Modern cars are becoming more sophisticated and smarter. This also applies to the gas distribution mechanism. It is very important that the valve always opens and closes at the right time, so that, ideally, there are no gaps between the camshaft and the valve itself. This has many benefits, such as increased power and reduced fuel consumption. Previously, the valves were manually adjusted, then mechanical "wide" pushers appeared (which, by the way, are still used on many cars), but the pinnacle of evolution was hydraulic compensators or simply "hydraulic compensators". They have many positive aspects, but there are also enough negative ones, in particular, they can knock. Today I will try to tell you in a simple and understandable language about the device, as well as about some breakdowns, there will be a video version at the end ...
First, the definition is:
Hydraulic compensators Are devices that use oil pressure to automatically adjust the clearances between valves and camshafts (or shaft). Thus, improving dynamic characteristics reducing fuel consumption. It is worth noting that the acoustic comfort also improves, the engine runs quieter.
BUT before the advent of hydraulic lifters, mechanical valve regulators were installed on cars ...
A bit of history
Hydraulic expansion joints have replaced less efficient mechanical valve controllers. As a rule, a conventional engine valve, say on a classic VAZ 2105 - 2107 engine, does not have a hydraulic compensator, so it often had to be adjusted, on average after 10,000 kilometers. The valve adjustment on, VAZ 2105 - 2107, was done manually, that is, you had to remove the valve cover and set the gaps using a special probe, which differed in thickness, which means you could choose for your run.
If the adjustment was not made, then the car engine began to make noise, the dynamic characteristics decreased, and the fuel consumption increased. After 40 - 50,000 kilometers, the valves generally had to be changed. That is, the mechanical adjustment of the valve, let's say "to put it mildly" - has outlived its usefulness, it was necessary to do something, so to speak, to improve the design.
So on front-wheel drive VAZ engines, they began to install mechanical pushers in front of the valve. If you exaggerate, then a large "hat" was simply put on the valve on top, it has a large diameter (than the old design), and therefore the wear is much reduced, because it is much more difficult to wear out a large diameter than a small one. But the adjustment still remained, of course not every 10,000 kilometers, much less often, but it is still recommended to do it. Usually this was done by placing repair "washers" of increased height. It is worth noting that “such” mechanical adjustments are quite effective and are still used by some manufacturers; adjustment with washers is recommended no earlier than 40-50,000 kilometers (if we talk about our VAZs) on some foreign cars, pushers run even longer. The big advantages are simplicity of design, unpretentiousness (you can cast semi-synthetic oils), as well as the relative cheapness of the structure. The downside is that when the "washers" were developed from above, the engine began to operate more noisily, the dynamic characteristics fell and the consumption increased. What was needed was a design that would automatically adjust the gap.
And now, to replace the mechanical adjustment of the valve, it came completely new technology... Everything is simple here - now you do not need to adjust the valves manually, the hydraulic lifters will do everything for you. They themselves will set the required engine valve clearance, which increases the engine resource, increases power, reduces fuel consumption, and the mechanism runs for quite a long time 120-150,000 kilometers (with proper maintenance). In general, a step forward.
What are the types of hydraulic lifters
These devices are widely used in timing systems. However, their counterparts are also used in chain tensioning, the so-called "tensioner timing chains". For this period of time, only 4 designs are used.
- Hydraulic pusher. Often used on modern cars to adjust the clearance between the valve and the camshaft
- Hydro support
- Hydraulic support for installation in levers and rocker arms. Mainly used on old timing mechanisms
- Roller hydraulic pusher
All 4 types have a place to be on different structures, although "hydraulic mounts" were often used earlier in engines. Now more and more manufacturers are turning to "hydraulic pushers". With types it is a little clear, now in more detail how they work.
The principle of operation of the hydraulic compensator
First, I want to disassemble the components of the hydraulic pusher:
- Camshaft cam
- Groove in the body of the hydraulic compensator
- Plunger sleeve
- Plunger
- Plunger valve spring
- Timing spring
- Clearance between the hydraulic lifter and the camshaft cam
- Ball (valve)
- Oil channel in the body of the hydraulic compensator
- Oil channel in the cylinder head
- Plunger spring
- Timing valve
The hydraulic compensator is like an intermediate link between the valve and the camshaft of the gas distribution mechanism. When the cam of the shaft (1) does not press on the hydraulic compensator, the valve (12) is in the closed state, by the action of the spring (6).
