Sedan owners Nissan Almera new generation (G15 body) are often faced with the issue of servicing the gas distribution mechanism. Engine HR16DE, installed on this car, is reliable, but requires periodic monitoring of the thermal clearances of the valves. Ignoring this procedure can lead to reduced power, increased fuel consumption and, in the worst case, burnt valves.
Many car owners mistakenly believe that hydraulic compensators make adjustment unnecessary, but the design HR16DE assumes the use of mechanical pusher cups. This means that clearances can change over time due to wear on the camshaft lobes or the cup itself. Timely intervention is the key to a long engine life.
Design features of the timing belt of the HR16DE engine
Engine HR16DE - This is a 16-valve unit with two camshafts. Unlike old designs, where adjustment was carried out with screws, here we use replaceable pusher glasses. This makes the process more labor-intensive, as it requires selecting the desired thickness of the glass, but it ensures high accuracy and no need for frequent adjustments.
The camshaft cams press on the cups, which transmit force to valve rocker arms. Over the course of the mileage, the metal wears out, and the gap between the cam and the glass decreases or increases. If the gap is too small, the valve will not close completely, resulting in loss of compression. If it is too large, a characteristic metallic knock appears, which intensifies when cold.
It is important to note that on Nissan Almera G15 There is no automatic gap compensation system. This requires the owner or craftsman to be careful when measuring. Errors in calculations may lead to the need to re-disassemble the cylinder head, which entails additional costs.
Diagnosis of the need for adjustment
You can determine that it is time to adjust the valves by indirect signs. The most obvious symptom is the appearance of extraneous noise at the top of the engine. The sound is reminiscent of the knocking of valves on old cars and is clearly audible when starting a cold engine, gradually fading as it warms up, if the gap is not critical.
Other signals may include: unstable engine operation at idle, misfires in individual cylinders and decreased acceleration dynamics. If you notice that your car has begun to consume more fuel, do not rush to change the oxygen sensors - check first valve thermal clearances.
The manufacturer recommends diagnosing gaps every 40,000 km, however, the actual situation may depend on operating conditions. Frequent short trips, driving in traffic jams or aggressive driving may shorten this interval. Regular inspection allows you to identify the problem at an early stage.
Tools and necessary materials
To perform the work you will need a set of specialized tools. Without it, it will not be possible to perform the procedure efficiently, since the measurement accuracy must be up to hundredths of a millimeter. The main tool is a set probes for measuring gaps, preferably with a thickness of 0.10 to 0.40 mm.
It is also necessary to have:
- 🔧 A set of socket heads and a ratchet for removing the cylinder head cover
- 🔧 Puller for pressing out pusher cups (or special tweezers)
- 🔧 Micrometer for measuring the thickness of glasses with an accuracy of 0.01 mm
- 🔧 New set of cylinder head cover and valve cover gaskets
Be sure to have clean rags and degreaser ready to remove old oil and dirt before assembly.
During your work you may need engine key (by 19 or 32 mm, depending on modification) to rotate the crankshaft. It is important to have a manual with a table of nominal clearances on hand so as not to make mistakes in the calculations. A mistake in choosing a glass can cost you the health of your engine.
Step-by-step adjustment instructions
Before starting work, the engine must be completely cooled, since measurements are carried out at ambient temperature. Remove the decorative engine cover, disconnect the sensor connectors and unscrew the valve cover bolts. Carefully remove the cap, being careful not to damage the gasket if you plan to reuse it (although it is better to replace it with a new one).
Next, 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, following the marks on the camshafts. On Almera G15 The marks must coincide with the plane of the cylinder head, and the cams of both shafts must be directed upward (in the shape of the letter “V”).
Measure the clearances on the intake and exhaust valves of the first cylinder using a feeler gauge. Then repeat the procedure for the remaining cylinders, turning the crankshaft 180 degrees (half a turn) for each additional cylinder. Write down all the obtained values in a table so as not to get confused when selecting new glasses.
The next stage is dismantling the glasses. Using a special puller or tweezers, carefully remove the pushers. Remember or label which cylinder and which valve each glass was removed from. This is critical for correctly calculating the thickness of the new element.
☑️ Preparation for adjustment
⚠️ Attention: Never try to pry off the glass with a screwdriver without protecting the cylinder head, as you can damage the seat, which will lead to an oil leak and the need to replace the entire cylinder head.
Removing camshafts
If the glasses are sitting very tightly, it is sometimes necessary to slightly rotate the camshaft to relieve pressure on the pushrod. However, on the HR16DE it is usually sufficient to use a special puller, since the valve springs have sufficient force.
