Engine G15 by car Nissan Almera Classic is famous for its simplicity and reliability, but the gas distribution system requires regular attention. Unlike modern engines with hydraulic compensators, here we use a classic scheme with adjustment valve washers. Over time, the clearances change due to natural wear, which inevitably leads to a violation of the valve timing.
If you hear a characteristic metallic knock in the area cylinder heads or notice a loss of power during acceleration, this is a sure sign that the thermal clearances are outside the permissible limits. Ignoring this problem can lead to burnt valves and costly repairs. Adjustment valve washers - this is a procedure that you can perform yourself if you know the exact algorithm of actions and have the necessary measuring tools at hand.
Why adjustment is needed and how the system works
In design Nissan Almera Classic valves open through shims, which are installed between the camshaft cam and the valve stem. As the engine heats up, the metal expands and if the clearance is too small, the valve will not close completely, resulting in loss of compression. If the gap is too large, characteristic noise and impacts on the valve seats appear.
Process valve adjustment consists in selecting a washer of the required thickness to ensure ideal clearance when cold. For intake valves it is 0.15-0.25 mm, and for graduation - 0.25-0.35 mm. These numbers are critical: a deviation of even a hundredth of a millimeter can significantly affect the operation of the engine.
Necessary tools and preparation
Before you get started, make sure you have a complete set of tools. You will need gap gauge (a set with 0.05 mm increments is best), a micrometer for measuring the thickness of old washers and a set of socket heads. You cannot do without a special remover for the washers, since it is almost impossible to remove them with your fingers without the risk of damaging the parts.
The engine must be completely cool, preferably close to outside temperature. You cannot work on a hot motor, since the metal is in an expanded state, and the measurements will be incorrect. Remove the decorative plastic engine cover and valve coverby disconnecting all crankcase ventilation hoses and mountings.
- 🛠 Set of open-end and socket wrenches (sizes 8, 10, 12, 14, 17)
- 📏 Accurate micrometer (or high precision caliper)
- ⚙️ Special remover for shims
- 🔧 Torque wrench for tightening the lid
Step-by-step dismantling and measuring process
First, you need to set the piston of the first cylinder to the top dead center (TDC) of the compression stroke. To do this, rotate the crankshaft clockwise by the pulley bolt until the mark on the pulley aligns with the mark on the timing belt cover. Make sure that the camshaft lobes above the first cylinder are facing up and are not pressing on the washers.
Using gap gauge, measure the gap between the camshaft cam and the adjusting washer. Record the values obtained for all valves. If the gap is different from the norm, you will need to select a new washer. It is important to note that the old washers should not be thrown away immediately - they can be used as a standard for calibration.
To remove the washers, use puller. Push down on the valve tappet to release the washer and gently pry it up with tweezers or a magnet. Do not allow washers to fall inside the engine, as this can lead to catastrophic consequences for the cylinder-piston group.
⚠️ Attention: Be extremely careful when removing washers. Even small metal shavings that get into the oil passage or valve seat can cause serious engine damage.
Once removed, measure the thickness of each washer using a micrometer. Record your results in a table. Usually there are markings on the washers indicating the thickness in hundredths of a millimeter, but over time this can wear off or become unreadable, so mechanical measurement is necessary.
- Gap gauge
- Micrometer
- Calipers
- Laser gauge
The mathematics of selecting new washers
To choose the right new washers, you need to use a simple formula: N = V + (A - C), where N - thickness of the new washer, V - thickness of the old one, A is the measured gap, and C - desired gap. This formula allows you to accurately calculate which part needs to be installed.
For example, if the measured exhaust valve clearance is 0.45 mm, and the norm is 0.30 mm, then the gap is too large. This means the old washer is too thin. If its thickness was 2.50 mm, then there should be a new one 2.50 + (0.45 - 0.30) = 2.65 mm. Always round the result to the nearest standard washer size.
Manufacturers Nissan offer washers with a pitch of 0.05 mm, starting from 2.00 mm and ending 3.40 mm. If the calculated value falls between the standard sizes, choose a washer that gives a gap a little closer to the lower limit of the norm, since the metal will settle a little after the first hundred kilometers.
