Positive Crankcase Ventilation (PCV) systems allow filtered fresh air into the engine to remove water vapor, blow-by gases and other contaminants from the engine crankcase. Over time, the PCV system components can become clogged or damaged, impacting the performance of the PCV system. Common symptoms of a faulty PCV system include rough idling, engine hesitation, and increased oil consumption.
To properly maintain the PCV system on a Volvo 940, it is essential to understand its components and how they function. Here is a detailed explanation:
1. PCV Valve: The heart of the PCV system is the PCV valve, which regulates the flow of air from the crankcase to the intake manifold. It opens when the engine vacuum is high and closes when the vacuum drops, preventing the excessive entry of air into the engine. As the PCV valve can get clogged or stick over time, it should be inspected and replaced as needed.
2. Crankcase Vent Hose: This flexible hose connects the PCV valve to the air cleaner assembly and allows for the movement of air between the crankcase and the engine's intake system. Over time, this hose can become cracked, brittle, or clogged, impairing the PCV system's functionality, If the hose shows any signs of damage or deterioration, it should be replaced.
3. Inlet Tube: The inlet tube is a small hose that connects the PCV valve to the intake manifold. It ensures that filtered fresh air is drawn into the engine crankcase to mix with and dilute the crankcase vapors. Inspect the inlet tube for cracks or blockages, and replace it if necessary.
4. Flame Trap: The flame trap, a mesh-like component located between the PCV valve and the intake hose, acts as a barrier to catch oil particles and prevent them from being drawn into the intake manifold. Over time, the flame trap can also become clogged, which affects the air and vapor flow within the PCV system. Replacing the flame trap according to the manufacturer's recommendations is essential.
5. Manifold Cover Gasket: The manifold cover gasket, located where the PCV valve meets the intake manifold, ensures a proper seal and prevents any vacuum leaks that could impact the PCV system's efficiency. If the gasket is damaged, it can cause air leaks and lead to rough idling and other performance issues. Inspect and replace the manifold cover gasket as needed to maintain a sealed system.
6. Breather Cap: Situated on the valve cover, the breather cap serves as a one-way valve, allowing air to escape from the engine crankcase but preventing unfiltered air from entering. A faulty or damaged breather cap can lead to increased crankcase pressure and compromise the PCV system's effectiveness. Replace the breather cap if it is damaged or shows any signs of deterioration.
Regularly inspecting and maintaining these PCV system components will ensure optimal engine performance, reduce emissions, and prevent premature wear of engine parts. It is advisable to refer to the Volvo 940 service manual for specific maintenance intervals and detailed instructions.