The spring of the plunger (11) presses on the plunger pair (3 and 4), due to this, the body of the hydraulic compensator moves to the shaft until it abuts against it, thereby dividing the clearance to a minimum.
The pressure inside the plunger is produced using oil pressure, from the engine it moves along the channel (10) and then into the channel of the compensator itself (9). Then it goes inside through the groove (2), where it bends the valve (8) and passes it creating pressure.
Then the cam of the camshaft goes down, creating pressure on the hydraulic compensator. The oil that has got inside the plow pair creates pressure on the valve (8), actually packing it. As we all know, the oil practically does not compress, therefore, after locking, the compensator acts as a rigid element that presses on the timing valve, opening it.
It is worth noting that this is a highly efficient device, the oil from the plunger pair is squeezed out a little before the ball valve (8) prohibits it inside. Thus, a small gap may form, which will be removed the next time the oil is pumped through the channels (9 and 10) and the hydraulic compensator will become rigid again.
Thus, regardless of the motor temperature, thermal expansion, the maximum possible clearance will always be set. This mechanism does not need to be adjusted for the entire service life, even in spite of the output, because it is always effectively "pressed" against the camshaft.
Pros and cons of a hydraulic expansion joint
There are many positive aspects of such a mechanism:
- It is completely out of service, it works automatically
- Increased resource of the timing system
- Maximum downforce for good traction
- Minimum fuel consumption
- The engine is always quiet
Well, in spite of all the advanced design, there are also a fairly large number of disadvantages.
- Since all work is based on oil pressure, you only need to fill high quality lubricants... Synthetics desirable
- The oil needs to be changed more often
- The design is more complex
- Expensive repairs
- Over time, they can get clogged, which worsens engine performance (consumption and traction), and the timing begins to make noise
The biggest disadvantages are that the design is expensive and complex, and VERY demanding on the quality of the oil. If you pour “don’t understand what” they will fail very quickly and require replacement. For example, conventional mechanical pushers are much simpler and less demanding on the quality of the lubricant.
Why do hydraulic lifters knock
To begin with, I would like to note if the compensators knock, this indicates that they are not working correctly, most likely they are out of order, or something is wrong with the engine lubrication.
Actually, the main reason lies in the quality and level of the oil, although there are a lot of mechanical faults.
- Not enough oil. This also happens, it is not efficiently pumped into the channels and therefore is not pumped into the plunger pair, that is, the required pressure is not created inside
- The channels in the block head or the hydraulic compensator itself are clogged. This is due to untimely replacement oil, it burns and deposits form on the walls, which clog the channels, the oil cannot effectively pass into the expansion joint.
- The plunger pair is out of order, often it just wedges
- Failed plunger ball valve
- Carbon deposits on the outside of the plunger body. He physically does not allow him to rise and compensate for the gaps.
Of course, there is a knock due to the fact that there is carbon deposits in the system, then you just need to remove them and rinse them, the performance can be restored. BUT at high mileage, they break (development appears), require replacement.
As the name suggests, a hydraulic lifter is a hydraulic mechanism in a car engine.
He is responsible for maintaining a constant working clearance in the valve ICE mechanism, since with an increase in the temperature of the engine, the dimensions of its parts and the gaps between them change.
Serviceability of hydraulic lifters guarantees trouble-free operation power unit car, including with significant temperature jumps.
It maintains the clearance of the intake or exhaust valves of the internal combustion engine at the same level, including when the timing belt is worn and valve train generally.
Ideally, during operation, the hydraulic compensator should not emit any extraneous noise - rustling, grinding or knocking.
Any such sounds indicate its malfunction and the need to diagnose the mechanism.
Ignoring the problem in the future can lead to incorrect operation of the power unit, increased consumption gasoline, rapid wear of the valve train and a critical drop in engine power.
With proper care and careful operation of the car, hydraulic lifters serve for a long time and do not require any special attention.
However, sometimes problems with this node do happen.
