Where is the PCV valve? Characteristics and operating principle

PCV - forced crankcase ventilation system. The functioning of the power unit of the car largely depends on its condition.

What is the PCV system for?

The main task of this system is the withdrawal of crankcase gases from the engine. They are available in all power units, regardless of their novelty and service life. The only difference between them is composition and quantity. Crankcase gases are formed in the engine when the fuel-air mixture is compressed in the cylinders and during the working stroke, when the pistons go down and the mixture is already set on fire. Under high pressure, they get into the crankcase of the engine and often into the valve caps in small volumes.

In the crankcase, they interact with the engine oil, starting to oxidize it. The pressure in the crankcase increases, as gases continue to flow into it. Because of this, you can throw out oil seals, a dipstick or squeeze out the lid of the oil filler neck. Simply put, under increased pressure, gases are trying to leave the crankcase and are looking for the weakest point for this. The PCV system exists to remove crankcase formations, it monitors the pressure in the system. From the valve covers, the gases are removed by means of ventilation. To date, there are four main types of such systems.

Open system

A distinctive feature of this type of system is the connection with the atmosphere. The gases accumulated in the crankcase under their own pressure are discharged through the vent valve. In terms of ecology, this is not the best option, because they contain a large number of harmful substances. In this case, the release of gases is accompanied by an unpleasant smell and high temperature nearby the car.

Fresh air supply system

The design of this system is similar to the previous one. But thus it has an air inflow. Passing through the filter element, it flows through a separate branch pipe into the crankcase, and from there it is discharged through the control valve into the atmosphere together with the gases. This system is extremely rare. It has a large number of disadvantages, so it was practically not used in cars.

Closed flow system

The air entering the crankcase exits along with the gases through a special valve into the space to the throttle valve. This system is rare. It has its pluses and minuses, because engine oil reacts with air.

Closed exhaust system

The most common system today. Gases accumulated in the crankcase are drawn out of it. The principle of the system is as follows: behind the throttle valve near the intake manifold there is a branch pipe in which there is a PCV valve and oil separator. When you press the accelerator pedal and open the damper in the intake manifold creates a vacuum, which leads to a tightening in it of air. Accordingly, back pressure is generated in the valve spout. This leads to its opening and drawing of crankcase gases into the inlet, entering the combustion chamber and re-burning. From the ecological point of view, this system is the best.

PCV System Construction

Depending on the engine, the structure of the PCV system can be different. For V-shaped and in-line motors, it differs in the arrangement of parts: on the first engines, for example, there are two covers. Often, the ventilation systems of the valve caps and crankcase are combined into one system. However, in general, the construction of such systems is the same. The main elements are as follows:

1. Branch pipes. Due to the vacuum formed in the intake manifold, gases are drawn through them. The strength of the nozzles should be high, because the substances being removed are characterized by high temperature and no less pressure. In most cases, such parts are either plastic or reinforced. Often you can find metal options.
2. The PCV valve. It regulates the process of discharge of crankcase gases and prevents the ingress of air. The PCV valve is blown only towards the collector. When purged toward the crankcase, it closes. However, you can find both bilateral and electric valves.
3. Oil separator. In the crankcase space there is always a specific fog, as the engine parts are constantly in motion. Accordingly, on them the oil is distributed. In some systems, there are internal nozzles that spray it. The oil separator is designed for separating crankcase gases and oil, outputting the first and leaving the second in the engine.

Where is the PCV valve located?

The location of the part may vary depending on the particular make and model of the car and the type of engine. In most cases, it is located on the engine valve cover.

PCV valve design features

The main task of the PCV valve in the ventilation system is to adjust the pressure of the crankcase gases by feeding them to the intake manifold. When the engine is braking and idling, the throttle flap is slightly ajar. But at the same time the volume of crankcase gases is low. Therefore, a small channel is sufficient for normal ventilation. Valve valve in this situation under the influence of high vacuum is drawn. But the channel for the supply of crankcase substances overlaps, releasing their small volume.

The number of formations in the crankcase increases dramatically when the gas pedal is pressed and at high loads on the engine. Accordingly, the PCV valve will occupy such a position to produce as much as possible volume. In such systems, there is usually a special flashback mode, which is characterized by the breakthrough of burning gases into the intake manifold from the cylinder. In this case, the PCV vent valve is under the influence of pressure, but not of vacuum, which leads to its complete closure. This allows you to prevent the possibility of igniting the fuel vapor accumulated in the crankcase.

Malfunction of the ventilation system of crankcase gases

Breakdowns of the PCV system can cause leakage of engine oil. The branch pipes of the ventilation system, clogging, create excessive pressure in the crankcase . This leads to the exhaust of the exhaust gases together with the oil from the engine. Initially, the oil can protrude through the orifice of the probe in place of the joints and seals. The most unpleasant consequence may be the squeezing of the oil seals. Termination of the proper operation of the oil separator of the ventilation system leads to the appearance of oil deposits on the air filter and throttle valve . If the PCV valve does not work correctly, this can lead to the creation of an enriched fuel mixture.

