(PCV) System – One Of The Biggest Causes Of Engine Oil Sludge

Clogged (PCV) Valve
Clogged (PCV) Valve

Did you know the most common problem in the (PCV) system; is a plugged up (PCV) valve.

Another problem is a lack of air flow to carry vapors from the crankcase.

So, Without air flow, moisture contamination remains and a sludge buildup is often a result. Furthermore, Operating the engine without adequate ventilation is a leading cause of engine sludge.

An accumulation of fuel and oil varnish deposits and/or sludge inside the valve can restrict or even block the flow of vapors through the (PCV) system. Consequently, A restricted or clogged (PCV) system cannot pull moisture and blowby vapors out of the crankcase. As a result, This can cause engine-damaging sludge to form.

(PCV) Sludge
(PCV) Sludge

May even cause a backup of pressure that may force oil to leak past gaskets and seals. The loss of airflow through the (PCV) system can also cause the air/fuel mixture to run richer than normal. But, The same thing can happen if the pintle inside the valve sticks shut.

If the pintle inside the (PCV) valve sticks open, or the spring breaks; the (PCV) valve may flow too much air and lean out the idle mixture. As a result, causing a rough idle, hard starting and/or lean misfire (which increases emissions and wastes fuel).

Loose Or Leaky Hoses

The same thing can happen if the hose that connects the valve to the throttle body; carburetor or intake manifold pulls loose, cracks, or leaks.

Leaking Hose
Leaking Hose

A loose or leaky hose allows “un-metered” air to enter the engine and upset the fuel mixture; especially at idle where the idle mixture is most sensitive to vacuum leaks.

Incorrect (PCV) Valves

Problems can also occur if someone installs the wrong (PCV) valve for the application. The flow rate of the (PCV) valve is calibrated for a specific engine application. So, Two valves that appear to be identical on the outside may have different pintle valves and springs inside; giving them very different flow rates.

Confirm Correct (PCV) Valve
Confirm Correct (PCV) Valve

A (PCV) valve that flows too much air will lean the air/fuel mixture; while one that flows too little will richen the mixture and increase the risk of sludge buildup in the crankcase.

Basic (PCV) Airflow Testing

Pinch or block off the vacuum hose to the (PCV) valve with the engine idling at operating temperature. The engine idle rpm should typically drop about 50 to 80 rpm before the idle speed corrects itself. If there is no change in idle speed; check the (PCV) valve, hose and breather tube for a restriction or blockage. A greater change would indicate too much airflow through the (PCV) valve. The wrong valve may flow too much air.

Checking For Leaks

Measure the amount of vacuum in the crankcase. With the engine at normal operating temperature, block off the (PCV) breather tube or vent to the engine. Pull out the dipstick and connect a vacuum-pressure gauge to the dipstick tube. Finally, A typical (PCV) system should be pulling about 1 to 3 inches of vacuum in the crankcase at idle.

Vacuum-Pressure Pump
Vacuum-Pressure Pump

A significantly higher vacuum reading, the intake manifold gasket is probably leaking and pulling vacuum on the crankcase. If you see no vacuum, or find a buildup of pressure in the crankcase; the (PCV) system is plugged or is not pulling enough air through the crankcase; to get rid of the blowby vapors.

If the engine has a leaky oil pan; valve cover or intake manifold gasket leak; or leaky crankshaft seals; it will not be able to develop much vacuum in the crankcase; because it is pulling in outside air (which is also unfiltered and can further contaminate the oil).

To find a crankcase air leak; you can lightly pressurize (no more than 1 to 3 psi) the crankcase; with shop air via the dipstick tube or oil filler cap or breather after blocking all the other vents. Do not use any more air pressure than this or you may create leaks where there were no leaks before.

Checking for Leaks
Checking for Leaks

Then use a spray bottle to squirt soapy water around the gasket seams and seals. Finally, If you see bubbles, you have found an air leak (replace the gasket or seal as needed and retest).

Conclusion

Keep in mind that some new models don’t have a valve at all; instead, you’ll find a simple vacuum hose going from the valve cover to an air inlet duct. Others may have a simple restrictor in place. Still, you can check the restrictor, hoses and other components.

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