C7 and C9 Industrial Engines Troubleshooting – Oil Temperature Is High

Probable Causes


  • Oil specifications 
  • Engine oil temperature reading 
  • Engine oil cooler bypass valve 
  • High coolant temperature 
  • Engine oil cooler 

Recommended Actions

Table 1
Troubleshooting Test Steps Values Results
1. Oil Specifications

A. Inspect the engine oil level.

B. Check the condition of the engine oil.

Oil Specifications Result: Engine oil is at the correct level and in the proper condition.

Proceed to Test Step 2.

Result: Engine oil is not at the correct level and is not in proper condition.

Repair: Add the correct engine oil.

For information on oil specifications and/or information on oil analysis, refer to the Operation Maintenance Manual.

2. Engine Oil Temperature Reading

A. Compare the engine oil temperature reading from the Caterpillar Electronic Technician (ET) to the temperature from a 6V-9130 Temperature Adapter.

B. Verify that the readings are close.

Engine Oil Result: The engine oil temperature reading is correct.

Proceed to Test Step 3.

Result: The engine oil temperature reading is not correct.

Repair: Make repair and return to service.

3. Engine Oil Cooler Bypass Valve

A. Clean the engine oil cooler bypass valve and inspect the engine oil cooler bypass valve.

B. Clean the bore for the valve.

C. Ensure that the bypass valve is not stuck in the open position.

Bypass Valve Result: The engine oil cooler bypass valve is clean and properly working.

Proceed to Test Step 4.

Result: The engine oil cooler bypass valve is not properly working after cleaning.

Repair: Replace the bypass valve if necessary and refer to Disassembly and Assembly.

4. High Coolant Temperature

A. Check for an elevated engine coolant temperature.
A high coolant temperature can cause the engine oil temperature to increase out of specifications.

Coolant Temperature Result: The engine coolant temperature is at the proper temperature.

Proceed to Test Step 5.

Result: The engine coolant temperature is elevated.

Repair: Troubleshoot any codes before continuing with this procedure.
Refer to Troubleshooting, “Coolant Temperature is High” for information related to troubleshooting an elevated coolant temperature.

5. Engine Oil Cooler

A. Check the engine oil cooler for damage and plugging.

B. Inspect for a restriction in the passages for engine oil in the engine oil cooler.

Engine Oil Cooler Result: The engine oil cooler is plugged or damaged.

Repair: Clean the engine oil cooler core or replace the engine oil cooler core.
Verify that the repair eliminated the problem.


Posted in C7

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