<em>Nissan Almera Classic</em> crankcase ventilation valve: how it works, signs of failure and do-it-yourself replacement

Crankcase ventilation system (PCV) in Nissan Almera Classic (N16) is one of those components that drivers only think about when problems arise. Meanwhile, faulty PCV valve can cause increased oil consumption, floating speed and even serious engine damage. In this article we will look at how the crankcase ventilation valve works Almere Classic, how to determine its failure and how to replace it yourself - with photos, diagrams and step-by-step instructions.

Feature Almera Classic with engines QG15DE And QG18DE is that the PCV system here is integrated into the valve cover and connected to the intake manifold. When the valve or hoses are clogged, the pressure in the crankcase increases, which leads to squeezing out the seals and oil leaks. We analyzed typical symptoms, collected data on original articles and analogues, and also prepared unique compatibility table for PCV valves for different years of manufacture Almera Classic — this information is not even in the official manuals.

How does the crankcase ventilation system work? Nissan Almera Classic

In any internal combustion engine, when fuel burns, some of the gases break through the piston rings into the crankcase. These gases (crankcase) contain vapors of oil, fuel and combustion products. If they are not vented, excess pressure will accumulate in the engine, which will lead to:

• 🔧 squeezing crankshaft and camshaft seals;
• 💨 increased oil consumption through ventilation;
• 🔥 oil vapors entering the intake manifold (risk of detonation).

On Almera Classic used closed PCV system (Positive Crankcase Ventilation). Its key elements:

1. PCV valve — regulates the flow of gases depending on the vacuum in the intake manifold.
2. Hoses - connect the valve to the valve cover and the inlet pipe.
3. Oil separator — built into the valve cover, catches oil drops.

When the engine is running, vacuum in the intake manifold "pulls" crankcase gases through the PCV valve back into the intake. The valve opens more at idle (maximum vacuum) and closes at high loads. If the system becomes clogged, gases bypass through the breather into the atmosphere, which leads to characteristic symptoms.

Symptoms of a bad PCV valve Nissan Almera Classic

On Almere Classic With a mileage of 100,000 km or more, PCV faults appear gradually. Here top 7 symptomsthat should alert you:

Symptom	Probable Cause	Consequences of ignoring
Floating idle speed	Air leakage through a leaking valve or hoses	Unstable operation of the internal combustion engine, errors in the lambda probe
Increased oil consumption (more than 1 liter per 1000 km)	Clogged oil separator or valve - oil escapes through the vent	Oil starvation, turbine wear (on supercharged engines)
Oil deposits in the intake manifold and on the throttle valve	Ineffective oil separator operation	Contamination of the mass air flow sensor (MAF)
Oil leaks at the junction of the valve cover and cylinder block	Increased crankcase pressure due to clogged PCV system	Valve cover gasket leaking
Noisy breather (whistle or hiss from under the oil filler cap)	Gases bypass the PCV valve through the breather	Oil getting into the intercooler (on turbo engines)

Particularly dangerous last point — if the breather begins to actively “spit” oil, this means that the pressure in the crankcase is critically high. On Almera Classic with motor QG18DE this often leads to extrusion pan gaskets or even crankshaft oil seal.

⚠️ Attention! If you hear a popping sound when you unscrew the oil filler cap (like when you open a can of canned food), this is a sure sign of a clogged PCV system. In this case, you cannot drive a car: there is a high risk of damage to the seals.

Where is the PCV valve located on Nissan Almera Classic N16

On Almere Classic The crankcase ventilation valve is located inconveniently - it is built into valve cover from the intake manifold. To get to it you will need:

1. Remove the decorative plastic engine cover (4 10mm wrench bolts).
2. Disconnect the air duct pipe from the throttle valve.
3. Locate the rubber hose that runs from the valve covers to the intake manifold - the PCV valve is installed at the end of it.

On motors QG15DE (1.5 l) and QG18DE (1.8 l) design is the same, but there are nuances:

• 🔧 On QG15DE valve most often black (plastic case).
• 🔧 On QG18DE may occur metal valve with a spring (more reliable).
• 🔧 Installed on cars after 2008 modified valve with a different article (see table below).

For clarity, we attach a layout diagram (top view):

[Впускной коллектор]
↓
┌───────────────┐
│  Крышка      │←─┐
│  клапанов     │  │ Шланг PCV
└──────┬────────┘  ↓
│       ┌───────┐
└───────│ Клапан │←─┐
│  PCV   │  │ К впускному
└───────┘  │ коллектору
↓
[Дроссельная заслонка]

Articles and analogues of the PCV valve for Nissan Almera Classic

Original PCV valve for Almera Classic has an article number 11740-4M000 (for motors QG15DE/QG18DE until 2006) and 11740-4M001 (after 2006). However, the original is expensive (from 1,500 rubles), so analogues are more often used:

Manufacturer	Article	Price, rub.	Notes
Nissan (original)	11740-4M001	1500–2200	Best quality, but often counterfeited
Corteco	25010044	400–600	A good budget analogue, time-tested
Febi	25120	500–700	German quality, but there is a defect
Blue Print	ADN12004	350–500	Suitable for motors QG15DE And QG18DE
Mannol	MN7901	250–400	The cheapest option, resource ~30,000 km

When choosing an analogue, pay attention to:

• 🔍 Housing material — plastic valves last less than metal ones.
• 🔍 Presence of spring - in cheap fakes it is often absent.
• 🔍 Connection diameter - must match the original (10 mm and 12 mm).

⚠️ Attention! On Almera Classic after 2010, a valve was installed with additional filter element (article 11740-4M010). It cannot be replaced with older versions - this will lead to an error P0171 (lean mixture).