So, for example, if the car already has a solid mileage, when there is a natural wear of the plunger pairs of the hydraulic compensator, errors in maintenance or a significant break in the operation of the vehicle, a depressurization of the system, oil leakage and its partial airing may occur.
Such a defect appears on a warm engine with a slight knock in the timing drive.
You can try to solve this problem yourself by pumping hydraulic lifters.
Insofar as working fluid hydraulic compensators are engine oil ICE, then you need to make sure that the oil is fresh and its level is sufficient.
If everything is in order here, then the car needs to be started and, having raised the speed to 2 thousand, let it run for 2 minutes.
Then let the engine run for about 3 more minutes, changing the speed in the range from 1.5 to 3 thousand. Then release the gas pedal and let the engine run for idle about 1 minute.
For the defect to disappear, one pumping cycle is most often enough, but a repetition may also be necessary.
If, after 2-3 pumping, the noise in the timing drive remains, then it is necessary to look for a malfunction of the hydraulic compensators by diagnosing and disassembling the mechanism.
It should be noted that knocking is the most important external manifestation of a malfunction of hydraulic lifters.
It can arise for various reasons, the main ones are as follows:
- ... significant wear of the mechanism or a defect arising during operation, up to jamming, hydraulic compensators;
- ... low-quality, off-season or out-of-factory engine oil;
- ... mud deposits in the internal parts of the hydraulic lifters or irregularities in the internal combustion engine lubrication system.
The ingress of dirt and deposits into the internal cavities of the hydraulic lifters is associated, as a rule, with a poorly functioning oil filtration system in the engine, a clogged oil filter, a long period ICE operation in old oil.
Therefore, it is very important to strictly adhere to the requirements of the car manufacturer and timely change the oil and oil filter, fill in oil of the appropriate mark for the engine and the viscosity for the season.
You should also change the oil and filter after any malfunctions of the internal combustion engine, for example, after overheating, since such problems can lead to a change in the chemical properties of the engine oil.
With significant contamination of the hydraulic lifters, a characteristic knock may appear both when the engine is cold started, and after it is heated to normal temperatures.
Experts believe that the knock of hydraulic lifters that occurs on a cold engine, immediately after starting, is not a sign of their malfunction.
If the knocking disappears after the engine warms up, then this can be attributed to the normal operation of the mechanism.
At the time of starting the engine, the oil in it does not have the viscosity necessary for the hydraulic compensators, which leads to the appearance of a knock, then the oil heats up, liquefies and the knock disappears.
Cold knocking can also occur for the following reasons:
- Hydraulic lifter valve malfunction.
During engine downtime, oil can flow out of the hydraulic compensator, which leads to systematic airing of the mechanism. During warming up or pumping, the pressure is normalized and the knocking disappears; - Significant contamination of the hydraulic compensator oil passages.
The higher the oil temperature, the less dense the dirt deposits in the channels become, due to which the knocking will disappear. Here you need to keep in mind that over time, the channels can become tightly clogged, this will finally disable the hydraulic compensator, and it will knock constantly. In some cases, the use of engine oil cleaning additives can correct the situation. good quality from a trusted manufacturer; - Incorrect operation of the oil filter.
If its functional ability to pass oil is impaired, then when the internal combustion engine starts to work, hydraulic lifters may experience oil starvation, when the oil reaches its "working viscosity", the knocking will disappear, but it is still better to replace the problem oil filter.
Knocking hydraulic lifters in the engine when warmed up are considered by experts to be the most dangerous. It can be a constant knocking on a warmed-up engine at idle and under load in motion.
Diagnostics of a malfunction begins with determining the source of knocking in the internal combustion engine, because there are plenty of parts that can knock when a malfunction occurs in the engine: pistons, connecting rods, crankshaft and camshafts and etc.
The knock of the hydraulic compensator is quite characteristic - ringing, metallic, in a high tone and comes directly from under the valve cover.
For diagnostic purposes, car service specialists often use a stethoscope.
As a rule, if the hydraulic lifter knocks constantly, this indicates a critical malfunction. It is necessary to dismantle the mechanism and determine its condition.
