SHAFT ASSEM. 4N4870 - Caterpillar

Probable Causes
Incorrect maintenance intervals and/or incorrect oil
Contaminated engine oil
Leaks in air intake system
Dirt in fuel
Low oil pressureRecommended Actions
Note: The procedures have been listed in order of probability. Complete the procedures in order.
Table 1
Troubleshooting Test Steps Values Results
1. Incorrect Maintenance Intervals and/or Incorrect Oil
A. Use engine oil that is recommended and change the engine oil at the interval that is recommended by the engines Operation and Maintenance Manual.
Maintenance intervals
Result: The engine oil was not changed at the interval that is recommended by the Operation and Maintenance Manual.
Repair: Use the recommended grade of oil.
Change the engine oil at the interval that is recommended. Repair or replace any damaged parts.
Result: The engine oil was changed at the interval that is recommended by the engines Operation and Maintenance Manual.
Proceed to Test Step 2.
2. Contaminated Engine Oil
A. Obtain an oil analysis. The analysis will identify oil contamination.
B. Check the oil filter bypass valve.
Note: If the oil filter bypass valve is open, the oil will not be filtered.
Contamination
Result: The oil is contaminated.
Repair: Determine the reason for any contamination of the engine oil and make the necessary repairs. Drain the crankcase and refill the crankcase with clean engine oil. Install new engine oil filters. Refer to the engines Operation and Maintenance Manual.
Result: The oil filter bypass valve is open.
Repair: Replace the oil filter element. Refer to the Operation and Maintenance Manual.
Check the oil filter bypass valve for a weak spring or for a broken spring. If the spring is broken, replace the spring. Verify that the oil bypass valve is operating correctly.
Result: The oil is not contaminated.
Proceed to Test Step 3.
3. Leaks in Air Intake System
Note: A leak in the air intake system may allow unfiltered air into the engine.
A. Inspect the air intake system for streaks which may indicate a leakage of unfiltered air. Inspect all of the gaskets and the connections. Refer to Systems Operation, Testing, and Adjusting, "Air Inlet and Exhaust System" for more information.
Air leak
Result: There are air leaks.
Repair: Repair any leaks.
Result: There are no air leaks.
Proceed to Test Step 4.
4. Dirt in Fuel
A. Remove the fuel filters. Inspect the fuel filters for contamination.
Note: Contaminants in the fuel such as hydrogen sulfide and sulfur can lead to the formation of acids in the crankcase.
B. Obtain a fuel analysis.
Fuel and fuel filters
Result: The fuel has contamination.
Repair: Determine the cause of any contamination and make the necessary repairs.
Install new fuel filters. Refer to the Operation and Maintenance Manual.
Result: The fuel is not contaminated.
Proceed to Test Step 5.
5. Low Oil Pressure
Note: Engine oil that is contaminated with another liquid can cause low engine oil pressure. High engine oil level can be an indication of contamination.
A. Obtain an analysis of the engine oil.
B. Check the inlet screen on the suction tube and remove any material that may be restricting engine oil flow.
Note: The inlet screen of the suction tube for the engine oil pump can have a restriction. This restriction will cause cavitation and a loss of engine oil pressure.
Note: When some components of the