Many owners Nissan Almera Classic Over time, they encounter a characteristic metallic knock in the engine, which is often confused with a malfunction of the hydraulic compensators. However, on units of the series K4M and K7MThere are no hydraulic compensators installed on this model, and adjustment is carried out mechanically. Ignoring this procedure leads to accelerated wear of the camshaft cams and burnout of the valve seat, which entails costly repairs to the cylinder head.
Timely adjustment of the thermal gap is not just a way to eliminate noise, but a critical operation for maintaining compression and stable engine operation. If you hear a knocking noise that increases with increasing speed, you need to immediately check the condition of the gas distribution mechanism. Neglecting this simple maintenance measure can turn a reliable power unit into a source of serious problems after just a few tens of thousands of kilometers.
Features of the timing belt design and why adjustment is needed
At the heart of the engine Almera Classic lies a time-tested design where the clearance between the camshaft cam and the valve tappet is set manually. Over time, the metal heats up and cools down, changing its physical dimensions, and with prolonged use, natural wear and tear occurs on the rubbing surfaces. This leads to the gap increasing or decreasing, disrupting the valve timing.
When the gap is too large, the valve does not have time to fully open, which reduces engine power and causes a characteristic knocking noise. If the gap is too small, the valve does not close tightly when heated, causing gases to break into the combustion chamber, causing the valve disc to burn out. For owners Nissan It is important to understand that these motors do not have automatic adjustment, so human intervention is inevitable when a certain resource is reached.
- 🔧 Wear of pushers - the main reason for changes in clearances after 100,000 km.
- 🌡️ Thermal expansion - metals expand when heated, and without clearance the valve will not close tightly.
- ⚙️ No hydraulics — the K4M design does not provide automatic compensators, only shims.
Preparation of the workplace and necessary tools
Before starting work, you will need to prepare a garage or overpass with sufficient lighting, as access to the cylinder head may be limited. Remove the decorative plastic cover of the engine and disconnect the negative terminal of the battery to eliminate the risk of a short circuit when removing the sensors. Make sure that the engine has completely cooled down to room temperature, since all measurements are carried out strictly on a cold engine.
To perform the operation, you will need a set of wrenches, feeler gauges for measuring gaps and special tools for compressing the pushers. Without a specialized tool, adjusting the washers is almost impossible, since the valve spring has significant force. Attempting to push the tappets out with a screwdriver may result in mechanism failure or damage to the camshaft surface.
- 📏 Flat probes - set from 0.10 to 0.50 mm in 0.05 mm increments for accurate measurements.
- 🔑 Keys and sockets — a set of 8, 10, 12, 13, 17 and 24 mm for removing the timing cover.
- 🛠️ Special tools - a mandrel for compressing the pusher (or a powerful clamp with an adapter) and tweezers for removing washers.
☑️ Preparation for valve adjustment
Step-by-step procedure for removing the timing cover and accessing the mechanism
Start by removing the plastic casing covering the top of the engine and removing the cylinder head cover bolts. Be extremely careful with the cover gasket, as damage to it will lead to oil leaks in the future. If the gasket is stuck, carefully pry it off with a flathead screwdriver, being careful not to scratch the adjacent aluminum surfaces.
Once the cover is removed you will have direct access to the camshafts and valve arms. Inspect the condition of the camshaft seals and, if necessary, replace them immediately to avoid subsequent oil leakage. Clean the surface from dirt and carbon deposits so that debris does not get inside the mechanism during further manipulations.
Before removing the timing cover, take a photo of the location of the bolts and their length, as they may differ in size and it is easy to mix them up during assembly.
Technology for measuring and adjusting the thermal gap
The adjustment process requires consistency: first, set the piston of the first cylinder to the top dead center (TDC) of the compression stroke. To do this, rotate the crankshaft by the pulley bolt clockwise until the mark on the pulley coincides with the mark on the cover, and the camshaft cams above the first cylinder are directed upward (away from the levers).
The gap is measured using a feeler gauge between the camshaft cam and the valve tappet. For intake valves, the standard clearance is 0.15-0.25 mm, for exhaust valves - 0.25-0.35 mm. If the dipstick passes too freely or does not enter at all, the gap requires adjustment. Remember that the accuracy of the measurement affects the performance of the motor in the future.
- 📉 Intake valves — the gap should be within 0.15–0.25 mm on a cold engine.
- 📈 Exhaust valves — the gap should be within 0.25–0.35 mm on a cold engine.
- 🔄 Check procedure — check the valves sequentially, turning the crankshaft half a turn (180 degrees) for each subsequent cylinder.
⚠️ Attention: Never take measurements on a hot engine! Thermal expansion of the metal will distort the readings, and you risk setting the wrong clearances, which will lead to burnt valves.