If the reason for the knocking of the hydraulic compensator in a heated engine is contamination of the oil supply channels, then it will be enough to disassemble and rinse it. At the same time, it is recommended to revise the internal combustion engine lubrication system, replace the engine oil and oil filter.
If there is a seizure of the plunger pair, then such a hydraulic compensator must be replaced immediately.
When replacing one hydraulic compensator due to its jamming, it is better to replace the entire set so that in the future you do not have to open the internal combustion engine again to repair or troubleshoot other hydraulic compensators.
Install only prepared hydraulic lifters.
New "factory" hydraulic lifters are filled with an oil solution, it is not necessary to remove it, it will ensure trouble-free starting of the mechanism and will mix with engine oil in the future.
If a hydraulic compensator is installed after disassembling and flushing, then it must first be filled with engine oil on its own in order to avoid airing the mechanism and shock loads on the motor after starting it.
Replacing hydraulic lifters has its own technical features associated with the installation of the correct working position of the plunger pairs, therefore it is better to entrust this work to the professionals of the car service.
Moreover, the engine is the most expensive part of any car and experiments with its parts are usually expensive.
View our prices for engine repair
How much is it? The prices for such works are quite loyal. Call us and see for yourself!
| Name | Engine | Domestic | Foreign cars | |
| Search engine malfunction rub / hour | from | 1000 | 1250 | |
| Chain shoe (replacement) | from | 1000 | standard | |
| Cylinder block (boring) | from | 2700 | 2700 | |
| Earbuds (replacement) | from | 5000 | standard | |
| Hydraulic lifters (replacement) 16 valves | 16 valves | from | 2500 | standard |
| Hydraulic lifters (replacement) 8 valves | 8 valves | from | 1900 | standard |
| Valve pushers (replacement) V-shaped | V-shaped | from | - | standard |
| Valve pushers (replacement) single row | single row | from | 3000 | standard |
| Valve pushers (replacement) opposed | opposed | from | - | standard |
| Block head (repair) with / at single row | from | 6000 | 7000 | |
| Block head (flush-mounted) single row | from | 4000 | 5000 | |
| Camshaft bed cover (gluing) with / at | from | 3200 | 5000 | |
| Cylinder-piston group (replacement) | from | 5000 | standard | |
| Engine (s / y) | from | 4000 | 6000 | |
| V-shaped engine (repair) overhaul with / at | V-shaped | from | - | 25000 |
| In-line engine (repair) overhaul with / at | single row | from | 18000 | 24000 |
| Opposed engine (repair) overhaul with / at | opposed | from | - | standard |
| Ignition (setting) torque | from | 450 | 650 | |
| Motor protection (mounting) | from | 400 | 400 | |
| Engine protection (s / u) | from | 130 | 130 | |
| Carburetor (replacement with adjustment) | from | 550 | standard | |
| Carburetor (repair from a / u) | from | 1000 | standard | |
| Valve (lapping) for 1 piece | from | 300 | 500 | |
| Valve (adjustment) clearances 16 valves | 16 valves | from | 1800 | 2200 |
| Valve (adjustment) clearances 8 valves | 8 valves | from | 1100 | 1200 |
| Crankshaft (grinding) | from | 1800 | 1800 | |
| Intake manifold (s / y) | from | 1800 | standard | |
| Oil scraper caps (replacement) 16 valves | 16 valves | from | 3500 | standard |
| Oil scraper caps (replacement) 8 valves | 8 valves | from | 2500 | standard |
| Compression rings (replacement) V-shaped | V-shaped | from | - | standard |
| Compression rings (replacement) single row | single row | from | 10000 | 15000 |
| Compression rings (replacement) opposed | opposed | from | - | standard |
| Bracket for alternator (replacement) | from | 650 | 850 | |
| Valve cover (flush-mounted) | from | 550 | 600 | |
| Oil pump (s / y) V-shaped | V-shaped | from | - | standard |
| Oil pump (s / y) single row | single row | from | 1100 | 1400 |
| Oil pump (s / u) opposed | opposed | from | - | standard |
| Oil + filter in the engine without flushing (replacement) | from | 400 | 400 | |
| Oil + filter in the engine with flushing (replacement) | from | 450 | 450 | |
