check the pressure reading at various engine speeds.
Coolant Pressure Sensor
Result: The pressure difference between the mechanical gauge and the reading on the electronic service tool is less than 14 kPa (2 psi).
Proceed to Test Step 5.
Result: The pressure difference between the mechanical gauge and the reading on the electronic service tool is greater than 14 kPa (2 psi).
Repair: Replace the coolant pressure sensor.
Verify that the problem has been corrected. Return the unit to service.
5. Check the Water Pump
A. Remove the water pump and check for a damaged or loose impeller, or a restriction in the water pump inlet or outlet ports.
Damaged Impeller
Result: The water pump impeller is not damaged or loose and there are no restrictions.
Proceed to Test Step 6.
Result: The water pump impeller is damaged or loose, or there are restrictions.
Repair: Replace the water pump.
Verify that the problem has been corrected. Return the unit to service.
6. NRS Cooler Leak
A. Check the NRS cooler for leaks. Refer to Testing and Adjusting, "Exhaust Cooler (NRS) - Test".
NRS Cooler
Result: The NRS cooler does not have a leak.
Proceed to Test Step 7.
Result: The NRS cooler has a leak.
Repair: Replace the NRS cooler. Refer to the Disassembly and Assembly manual for the related procedure.
Verify that the problem has been corrected. Return the unit to service.
7. Check the Radiator
A. Check the radiator for a restriction. Check internally for dirt, debris, or deposits on the radiator core.
Restrictions
Result: There were deposits or restrictions in the radiator.
Repair: Clean or replace the radiator.
Verify that the problem has been corrected. Return the unit to service.
Result: There were no deposits or restrictions in the radiator.
Proceed to Test Step 8.
8. Check the Oil Cooler
A. Check the inlet side of the oil cooler for debris or blockage.
Restrictions
Result: There was debris or restrictions in the oil cooler.
Repair: Clean or replace the oil cooler.
Verify that the problem has been corrected. If the problem is still present, contact the Dealer Solutions Network (DSN).
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).