3056E Industrial Engine Caterpillar

Measuring Engine Oil Pressure

4C-4890 Hydraulic Test Group can be used in order to test the pressure of the lubrication system.

The engine oil pressure can also be checked using Caterpillar Electronic Technican (Cat ET). Refer to Troubleshooting for information on the use of Cat ET.

1. Remove the engine oil temperature sensor.

2. Install the 4C-4890 Hydraulic Test Fitting Gp into the port in the engine side cover.

3. Start the engine and run the engine. Use SAE 15W40 oil. Refer to Operation and Maintenance Manual, "Engine Oil" for the recommendations of engine oil.

Note: There is a direct correlation between engine speed and engine oil pressure.

4. Record the value of the engine oil pressure when the engine is at operating temperature 100 °C (212 °F).

   Minimum engine oil pressure at high idle is 280 kPa (40 psi). Minimum engine oil pressure at low idle is 150 kPa (22 psi).

5. Compare the recorded engine oil pressure with the oil pressure indicators on the instrument panel and the engine oil pressure that is displayed on Cat ET.

6. An engine oil pressure indicator that has a defect or an engine oil pressure sensor that has a defect can give a false indication of a low oil pressure or a high oil pressure. If there is a notable difference between the engine oil pressure readings, make necessary repairs.

7. If the engine oil pressure is too low, refer to " Low Oil Pressure".

8. If the engine oil pressure is too high, refer to "High Oil Pressure".

Low Oil Pressure

The following conditions will cause low oil pressure.

• Engine oil level is low. Refer to Step 1.

• Engine oil is contaminated. Refer to Step 2.

• The engine oil bypass valves are open. Refer to Step 3.

• The engine lubrication system is open. Refer to Step 4.

• The oil pickup tube has a leak or a restricted inlet screen. Refer to Step 5.

• The engine oil pump is faulty. Refer to Step 6.

• Engine Bearings have excessive clearance. Refer to Step 7.

1. Check the engine oil level in the crankcase. The oil level can possibly be too far below the oil pump supply tube. If the engine oil level is low, add engine oil in order to obtain the correct engine oil level. Refer to Operation and Maintenance Manual, "Engine Oil" for the recommendations of engine oil.

2. Engine oil that is contaminated with fuel or coolant will cause low engine oil pressure. High engine oil level in the crankcase can be an indication of contamination. Determine the reason for contamination of the engine oil and make the necessary repairs. Replace the engine oil with the approved grade of engine oil. Refer to Operation and Maintenance Manual, "Engine Oil" for the recommendations of engine oil.

Show/hide table

NOTICE
Caterpillar oil filters are built to Caterpillar specifications. Use of an oil filter not recommended by Caterpillar could result in severe engine damage to the engine bearings, crankshaft, etc., as a result of the larger waste particles from unfiltered oil entering the engine lubricating system. Only use oil filters recommended by Caterpillar.

3. If the engine oil bypass valves are held in the open position, a reduction in the oil pressure can be the result. This may be due to debris in the engine oil. If the engine oil bypass valves are stuck in the open position, remove each engine oil bypass valve and clean each bypass valve in order to correct this problem. You must also clean each bypass valve bore. Install new engine oil filters. New engine oil filters will prevent more debris from causing this problem. For information on the repair of the engine oil bypass valves, refer to Disassembly and Assembly, "Engine Oil Filter Base - Disassemble". Also, refer to Specifications, "Engine Oil Bypass Valve" for the correct operating pressure and other information.

4. An oil line or an oil passage that is open, broken, or disconnected will cause low engine oil pressure. An open lubrication system could be caused by a piston cooling jet that is missing or damaged. Determine the reason for an open lubrication system of the engine and make the necessary repairs.

   Note: The piston cooling jets direct engine oil toward the bottom of the piston in order to cool the piston. This also provides lubrication for the piston pin. Breakage, a restriction, or incorrect installation of the piston cooling jets will cause seizure of the piston.

5. The inlet screen of the oil pickup tube for the engine oil pump can have a restriction. This restriction will cause cavitation and a loss of engine oil pressure. Check the inlet screen on the oil pickup tube and remove any material that may be restricting engine oil flow. Low engine oil pressure may also be the result of the oil pickup tube that is drawing in air. Check the joints of the oil pickup tube for cracks or a damaged O-ring seal. Remove the engine oil pan in order to gain access to the oil pickup tube and the oil screen. Refer to Disassembly and Assembly, "Engine Oil Pan - Remove and Install" for more information.

6. Check the following problems that may occur to the engine oil pump.

   1. Air leakage in the supply side of the oil pump will also cause cavitation and loss of oil pressure. Check the supply side of the oil pump and make necessary repairs. For information on the repair of the engine oil pump, refer to Disassembly and Assembly, "Engine Oil Pump - Remove".

7. Excessive clearance at engine bearings will cause low engine oil pressure. Check the engine components that have excessive bearing clearance and make the necessary repairs.

High Oil Pressure

High oil pressure can be caused by the following conditions.

• The spring for the oil pressure relief valve is installed incorrectly.

• The plunger for the oil pressure relief valve becomes jammed in the closed position.

• Excessive sludge exists in the oil which makes the viscosity of the oil too high.

Engine oil pressure will be high if the engine oil bypass valves become stuck in the closed position and the engine oil flow is restricted. Foreign matter in the engine oil system could be the cause for the restriction of the oil flow and the movement of the engine oil bypass valves. If the engine oil bypass valves are stuck in the closed position, remove each bypass valve and clean each bypass valve in order to correct this problem. You must also clean each bypass valve bore. Install new engine oil filters. New engine oil filters will prevent more debris from causing this problem. For information on the repair of the engine oil filter bypass valve, refer to Disassembly and Assembly, "Engine Oil Filter Base - Disassemble".