| Oil receiver (replacement) | from | 1100 | 1300 | |
| Chain tensioner (replacement) | from | 1000 | standard | |
| Rear engine mount (replacement) | from | 350 | 600 | |
| Left engine mount (replacement) | from | 400 | 700 | |
| Front engine mount (replacement) | from | 350 | 700 | |
| Right engine mount (replacement) | from | 400 | 700 | |
| Head gasket (replacement) V-shaped | V-shaped | from | - | standard |
| Head gasket (replacement) single row | single row | from | 3800 | standard |
| Head gasket (replacement) opposed | opposed | from | - | standard |
| Valve cover gasket (replacement) with a clean sealant | 650 | 800 | ||
| Valve cover gasket (replacement) | from | 550 | 600 | |
| Oil pan gasket (replacement) | from | 1100 | 1500 | |
| Distribution. shaft with valve adjustment (flush-mounted) V-shaped | V-shaped | from | - | standard |
| Distribution. shaft with valve adjustment (flush-mounted) single row | single row | from | 1100 | 3500 |
| Distribution. Shaft with valve adjustment (flush-mounted) opposed | opposed | from | - | standard |
| Alternator belt (replacement) | from | 350 | 650 | |
| Alternator belt (adjustment) | from | 100 | 100 | |
| Timing belt (replacement) V-shaped | V-shaped | from | - | standard |
| Timing belt (replacement) single row 16 valves | single row | from | 1500 | standard |
| Timing belt (replacement) single row 8 valves | single row | from | 950 | standard |
| Timing belt (replacement) opposed | opposed | from | - | standard |
| Air conditioner belt (replacement) | from | 350 | 650 | |
| Drive belt (replacement) | from | 550 | 650 | |
| Timing belt tensioner roller (replacement) single row 16 valves | from | 1500 | standard | |
| Timing belt tensioner roller (replacement) single row 8 valves | from | 750 | standard | |
| Video clip drive belt(replacement) | from | 650 | 650 | |
| Rear crankshaft oil seal (replacement) with the box removed | from | 200 | 250 | |
| Rear crankshaft oil seal (replacement) with box removal | from | 2100 | 3700 | |
| Front crankshaft oil seal (replacement) with timing removed 16 valves | from | 250 | 350 | |
| Front crankshaft oil seal (replacement) with timing removed 8 valves | from | 250 | 350 | |
| Front crankshaft oil seal (replacement) with timing removal 16 valves | from | 1700 | standard | |
| Front crankshaft oil seal (replacement) with timing removal 8 valves | from | 850 | standard | |
| Camshaft oil seal (replacement) | from | 750 | standard | |
| Candles (replacement) set of 4 pcs | from | 350 | 400 | |
| Glow plugs (replacement) | from | standard | standard | |
| Valve seat (replacement) | from | 550 | standard | |
| Turbine (repair) | from | standard | standard | |
| Turbine (s / y) | from | standard | standard | |
| Chain damper (replacement) | from | 1000 | standard | |
| Oil filter (replacement) | from | 150 | 150 | |
| Timing chain (replacement) V-shaped | V-shaped | from | - | standard |
| Timing chain (replacement) single row | single row | from | 1500 | 4000 |
| Timing chain (replacement) opposed | opposed | from | - | standard |
* The presented prices are indicative, valid as of 10.06.2018 and are subject to change without prior notice. It is not a public offer.
The most common malfunction modern engines- knock of hydraulic lifters. There are many reasons, most of them related to the quality of the oil. This material will tell you what to do with this malfunction and how to deal with it.
What is a hydraulic lifter and how does a hydraulic lifter work
The hydraulic compensator is a simple device for automatically adjusting the valve clearance in the valve drive, eliminating the need to disassemble the engine when it maintenance... The hydraulic compensator, in common parlance "hydric", is a miniature hydraulic cylinder that changes its length when the engine oil is pumped inside.
The oil volume compensates for the clearance between the valve stem and the camshaft cam. Oil enters the hydraulic compensator cavity through a valve with a very small hole, and comes out through the natural clearances of the valve pair. How well the “hydric” works depends on the oil flow and on the condition of the plunger pair, the absence of wear or seizure.