After removing the glasses, measure their thickness using a micrometer. Compare the data obtained with the current gaps and calculate the required thickness of the new glass. The calculation formula is simple: new thickness = current thickness + (measured gap - nominal gap).
- Every 10,000 km
- Every 40,000 km
- Only when there is a knock
- I don't know the intervals
Correctly calculating cup thickness is a mathematically precise process where an error of 0.01mm can move the gap out of range.
Gap table and thickness calculation
For correct engine operation HR16DE Factory tolerances must be strictly observed. Intake and exhaust valves have different thermal expansion requirements, so their clearances are different. Below is a table with cold engine ratings.
| Valve type | Nominal clearance (mm) | Acceptable range | Note |
|---|---|---|---|
| Inlet | 0.15 - 0.25 | 0.10 - 0.30 | Depends on temperature |
| Outlet | 0.25 - 0.35 | 0.20 - 0.40 | Thermal expansion is higher |
| Glass thickness | 2.500 - 3.500 | In 0.025mm increments | Over 40 sizes available |
When calculating the thickness of a new glass, use the following logic: if the gap is larger than the nominal value, then the glass is too thin and you need to get a thicker one. If the gap is less than the nominal value, the glass is thick and a thinner one is needed. Always round up to the nearest standard commercially available glass size.
Order glasses with a small margin of size (for example, 0.05 mm larger and smaller than the calculated one), since during installation the gap may change slightly and correction may be required.
025 mm. This gives high tuning accuracy, but requires careful calculation. Do not try to “fit” the glass by grinding - this will disrupt the geometry and accelerate the wear of the camshaft.
Installation and final assembly
After selecting the new glasses, install them in their places, making sure that they go in all the way. Engine camshafts back, checking the alignment of the marks. Install new cylinder head cover gaskets, having previously degreased the surfaces. Apply sealant to the joints specified by the manufacturer, usually the corners of the lid.
The valve cover bolts are tightened in several passes with a certain tightening torque. Use a torque wrench to avoid cap distortion and oil leaks. The tightening torque is usually around 10 Nm, but always check the current specification for your year of manufacture.
After assembly, start the engine and let it idle for 5-10 minutes. Check for abnormal noise and oil leaks. If the knocking noise has disappeared and the motor runs smoothly, the procedure is completed successfully.
⚠️ Attention: If the knocking noise remains after adjustment, immediately stop the engine and check that the glasses are installed correctly. There may be an error in the calculation or debris getting under the glass.
A final hearing test and checking for oil leaks is a mandatory step to ensure there are no errors during assembly.
Common mistakes and tips
A common mistake made by beginners is to incorrectly determine TDC. On HR16DE There are two strokes when the piston is at its top point: the compression stroke and the exhaust stroke. The valves are only adjusted during the compression stroke when both valves are closed. If mixed up, you will adjust valves that should be open, with disastrous results.
Another problem is the use of low-quality or used glasses. The cups have microscopic signs of wear from the camshaft lobes. Installing old glasses may not give the desired result, since their working surface is already deformed. Always use new parts.
Do not ignore the condition of the camshafts during removal. Inspect the cams for scoring, chipping, or excessive wear. If the camshaft is worn, simply replacing the cups will not solve the problem and the noise will return very quickly. In such cases, the camshafts or cylinder head will need to be replaced.
FAQ: Answers to frequently asked questions
How often do valves on a Nissan Almera G15 need to be adjusted?
The recommended interval is 40,000 km, but if knocking or unstable engine operation occurs, a check should be carried out immediately. In difficult operating conditions (taxi, traffic jams), it is better to reduce the interval to 30,000 km.
Is it possible to adjust valves on a hot engine?
No, the procedure is strictly regulated for a cold engine (temperature about 20°C). On a hot engine, the metal expands and the measurements will be incorrect, which will lead to incorrect selection of glasses.
What happens if the valve clearance is too small?
If the gap is too small, the valve does not close completely when heated. This leads to burnout of the valve chamfer, loss of compression, unstable operation and failure of the catalyst due to unburnt fuel.
Is it difficult to find glasses of the right thickness?
Engine glasses HR16DE are a common spare part, but they have a large range of sizes (more than 40 options). Stores usually only have the most popular sizes in stock; the rest have to be ordered.
Is it possible to replace the glasses without removing the camshafts?
On the engine HR16DE this is practically impossible without the risk of damaging parts. A special tool allows you to remove the cup, but access to it and proper positioning usually requires loosening or removing the camshafts.
Valve adjustment is a routine but vital procedure for Nissan Almera G15. By performing it efficiently and using the right tools, you will ensure the engine has a long and trouble-free service. Remember that prevention is always cheaper and easier than major repairs.