If the gap is not within the standard, it is necessary to remove the adjusting washer. To do this, press the pusher with a special tool all the way so that the spring is compressed, and carefully remove the washer with tweezers. Pay attention to the markings of the washer - it may be knocked out at the end or require measuring the thickness with a micrometer.
- Each maintenance according to the regulations
- Once every 2 years
- Only when something breaks
- I don't know when to
Calculation and selection of new adjusting washers
Selecting a new washer is based on a simple formula that must be applied to each valve. If the current gap is larger than normal, you need a thicker washer; if less, thinner. The calculation formula looks like this: $A = B + (C - D)$, where $A$ is the thickness of the new washer, $B$ is the thickness of the old one, $C$ is the measured gap, $D$ is the desired gap.
For convenience, many mechanics use ready-made correspondence tables, where the thickness of the washers is indicated in increments of 0.05 mm. Standard range of washer thickness on motors K4M varies from 2.50 mm to 3.75 mm. It is important to select a washer with the closest possible value, since a deviation of even 0.05 mm can be noticeable when the engine is running.
| Parameter | Inlet valve(mm) | Exhaust valve (mm) | Deviation tolerance |
|---|---|---|---|
| Minimum clearance | 0,15 | 0,25 | ± 0,02 |
| Maximum clearance | 0,25 | 0,35 | ± 0,02 |
| Recommended average | 0,20 | 0,30 | - |
| Washer thickness pitch | 0.05 mm | ||
Where can I find the markings on the washers?
The thickness marking may be stamped on the outside of the washer, but is often erased. In this case, the only way to find out the thickness is to use a micrometer and measure the washer yourself.
Installation of washers and final assembly check
After selecting the washers, carefully install them into the pusher seats, making sure that they lie flat and are not distorted. Slowly release the pushrod compression tool until the spring returns to its original position and check the clearance again with a feeler gauge. The probe should enter with a little effort, but not with difficulty, and not dangle loosely.
Reassemble the engine in reverse order, not forgetting to replace the timing cover gasket. Apply sealant to the corners of the cover, if specified in the instructions, and tighten the bolts crosswise to the recommended torque. Start the engine and listen to the operation - the knocking should disappear, and the engine should run smoothly at all speeds.
A correctly set gap guarantees no knocking, stable compression and no burnout of valves during long-term operation.
⚠️ Attention: If the knocking does not disappear after adjustment, check the condition of the rockers (rocker arms) and camshaft. Wear on the cams or the levers themselves cannot be corrected by replacing the washers.
Frequent mistakes when self-adjusting
One of the most common mistakes is ignoring the engine temperature. Many beginners try to adjust the gaps immediately after a ride, not realizing that the metal is still expanded. This leads to the fact that when cooling, the gaps become too small, and the valves begin to “sour” or burn out.
Another mistake is incorrect TDC setting. If the piston is not at the exact top position of the compression stroke, you will adjust the wrong valves, which will lead to chaos in the timing. Always check the marks on the pulley and cover, as well as the position of the cams.
- ❌ Ignoring labels — adjustment “by eye” without checking the position of the crankshaft.
- ❌ Hot work — measuring gaps at temperatures above 30-40°C.
- ❌ Damage to washers - scratches or deformation during removal and installation.
FAQ: Answers to frequently asked questions from owners
How often should the valves on the Almera Classic be adjusted?
Engine regulations K4M provides for checking clearances every 60,000 km. However, if a characteristic knocking sound appears, the check should be carried out unscheduled, without waiting for the scheduled time.
Is it possible to adjust the valves without removing the camshafts?
Yes, on engines K4M and K7M adjustment is made without removing the camshafts. Simply remove the cylinder head cover and use a special tool to compress the tappets.
What happens if the exhaust valve clearance is too small?
If the clearance is small, the valve will not close completely when the engine heats up. Hot gases will rush out, causing the valve plate and seat to burn out, resulting in loss of compression and the need for a major overhaul of the cylinder head.
Do I need to change the timing cover gasket with every adjustment?
It is highly recommended to change the timing cover gasket every time it is removed. An old gasket may lose elasticity and fail to seal, resulting in oil leaks that are difficult to fix without disassembly.
Is it difficult to find shims for Nissan Almera Classic?
Washers are a standard consumable item and are sold at most large auto stores or to order. They have standard sizes in increments of 0.05 mm, so choosing the right size is easy.
Adjusting the valves Nissan Almera Classic - This is a task that requires patience and accuracy, but is quite feasible to complete independently if you have basic skills and tools. Correctly performed tuning will extend the life of the engine and ensure its quiet and economical operation for many years. Do not delay a visit to service or independent work at the first sign of knocking, as the cost of inaction may be significantly higher than the cost of adjusting washers.