How to understand what exactly the hydraulic compensator is knocking
A faulty hydraulic compensator emits a sharp knock, chirp, with a frequency of half the engine speed.
A hydraulic compensator is considered to be faulty if it knocks for more than a couple of minutes after starting the engine or knocks after the engine has completely warmed up. The knocking is heard from above the engine and may be inaudible from the vehicle interior.
Why is the hydraulic lifter knocking?
Reasons for knocking the hydraulic compensator "cold" (with a cold engine):
- Too thick oil, on an unheated engine, does not fit well into the cavity of the hydraulic lifter. It takes time for the cavity to fill with oil.
- Clogged oil line or hydraulic compensator valve... Contamination appears when the quality is low or when the engine oil change period is prolonged, and it can also be products of wear of some engine parts.
- Worn or seized hydraulic lifter plunger. It happens from normal wear and tear or from the ingress of abrasive contaminants into the engine oil.
Reasons for knocking the hydraulic compensator "hot" (on a warm engine):
- Jamming of the hydraulic compensator plunger pair due to normal wear and tear or dirt. Seizures on the plunger block its movement and the hydraulic compensator completely loses its performance. The gap is not selected and the hydraulic compensator knocks.
- The viscosity of the heated oil is too low, oil flows out through the clearances of the plunger pair faster than it is supplied by the pump. Poor quality oil or too thin for this engine the oil strongly liquefies upon heating and easily flows out through the technological gaps.
3. Increased oil level in the engine, oil foaming due to stirring crankshaft or water entering the engine. Check the engine oil level and use only high quality engine oils.
The easiest way to eliminate the clatter of hydraulic lifters
The simplest and most effective way, which helps in most cases, is to add a special Liqui Moly additive to the oil. The additive flushes oil channels, removes impurities and restores oil supply to hydraulic lifters. In addition, the additive thickens the oil slightly, thereby compensating for their natural wear. The additive is added to the heated engine oil; the full effect occurs after about 500 km of run.
How else can you eliminate the knock of hydraulic lifters
- Replacing hydraulic lifters Advantages: guaranteed result. Disadvantages: expensive and long). It should be borne in mind that for some foreign cars, you first need to order parts, wait until they arrive, and sign up for repairs at the service. On most engines, replacing hydraulic lifters will require additional costs for disposable parts such as gaskets or sealant.
- Thorough flushing of the oil system with special flushes, for example: Liqui Moly. Pluses: relatively inexpensive. Disadvantages: The result is not guaranteed.
3. Perhaps, in advanced cases, you will need replacing the oil pump or cleaning the oil lines the engine with its partial or complete disassembly.
What will happen if you do not eliminate the knock of hydraulic lifters
If you do not deal with the elimination of the knock of hydraulic lifters, then you can drive for quite a long time without any problems, but, over time, the engine will run louder, with vibrations, power will decrease and fuel consumption will increase, and then there will be wear of the entire valve train, in particular the engine camshaft. Replacing it is a very expensive undertaking.
Outcome
If the knock of the hydraulic lifters repeatedly occurs, then there is no point in waiting for the worsening of the situation. The addition of the additive will solve the problem and prevent the development of wear for a long time.
VIDEO
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Thermal expansion due to heating is tricky. For example, if the valve of the gas distribution mechanism, due to the thermal expansion of the metal, lengthens so much that the end of its rod rests against an adjacent part in the timing kinematic diagram, the valve disc will not be able to sit tightly into the seat and ensure the tightness of the combustion chamber.
As a result, compression is lost, the engine does not develop power, and the valve disc, having lost the ability to give heat to the cylinder head and cool down during landing in the saddle, overheats and can burn out, which will require expensive repairs to the power unit to eliminate the malfunction.
To avoid the negative consequences of thermal expansion of the valves, gaps must be provided between the valves and their tappets. They are called thermal, which unambiguously indicates the purpose of the clearances - to protect the motor from problems associated with resizing due to different expansion of differently heated parts.
However, wear, which, in addition to valve seats in the cylinder head, sealing chamfers on the plates and the thrust ends of the valve stems, also undergoes other rubbing parts of the drive during operation, is no less insidious than thermal expansion.
