Also, the PCV valve has internal parts that develop wear and tear; that a simple cleaning will not fix. Finally, proper maintenance of the Positive Crankcase Ventilation PCV system, will help reduce overall vehicle emissions. So, this part may be small and not cost much, But plays a huge role, in a healthy running engine. So, you should never have a fuel smell in your vehicle. Consequently, if you smell fuel this could be a sign of a fuel leak. A fuel leak can be dangerous to drive with because; […].
Another problem, is a lack of air flow, to carry vapors from the crankcase. Because, without air flow, […]. The function of the evaporative emission control system EVAP , is to trap and store evaporative fuel emissions. The EVAP system therefore, totally eliminates fuel vapors, as a source of air pollution. But, sealing the fuel […].
Most of the images displayed are of unknown origin. We do not intend to infringe any legitimate intellectual right, artistic rights or copyright. The oil drain line from these components ensures that gas leaking past the turbocharger shaft and the piston rings of an air compressor will pass into the engine crankcase contributing to blowby.
Blowby amounts vary greatly depending on engine design, temperature operating conditions and engine wear. Some of these estimates are outlined in Table 1. Dealing with blow by, even the normal amount, has taken on several different forms over the years. In some cases and even recently it was simply vented to the atmosphere, known as open crankcase ventilation, which, on a boat means into the engine room.
This type of crankcase ventilation hose usually snakes down the side of an engine to the bilge where it ideally emits just a small amount of gas, oil and water vapor. This crankcase ventilation system installation represents good intentions with poor execution. Oil vapor that is coalesced inside the black canister must be plumbed to drain back to the oil pan. In general, however, for an engine whose rings are not worn, the level of contamination is relatively minor.
Most crankcase ventilation systems include baffles through which the gasses and vapors must pass, capturing some of the oil vapor, returning it to the crankcase.
As valuable as they are, after-market crankcase ventilation systems are only effective when properly installed. The quality and effectiveness of crankcase ventilation systems ranges from primitive, the hose leading into the bilge, to sophisticated, serviceable, monitorable baffled chambers. The goals of the latter closed system are multiple. In addition to making the engine room greasy or sooty, these byproducts are unfriendly to the environment. Telltale signs of excess crankcase pressure are often visible if you know what to look for.
In some cases, a seemingly simple oil leak is in fact the result of pressure pushing oil past seals or gaskets. Chronic crankcase or valve cover leaks in that reappear after they have been repaired are also a sign of potential excess pressure. Disabling or disconnecting the PCV system can also allow moisture to accumulate in the crankcase, which will reduce oil life and promote the formation of engine-damaging sludge.
The flow rate of a PCV valve is calibrated for a specific engine application. For the system to function normally, therefore, the PCV valve must adjust the flow rate as operating conditions change.
When the engine is off, the spring inside the valve pushes the pintle shut to seal the crankcase and prevent the escape of any residual vapors into the atmosphere. When the engine starts, vacuum in the intake manifold pulls on the pintle and sucks the PCV valve open. The pintle is pulled up against the spring and moves to its highest position.
But the tapered shape of the pintle does not allow maximum flow in this position. Instead, it restricts flow so the engine will idle smoothly.
The same thing happens during deceleration when intake vacuum is high. The pintle is pulled all the way up to reduce flow and minimize the effect of blowby on decel emissions. When the engine is cruising under light load and at part throttle, there is less intake vacuum and less pull on the pintle. This allows the pintle to slide down to a mid-range position and allow more airflow.
Under high load or hard acceleration conditions, intake vacuum drops even more, allowing the spring inside the PCV valve to push the pintle valve even lower to its maximum flow position. If blowby pressure builds up faster than the PCV system can handle it, the excess pressure flows back through the breather hose to the air cleaner and is sucked back into the engine and burned. In the event of an engine backfire, the sudden rise in pressure inside the intake manifold blows back through the PCV hose and slams the pintle shut.
This prevents the flame from traveling back through PCV valve and possibly igniting fuel vapors inside the crankcase. Because the PCV system is relatively simple and requires minimal maintenance, it is often overlooked. The common replacement interval for many PCV valves is 50, miles, yet many engines have never had the PCV valve replaced. Many late model owners' manuals do not even have a recommended replacement interval listed for the PCV valve. The manual may only suggest "inspecting" the system periodically.
PCV valves can last a long time, but they may eventually wear out or clog -- especially if the vehicle owner neglects regular oil changes, and sludge builds up in the crankcase. The same sludge and oil varnish that gums up the engine can also plug up the PCV valve.
A restricted or plugged PCV valve cannot pull moisture and blowby vapors out of the crankcase. This can cause engine-damaging sludge to form, and a backup of pressure that may force oil to leak past gaskets and seals.
The same thing can happen if the pintle inside the PCV valve sticks shut.
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