C7.1 Engines and Generator Sets Caterpillar

A discharge of condensation from the breather is normal. The discharge is normally clear but can contain soot. Although the discharge can contain oil vapor, any liquid oil must be limited to 0.5 g (0.02 oz) per hour. An oil discharge of more than 0.5 g (0.02 oz) must be investigated.

Probable Causes

• Breather filter

• Engine oil level

• One-way valve

• Excessive blow-by

Recommended Actions

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

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

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: If a new filter element blocks before the service period is completed, the blockage can indicate a fault in the engine. Note: In cold ambient conditions, ice can form in the outlets of the breather canister.	Filter	Result: The filter element (1) 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. Engine Oil Level A. Check the oil level in the engine.	Oil level	Result: The engine oil level is high. Repair: Check for contamination of the oil with fuel or coolant. Refer to Troubleshooting, "Oil Contains Fuel" or Troubleshooting, "Oil Contains Coolant". If the engine oil is not contaminated, remove the excess oil. Result: The engine oil level is correct. Proceed to Test Step 3.

Illustration 2	g03758618
(4) Breather drain hose (5) One-way valve

Table 2

Troubleshooting Test Steps	Values	Results
3. One-way Valve A. Disconnect breather drain hose (4) from one-way valve (5) and then remove the one-way valve from the engine. Refer to Disassembly and Assembly, "Crankcase Breather - Remove". B. Use a suitable cleaning solution to flush the one-way valve. C. Connect a low-pressure air supply breather drain hose side of the one-way valve. The air must flow freely through the valve. D. Connect a low-pressure air supply crankcase side of the one-way valve. The valve must block the airflow.	One-way valve	Result: The one-way valve does not operate correctly. Repair: Install a replacement valve. Refer to Disassembly and Assembly, "Crankcase Breather - Install". Result: The one-way valve operates correctly. Proceed to Test Step 4.
4. Excessive Blow-by Note: Excessive blow-by increases the flow of fumes through the breather system and can cause oil discharge from the fumes disposal tube. 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).