With wear, the clearance set in the assembly line for thermal expansion increases. This leads, firstly, to a reduction in the period when the valve is open. The valve opens later and closes earlier, which, depending on whether this happens with the intake or exhaust valve, has a negative effect on filling the cylinders with a fresh charge and cleaning them from exhaust gases. This distortion of the valve timing causes a decrease in engine power and an increase in fuel consumption.
Secondly, due to the fact that with an increase in the gap, the camshaft cam prematurely breaks off the pusher, the valve plate begins to return to the seat not smoothly, as it should, but with a blow. And the cam of the camshaft, instead of smoothly pressing the pusher, also begins to beat on it. Impact work accelerates wear and can contribute to the appearance of microcracks on the contact surfaces, the further development of which, most likely, explains many known cases of valve seats falling out of the cylinder head. Indicates that the timing parts are experiencing shock loads, the appearance of noise.
This means that the mere presence of a thermal gap is not enough. It is also necessary to provide for the possibility of adjusting it during engine operation and prescribe this procedure as mandatory during maintenance.
But there is another way out. To get rid of the troubles associated with thermal expansion and wear, a special device has been developed that automatically selects the thermal gap in the valves and compensates for the effects of mechanical wear.
For users, the most obvious advantage of using hydraulic expansion joints in the gas distribution mechanism is that there is no need to periodically check and adjust valve clearances.
However, what was said above illustrates that it is much more important that thanks to the operation of the hydraulic lifters, the optimal valve timing remains practically unchanged and, with them, the dynamic and economic characteristics of the engine, as well as the component composition of the exhaust gases. In addition, the use of hydraulic compensators reduces the noise level from the engine, and since this indicates a decrease in dynamic loads, we can talk about an increase in the durability of timing parts.
Another name for hydraulic compensators of the thermal gap is hydraulic pushers, but it is truly true only for the units located directly in front of the valves. However, depending on the kinematic diagram of the valve drive and design considerations, hydraulic lifters can be located at other points of the drive.
In particular, in the presence of rocker arms in the valve drive, which is a two-armed lever, the hydraulic compensator is often made in the form of a support for the arm opposite to the arm that acts on the valve.
Such nuances make hydraulic lifters visually different from each other, but their constructive essence does not change from this.
The hydraulic compensator consists of a body, a piston, a spring placed between them and a shut-off valve. The spring expands the housing and the piston in different directions, as a result of which the valve clearance is selected. In the cavity formed in the internal volume above the piston, oil is supplied from the engine lubrication system under pressure and creates a backwater that provides a backlash-free kinematic connection between the valve and its drive parts during engine operation.
At the moments of pressing on the hydraulic compensator with a cam or rocker, the valve locks the oil cavity above the piston from the inside. This prevents oil from flowing back out of the cavity through the inlet. Oil losses through the gap between the housing and the piston are replenished during the "rest" period, when the cam or rocker arm stops pressing on the hydraulic compensator.
Everything has a lifespan, and a hydraulic lifter has one too. The hydraulic compensator works normally while the oil leaks from the cavity above the piston have time to be replenished during the "rest" time. But when the balance is disturbed in the direction of leaks, the drive begins to work with blows, which will declare themselves with characteristic knocks.
Oil can be squeezed out of the hydraulic lifter too quickly for two reasons. Firstly, the clearance between the piston and the inner surface of the housing has increased excessively due to natural wear, which accompanies the movement of any parts rubbing against each other.
The second reason is a malfunction of the valve that closes the internal cavity of the hydraulic lifter. For the valve, not only wear is critical, but also deposits of oil aging products.
In addition to the problems associated with oil leakage, there is another nuisance that can occur with a hydraulic compensator - seizure of the piston in the housing. As the manufacturers point out, this is the main reason for the return of hydraulic lifters during the warranty period. However, after its expiration, foreign particles trapped in the hydraulic compensator along with oil and penetrated into the gap between the plunger and the sleeve can also cause seizure.
In any case, the quality of the lubricant determines the service life of the hydraulic compensators. Hence the demand for the characteristics of the engine oil and strict adherence to the frequency of oil and oil filter changes.
