C7.1 Engines and Generator Sets Caterpillar

Crankcase Breather Ejects Oil

Usage:

C7.1 770

The crankcase breather canister includes a pressure relief valve that prevents a build-up of excessive pressure in the breather canister.

In normal operation of the engine, the pressure relief valve remains closed. If there is evidence of oil staining on the cylinder head behind the breather canister, perform the following procedure to diagnose the fault.

Probable Causes

Breather filter
Breather hoses
Excessive blow-by

Recommended Actions

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Illustration 1	g03758596
Typical breather canister (1) Breather canister cap (2) Filter element (3) Breather canister

Note: The procedures have been listed in order of probability. Complete the procedures in order.

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Table 1
Troubleshooting Test Steps	Values	Results
1. Breather Filter A. Check that filter element (2) is correctly installed and that the element is not damaged. B. Check for restrictions or blockages in breather canister (3). Note: In cold ambient conditions, ice can form in the outlets of the breather canister.	Filter	Result: The filter element (2) is not correctly installed or the element is damaged. Repair: Install the filter element correctly or replace the filter element. Result: There are restrictions or blockages in the breather canister. Repair: Clean the interior of the breather canister. Result: The breather is clean and operating correctly. Proceed to Test Step 2.
2. Breather Hoses A. Make sure that the oil return hose from the breather canister is not pinched or blocked. B. Make sure that the breather outlet hose from the breather canister is not pinched or blocked.	Hoses	Result: One or more of the hoses is pinched or blocked. Repair: Clear the hose or replace the hose. Result: All the hoses are clear. Proceed to Test Step 3.
3. Excessive Blow-by Note: Excessive blow-by increases the flow of fumes through the breather system and can cause the breather filter to block. The pressure relief valve may then open. A. Check the engine for excessive blow-by.	Blow-by	Result: There is excessive blow-by. Repair: Replace the breather filter. Investigate the cause of the excessive blow-by. Refer to Troubleshooting, "Oil Consumption Is Excessive". Result: The blow-by is not excessive. Contact the Dealer Solutions Network (DSN).