Car pcv valve

How to detect the crankcase ventilation system failure

You can check the crankcase ventilation system serviceability using a pressure gauge. For this, it is necessary to connect the gage to the oil filler neck by means of a special adapter. Warm up the engine before starting measurements. At a speed of 700-800 revs per minute, the pressure should be 500-1500 Pa. When the engine speed increases to 2200-3500 rpm, in the crankcase there should be created a vacuum within the range of 100 to 500 Pa. If the pressure does not drop with the increase of revolutions, then the crankcase ventilation system bypass valve has failed. If the vacuum exceeds the normal value, most probably the air filter is clogged.

NB! These values are generalized. They are relevant for engines with the displacement of 1.8-3 liters. See what pressure of crankcase gas should be in your vehicle in the car technical manual.

If you do not have a manometer, put your hand over the filler neck and ask your assistant to raise the engine speed to 2000-2500 revs per minute. If you feel an increase in pressure at the same time, the crankcase ventilation system is defective.

To assess the bypass valve state, dismantle it and blow out first from one, then from the other side. A properly functioning component allows air to flow in only one direction.

You may identify that the crankcase ventilation system has to be checked by the following signs:

• oil in the throttle unit;
• unstable engine operation at idle;
• change in color and smell of exhaust gas;
• increased oil consumption;
• hindered engine start;
• deterioration of the vehicle dynamic performance;
• loss of engine power;
• abnormal sounds in the intake manifold area.

Causes of the crankcase ventilation system failure

It is advised to flush the crankcase ventilation system each time when doing the routine oil replacement. Otherwise, the accumulated dirt can block narrow ventilation ducts, hoses and connecting pipes. This results not only in the system performance faults, but also in the accelerated wear of its components.

Usage of low-quality oil is dangerous for the crankcase ventilation system. Aggressive components included in its composition can disrupt rubber seals, while low cleaning ability leads to the accelerated deposit formation on the internal surface of ducts and hoses, jamming of the valve or rupture of its membrane. The use of vehicle with incorrectly working or insufficiently lubricated engine results in similar effects.

In some cases a fault of the system occurs due to water ingress into it, or water condensate formation. At low temperatures, water freezes blocking the ventilation ducts and holes. To eliminate this problem, crankcase heating is provided in the design of many vehicles. But if it is faulty, and the car is used in a region with a humid and cold climate, the risk of freezing considerably increases.

Repair and replacement of the crankcase ventilation system

Often the crankcase ventilation system performance can be restored by cleaning it from contaminants. For this you need:

1. Dismantle the engine cover.
2. Disconnect the hose of the large ventilation branch from the throttle fitting, having squeezed and slided aside the clamp.
3. In a similar way, disconnect the hose of the small ventilation branch - first from the connector fitting, then from the back pressure valve fitting.
4. Loosen the back-pressure valve and unscrew it from its location hole in the cylinder head cover.
5. Disconnect the hose of the large ventilation branch from the cylinder head fitting, having squeezed and slided aside the clamp.
6. Flush the removed hoses and the valve with gasoline or kerosene, then dry them with compressed air.
7. Clean the holes of the fittings from the accumulated deposits.
8. Reinstall the parts performing the procedure in the reverse order.

Cracked or hardened hoses, deformed or damaged clamps require replacement. A faulty PCV valve (positive crankcase ventilation valve) can be restored by installing a new membrane. But if the housing or the threaded connection of the part is damaged, you will have to buy a new part, or, in some cases, a valve cover assembly.

Often, it is easy to replace the oil separator filter element on your own. For this, you have to remove the unit cover, after releasing the clips; and then to remove the faulty component and install a new one in its place. You can repair the oil separator valve if there is a need.