C175 Petroleum Engine Caterpillar

Coolant Pressure Is Low

Usage:

Use this procedure to troubleshoot a low coolant pressure. Also, use this procedure if one of the following event codes is active or logged.

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Table 1
J1939 Code and Description	CDL Code and Description	Comments
109-1 Engine Coolant Pressure : Low - most severe (3)	E2112 (3) Low Engine Coolant Pressure	The engine coolant pressure is lower than expected for an extended period. The code is logged.
109-17 Engine Coolant Pressure : Low - least severe (1)	E2112 (1) Low Engine Coolant Pressure	The engine coolant pressure is lower than expected for an extended period. The code is logged.

Probable Causes

Coolant level
Leaks
Expansion tank (if equipped)
Sensor
Water pump
Heat exchanger
Oil cooler

Recommended Actions

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Table 2
1. Check the Coolant Level Note: 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. A. Check the cooling system for coolant leaks.	Coolant Level	Result: The coolant level is OK. Proceed to Test Step 2. Result: The coolant level is NOT OK. Repair: Determine the cause of the low coolant level. Refer to Troubleshooting, "Coolant Level Is Low" for additional information. If the problem is not resolved, proceed to Test Step 2.
2. Check the Cooling System Hose Routing A. Check the cooling system clamps and hoses to make sure that the clamps and hoses are installed in the proper location 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. If the problem is not resolved, proceed to Test Step 3.
3. Check the Expansion Tank 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. If the problem is not resolved, proceed to Test Step 4.
4. Check the Coolant Pressure Sensor A. Install a mechanical pressure gauge in the coolant jacket near the coolant pressure sensor. B. Start the engine. C. Connect Cat^® Electronic Technician (ET) to the service tool connector. D. Allow the engine to run and record the coolant pressure on the mechanical gauge. E. Check the coolant pressure reading at various engine speeds.	Sensor	Result: The pressure difference between the mechanical gauge and the reading in Cat ET is less than 14 kPa (2 psi). Proceed to Test Step 5. Result: The pressure difference between the mechanical gauge and the reading in Cat ET is greater than 14 kPa (2 psi). Repair: Replace the coolant pressure sensor. If the problem is not resolved, proceed to Test Step 5.
5. Inspect the Water Pump A. Inspect the impeller of the water pump for damage or erosion. B. Ensure that the drive gear is not loose on the drive shaft of the water pump.	Water Pump	Result: The water pump is OK. Proceed to Test Step 6. Result: There was a problem with the water pump. Repair: Repair or replace damaged water pump components. If the problem is not resolved, proceed to Test Step 6.
6. Check the Heat Exchanger for Problems A. Check the cooling fins on the heat exchanger for dirt and for debris. B. Check for sufficient flow and temperature of the cooling water through the heat exchanger. C. Ensure that the size of the heat exchanger is sufficient.	Heat Exchanger	Result: The heat exchanger is OK. Proceed to Test Step 7. Result: A problem with the heat exchanger has been discovered. Repair: If the temperature of the cooling water is too high, determine the cause. Clean the components or replace the heat exchanger. If the problem is not resolved, proceed to Test Step 7.
7. Check the Oil Cooler for a Restriction 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 repair eliminated the problem.

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).