C13, C15, and C18 Engines Troubleshooting – Exhaust System Contains Oil

Probable Causes


  • Failed turbocharger seals 
  • Worn valve guide seals or faulty valve guide seals 
  • Worn valve guides 
  • Worn piston rings 
  • Extended idle times 

Recommended Actions

Note: Replacing the DOC and DPF is recommended if there is oil in the exhaust.

Table 1
Troubleshooting Test Steps Values Results
1. Failed Turbocharger Seals

A. Check the inlet manifold and the exhaust manifold for oil.

Turbo seals Result: Oil is present in the inlet or exhaust manifold.

Replace the turbocharger. Verify the repair.

Result: Oil is not present in the inlet or exhaust manifold.

Proceed to Test Step 2.

2. Worn Valve Guide Seals or Faulty Valve Guide Seals

A. Inspect the valve guide seals for wear and for damage.

Valve guide seals Result: The valve guide seals are damaged.

Replace the valve guide seals. Verify the repair.

Result: The valve guide seals are not damaged.

Proceed to Test Step 3.

3. Worn Valve Guides

A. Inspect the valve guides for wear. Refer to the Specification manual for the maximum permissible wear of the valve guides.

Valve guides Result: The valve guides are worn.

If necessary, recondition the cylinder head. Verify the repair.

Result: The valve guides are not worn.

Proceed to Test Step 4.

4. Worn Piston Rings

A. Piston rings that have excessive wear can cause too much pressure in the crankcase. The additional pressure in the crankcase will cause more than the normal amount of crankcase blowby from the crankcase breather. Use the following service tools, along with Software License, NETG5044:

1. 285-0900 Blowby Tool Gp (SMALL ENGINE)
2. 348-5430 Multi-Tool Gp

B. Inspect piston rings

Piston rings Result The piston rings are worn.

Replace the piston rings. Verify the repair.

Result The piston rings are not worn.

Proceed to Test Step 5.

5. Extended Idle Times

A. Extended idle times will allow oil to pass into the exhaust system.

Idle times Result The idle times are extensive.

Reduce the idle times.

Complete the procedure in the order in which the steps are listed.

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).


Posted in C18

Leave a Reply

Your email address will not be published. Required fields are marked *