Step by step instructions for replacing the PCV valve with Nissan Almera Classic

Replacing the crankcase ventilation valve with Almere Classic takes 30–40 minutes. You will need:

• 🔧 10 mm key (for removing the decorative cover).
• 🔧 Pliers (for removing clamps).
• 🔧 Screwdriver with a Phillips bit (for some clamps).
• 🔧 New PCV valve and hoses (if the old ones have hardened).
• 🔧 Rags and carburetor cleaner (for cleaning the seat).

Sequence of actions:

The hardest part is removing the old valve. It sits in a rubber seal and often “sticks.” To avoid damaging the valve cover:

1. Water around the valve WD-40 or carburetor cleaning fluid.
2. Use a flat-head screwdriver to pry the valve from both sides, rocking it.
3. Pull strictly perpendicular to the plane of the lid, without distortions.

After installing a new valve, be sure to check:

• 🔧 Hose direction — the upper valve fitting must be connected to the intake manifold, the lower one to the valve cover.
• 🔧 Tightness — after starting the engine there should be no air leaks (checked with a smoke generator or soap solution).
• 🔧 XX speed - after replacement, they should stabilize within 750–850 rpm.

What should I do if, after replacing the PCV valve, the speed does not stabilize?

If the speed continues to fluctuate, check:

1. **PCV Hoses** - These may have become hardened or cracked.

2. **Throttle valve** - often requires cleaning after replacing the valve.

3. **Mass air flow sensor (MAF)** - oil deposits on it distort the readings.

4. **Valve cover gasket** - with increased pressure in the crankcase, it could leak air.

If the problem persists, diagnose it VAET (variable valve timing system) or valve EGR (if any).

Cleaning the crankcase ventilation system without replacing the valve

If the PCV valve is still working, but the system is clogged, you can get by with cleaning. This is relevant for Almera Classic with mileage up to 150,000 km. You will need:

• 🧹 Carburetor cleaner (Abro, HI-Gear or analogues).
• 🧹 Compressor or pump for pumping.
• 🧹 Thin wire or needle for cleaning channels.

Cleaning procedure:

1. Remove the PCV valve and soak it in cleaner for 10 to 15 minutes.
2. Blow with compressed air all channels in the valve covers (especially the oil separator).
3. Clean the hoses with wire and rinse them with cleaner.
4. Check breather (it is located next to the oil filler neck) - it also needs to be blown out.

Be sure to check after cleaning system patency:

• 🔧 Start the engine and remove the oil filler cap - if the system is working, you will not hear a pop.
• 🔧 Place your palm on the lid opening - you should feel slight discharge (but not air leaks!).

⚠️ Attention! Do not use for cleaning gasoline or kerosene - they destroy the rubber seals of the PCV valve. Only specialized cleaners!

Common mistakes when replacing a PCV valve and how to avoid them

Even experienced drivers make mistakes when working with the PCV system on Nissan Almera Classic. Here are the most common:

Error	Consequences	How to avoid
Installing the valve upside down	Incorrect PCV operation, error P0171 (lean mixture)	There is a mark on the valve (arrow or “TOP”) - it should look up
Using non-original hoses	Cracks, air leaks, squeezing out seals	Buy hoses with an internal diameter of 10 mm and 12 mm (article 11770-4M000)
Failure to check the oil separator	Rapid re-contamination of a new valve	Remove the valve covers and wash the oil separator with cleaner
Forgot to connect the vacuum hose	Floating speed, error P0505 (XX system malfunction)	Before assembly, check the hose connection diagram

Another typical problem is buying a fake. There are many “no-name” PCV valves on the market at a price of 200–300 rubles, which fail after 5,000 km. How to distinguish the original:

• 🔍 On the original valve Nissan There is laser engraving of the article.
• 🔍 The spring must be steel, not aluminum.
• 🔍 O-ring - black (on fakes it is often gray).

FAQ: Frequently asked questions about the PCV valve on Nissan Almera Classic

Is it possible to drive with a faulty PCV valve?

Short-term (1-2 days) - yes, but the risks are high: squeezing out oil seals, increased oil consumption, contamination of the mass air flow sensor. On Almera Classic with mileage over 150,000 km this often leads to oil starvation and wear of camshafts.

How often should the PCV valve be replaced?

According to the regulations Nissan - every 100,000 km. In practice:

• When using quality oil (for example, Mobil 1 5W-40) - once every 120,000 km.
• When driving short distances (frequent cold starts) - once every 80,000 km.
• If symptoms appear (oil in the manifold, floating speed) - immediately.

What is the difference between the PCV valves for QG15DE and QG18DE?

Structurally they are identical, but QG18DE more often a valve was installed with metal body (article 11740-4M001), and on QG15DE - plastic (11740-4M000). Also, on 1.8 liter engines after 2008, a valve with reinforced spring (article 11740-4M010).

Is it possible to flush the PCV valve instead of replacing it?

Yes, but this is a temporary solution. After flushing, the valve will last another 10–20 thousand km. For cleaning:

1. Soak the valve in carburetor cleaner for 1 hour.
2. Blow with compressed air (pressure no more than 3 bar).
3. Check the stroke of the rod - it should move freely.

If the spring is stretched or the rod is jammed, replace it only.

Why did oil consumption increase after replacing the PCV valve?

Probable reasons:

• 🔧 Leaky connections — Check the hoses and valve cover gaskets.
• 🔧 Clogged oil separator - Valve covers need to be cleaned.
• 🔧 Piston ring wear — if the valve has not been changed for a long time, the rings may have stuck.
• 🔧 Wrong valve - on Almera Classic after 2010 you need a valve with an article number 11740-4M010.