- 📐 Step of washers sizes:
0.05 mm - 🔢 Thickness range: from
2.00 mmup to3.40 mm - 🎯 Selection tolerance: ±
0.02 mm
Installation and final check
Install the new washers into place, making sure they sit straight and are not askew. The camshaft should be in a position where the cams do not press on the tappets. Carefully lower the shaft into place, being careful not to damage the washers. Tighten the camshaft bolts in several stages, starting from the center and working outward.
After installing all the washers and assembling the engine, it is necessary to repeat the procedure for measuring the gaps. Rotate the crankshaft, checking each cylinder. If the gaps are normal, you can install valve cover and gasket. Make sure that the gasket is not twisted and that it fits snugly against the surface.
☑️ Check before launch
Secure the cover using a torque wrench, observing the tightening torque. 10-12 Nm. Overtightening the bolts can lead to deformation of the cover and subsequent oil leaks. Don't forget to reconnect all the hoses and electrical connectors that you disconnected when you started.
Common mistakes when replacing
The most common mistake is installing washers on the wrong side or mixing them up. They also often forget to lubricate the camshaft before installation, which causes rapid wear of the cams in the first minutes of engine operation.
Cost and availability of spare parts
Shims are a consumable item that is sold individually. Cost of one original part Nissan varies depending on the store, but usually does not exceed several hundred rubles. However, if you need to replace 16 washers at once (for 4 valves in each of 4 cylinders), the amount can become significant.
Many owners Almera Classic They prefer to buy a set of washers, as it is more profitable. There are also similar parts from third party manufacturers such as JS Asakashi or Topran. They are often cheaper than the original, but the quality may be lower, so check the markings and thickness carefully before installing.
| Valve type | Gap norm (cold) | Typical washer thickness | Replacement frequency |
|---|---|---|---|
| Inlet | 0.15 - 0.25 mm |
2.25 - 2.80 mm |
Every 60-90 thousand km |
| Outlet | 0.25 - 0.35 mm |
2.50 - 3.10 mm |
Every 60-90 thousand km |
⚠️ Attention: Do not skimp on the valve cover gasket. Cheap analogues often harden after the first trip and begin to leak oil, which will lead to repeated disassembly of the engine.
Signs of Incorrect Adjustment
If after replacing the washers you still hear a knocking noise or feel that the engine is running rough, the calculation may have been done incorrectly. An excessively small gap causes valve burnout and loss of power, while too large a gap increases noise and reduces engine efficiency. Pay attention to the color of the exhaust gases and fuel consumption.
Sometimes the problem may not be with the washers themselves, but with wear on the camshaft or tappets. If the camshaft lobes show obvious signs of erosion or wear, simply replacing the washers will not solve the problem long-term. In such cases, a complete replacement of the camshaft is recommended.
- 🔊 Characteristic metallic knocking noise at idle speed
- 📉 Deterioration in vehicle acceleration dynamics
- ⛽ Increased fuel consumption for no apparent reason
Before purchasing new washers, be sure to check the wear on the camshaft lobes. If they are ground off, even perfectly matched washers will not ensure stable engine operation.
When finished, start the engine and let it idle. Listen to the sound of the valve mechanism. It should be smooth, without extraneous knocks. If everything is ok, test drive and check the engine oil level.
Adjusting valve clearances is not only about eliminating noise, but also guaranteeing proper combustion of the fuel mixture and long engine life.
FAQ: Frequently asked questions
Is it possible to adjust valves on a hot engine?
No, absolutely not. Metal expands when heated and the measurements will be incorrect. This will lead to incorrect selection of washers and subsequent problems with the engine.
How often do adjustments need to be made on the Nissan Almera Classic?
It is recommended to check clearances every 60,000 - 90,000 km. However, if a knock occurs, the check must be carried out immediately.
Do I need to change all the washers at once?
Not necessarily. If the clearances of only a few valves are outside the normal range, only those can be replaced. But to ensure uniform wear, the entire set is often replaced.
What to do if the required thickness of the washer is not on sale?
You can use the closest size washer, but the gap may be slightly different from ideal. As a last resort, you can order washers to order if they are not in stock.
⚠️ Attention: An incorrect calculation of the washer thickness by more than 0.1 mm can lead to burnout of the exhaust valve after only 2000 km.