PCV Whistle

A thin, barely audible whistle of the engine is a problem that owners of foreign cars of different brands quite often face. For example, he often worries the owners of the car "Nissan". The PCV valve causes this fault. Whistling appears due to the design features and the work of the part itself. The PCV valve is enclosed in a plastic housing inside which is a ball or piston lifted from the inlet side of the airflow by a spring. In non-working position, he is in a closed position.

When the volume of crankcase gases increases, the air pressure is applied to the valve. This leads to its displacement and the release of airflow into the system. Over time, the spring and the housing walls are contaminated with small oil particles, which causes the valve to close tightly. When the accelerator pedal is depressed and the throttle valve is opened, a vacuum is created in the intake manifold, a large amount of air is drawn through the resulting clearance, which causes the engine to whistle.

Removing the whistle by cleaning the valve

Valve PCV "Lacetti" is low-cost, which saves money on the repair of this car. However, in order to get rid of the whistle of the engine, it is not necessary to resort to replacing the part. The cause of the appearance of third-party sound is the contamination of the valve. To eliminate such a malfunction, it is sufficient to clean the PCV valve "Ford", "Nissan" or another machine. The design of the part is very simple. However, it is worth to carefully consider the body, which on older models of cars was made of aluminum, and the new ones are mostly made of plastic.

Cleaning the PCV valve

You can clean the valve in several steps:

• Withdrawal. To clean the valve, it must be removed. It is located next to the air filter housing. The valve can be located on the cover, fixed to the ventilation pipes of the crankcase or stay elsewhere.
• Cleaning. Depending on the material from which the valve body is made, the cleaning method changes, and no mechanical effort is required. To clean the aluminum part, you can choose any cleaning agent: liquid or aerosol sprayed onto the surface or used as a cleaning bath. In the latter case, the valve is placed in a container filled with detergent. For the cleaning of plastic casings, aggressive compounds can not be used: they can damage the part, which can lead to its complete replacement.
• Installation. The cleaned part is returned to the place and fixed.

It is easy to clean the PCV valve: Ford Focus has you, Nissan or Audi - it does not matter. Despite this, it is desirable to entrust the process to the masters. Qualitative thorough cleaning will help to eliminate an unpleasant whistle.

When should I change the valve?

Many owners of imported cars are faced with the need to replace a consumable part, such as a PCV valve. "Chrysler" quite often requires such a procedure. Symptoms of the fact that it is time to stock up a new valve are the following factors:

• The appearance of a thin whistle under the hood of the car.
• Floating idle.
• Increase the amount of oil in the intercooler. It is in it and with a working PCV valve, but not in such large volumes.
• Increase in oil consumption.
• Reduction of boost pressure. In this case, the car behaves differently than before.
• From the candle wells, oil filler or feeler, oil appears. As a result, it can lead to leakage of the crankshaft oil seals. Elimination of such trouble will result in a large penny.
• From the exhaust pipe at idle rushing out clouds of dark gray smoke.

Replacing the PCV valve

After acquiring the necessary parts, you can begin the process of replacing the valve. In this case it is necessary to remember about such nuances:

1. To replace or clean the PCV valve, the intake manifold must be removed. The procedure is simple and fast, it is enough to have the necessary tool at hand.
2. A valve is placed on top of the cylinder block, between their heads. Access to it is small, but it is quite enough to replace it.
3. The lower part of the collector can not be removed completely, just raise a little.
4. To the valve PCV from under the "brains" of the car goes the tube. It must be disconnected from the second part and remove both halves. As a result, only the valve will remain in the oil separator.
5. The space around it is desirable to clean. It is best done by the flow of air.
6. The valve is turned anti-clockwise. It usually has a square ledge that facilitates the removal process. This can be done with platypuses - not very convenient, but quickly.
7. The unscrewed PCV valve must be inspected and flushed. This can be done with a clean thin hose. The part must be blown in the direction of the collector.
8. A good valve is better to change after 100 thousand kilometers of run.
9. Install the new valve and assemble everything in reverse order.

At the same time, you can check the integrity and replace the branch pipes as necessary. Their main faults are:

• From time to time, their upper part is flattened and starts to pump air;
• The connections between the hoses start to siphon off.

Fix it fairly simply - either by replacing the nozzles, or by spreading seams and joints with a sealant. The valve replacement process is described in detail in the vehicle manual. The instruction is illustrated by the necessary photos.

The PCV valve is one of the parts of the crankcase ventilation system, on which the functioning of the motor of the car depends. Its malfunctions can lead to an increase in the consumption of engine oil, a deterioration in handling and the failure of the power unit. To prevent such consequences, the timely cleaning and replacement of the PCV valve will help. Such procedures are carried out quickly and simply. They do not require large expenses and can be carried out independently, without the involvement of car service masters. The car's engine performance depends only on its owner.