The PCV valve
When an engine is running, the exhaust gases blow through the piston rings to the crankcase, this process also occurs to a lesser extent during compression. In earlier times, these hydrocarbon-laden gases carrying oil droplets from the crankcase could escape into the atmosphere and, as a result, these engines were always leaking oil. It was very normal at that time, even the estoperas and together were made to contain large boats, not much effort was made to make hermetic fair, far from it.
This process took the form of a problem from the 1950s, when it was found that these gases caused pollution and increased smoke in the cities. In this way, and, motivated to an invention of the GM to ventilate the tanks of war, where the exhaust gases were recirculated to the intake manifold that casually reduced the emissions of these machines, already for the decade of the 1960s it was implemented compulsory in automobiles and in this way harmful hydrocarbons do not escape into the atmosphere.
Then the PCV valve (PCV: Positive Crankcase Ventilation Valve) allows the passage of oil and hydrocarbon vapors generated in the crankcase to the intake manifold and then to the combustion chambers where they are burned, thus eliminating the high pressure generated in the crankcase. In turn, this valve must close at the time of a deceleration of the engine, since the overpressure produced in the intake manifold would go to the crankcase generating the same problems.
In general, the PCV is closed by the spring when the engine is off or if an intake deflagration occurs. It closes for in a first case to avoid the entry of atmospheric air to the crankcase rich in steam water that, if it liquefies inside the engine, produces mud and other undesirable things, and for the second case avoid the entrance of overpressure or even flame the oil ... with the dangers that this implies.
When the machine is turned on at idle speed or minimum RPM, the PCV is semi-open due to the high vacuum that occurs at the engine intake. This is done because the mixtures usually do not contain a lot of air and it would not be a good idea to try adding oil, gasoline and little air to ignite it. It would not burn out completely.
When we accelerate the engine, the vacuum of the intake manifold decreases due to the entry of more air. This makes our PCV in working position and in this way as more air is entering the intake, we can put more oil, which we can burn without problems in combustion.
In the previous image you can see the animation of how this process is.
As you can see, the valve only lets flow in one direction (out of the crankcase). That is why they usually bring a little arrow, which indicates the direction of the flow so that it is installed correctly
Where are they?
It is usually connected to the intake air inlet by a hose about 2 centimeters in diameter. Not necessarily the side of the intake manifold is by hose. Below I show you an image of what a PCV valve looks like and its mounting types.
If the PCV valve becomes clogged or very clogged, A LOT OF PRESSURE is generated IN THE CRANKCASE that bursts the crankcase seals, the cylinder head cover, causing oil leakage, even loss of engine performance.
When it is open, the faults are accumulation of oil in the intake hoses, spark plugs dirty by traces of oil and in some cases very severe (when the engine passes oil) can dirty the air filter of the engine with traces of oil.
If oil leakage problems are noticed by seals and engine seals
Or if when removing the oil dipstick, too much vapor is visible.
Or if we have spark plugs that after a few days of having cleaned them, they get dirty and there are no symptoms of compression loss (the engine is running oil).
The most likely thing is that our PCV needs maintenance.
Test the PCV valve
Checking it is pretty simple.
- Remove the valve.
- Blow against the direction of the arrow. There should be no flow.
- Blow in the direction of the arrow. There should be flow.
If it is very dirty, it is advisable to clean it with some solvent that does not damage the internal gums.
And well, that's all for the moment.
I hope you like it,
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