But what is the lifespan of the hydraulic lifters? If you study the information of the manufacturers of these devices, it turns out that you can count on trouble-free operation only up to a mileage of 120 thousand km. Further - how the cards will lay down.
Undoubtedly, the announced figure will add fuel to the fire of disputes, which is better - hydraulic compensators or their absence and manual adjustment of thermal clearances, because, as practice shows, it may also be needed only for the specified mileage. Or it may not be necessary - this practice of exploitation also knows. Considering all the advantages and disadvantages of using hydraulic lifters, the truth, most likely, as usual, is somewhere in between.
Parts of the engine's gas distribution mechanism during operation experience heavy loads and high temperatures. From heating, they expand unevenly, since they are made of different alloys. To ensure normal operation of the valves, a special thermal gap between them and the camshaft cams must be provided in the design, which closes during the operation of the motor.
The gap must always remain within the prescribed limits, therefore, the valves need to be periodically adjusted, that is, the selection of pushers or washers of the desired size. To get rid of the need to adjust the thermal gap, and to reduce the noise on a cold engine, hydraulic lifters allow, sometimes they are called simply "hydrics" or hydraulic pushers.
Hydraulic compensator device
Hydraulic compensators automatically adjust the changing thermal gap. The prefix "hydro" implies the action of some kind of liquid in the work of the part. This liquid is oil, which is supplied to the hydraulic lifters under pressure. A sophisticated and precise spring system internally adjusts the clearance.
Various types of hydraulic lifters
The use of hydraulic lifters assumes the following advantages:
- no need for periodic valve adjustment;
- correct;
- reducing noise when the motor is running;
- increase in the resource of gas distribution mechanism parts.
The main components of the hydraulic compensator are:
Principle of operation
The work of a part can be described in several stages:
- The cam of the camshaft does not exert pressure on the compensator and is turned towards it with the back side, while there is a small gap between them. A plunger spring inside the compensator pushes the plunger out of the sleeve. At this time, a cavity is formed under the plunger, which is filled with pressurized oil through the aligned channel and hole in the body. The volume of oil is raised to the desired level and the ball valve is closed by a spring. The pusher rests against the cam, the movement of the plunger stops, and the oil channel is closed. In this case, the gap disappears.
- When the cam begins to rotate, it pushes the hydraulic lifter, moving it down. Due to the accumulated volume of oil, the plunger pair becomes rigid and transfers the force further to the valve. The pressure valve opens and the air-fuel mixture enters the combustion chamber.
- During the downward movement, some oil flows out of the cavity under the plunger. After the cam passes the active phase of action, the cycle of work is repeated again.
Hydraulic lifter operation The hydraulic compensator also regulates the clearance resulting from natural wear of the timing parts. This is a simple, but at the same time, complex mechanism with precise fit of parts.
The correct operation of the hydraulic expansion joints largely depends on the oil pressure in the system and on the degree of its viscosity. Too viscous and cold oil will not be able to flow in the required amount through the channels into the body of the pusher. Weak pressures and leaks will also reduce the performance of the mechanism.
Types of hydraulic lifters
There are four main types of hydraulic compensators, depending on the timing arrangement and the installation location:
- hydraulic pushers;
- roller hydraulic pushers;
- hydraulic supports;
- hydraulic supports that are installed under the rocker arms or levers.
Types of hydraulic lifters All types are somewhat different in design, but have the same principle of operation. Most widespread in modern cars received conventional hydraulic pushers with a flat support for the camshaft cam. These mechanisms are installed directly on the valve stem. The camshaft cam acts directly on the hydraulic tappet.
With the lower position of the camshaft, hydraulic supports are installed under the levers and rocker arms. In this position, the cam pushes the mechanism from below, and the force is transmitted to the valve through a lever or rocker.
Location options Hydraulic roller bearings work on the same principle. For less friction, rollers are used that contact the cams. Hydraulic roller bearings are mainly used on Japanese-made engines.
Advantages and disadvantages
Hydraulic expansion joints avoid many technical problems during engine operation. There is no need to adjust the thermal gap, for example, using washers. Hydraulic pushers also reduce noise and shock loads. Smooth and correct operation reduces wear on timing parts.
Among the advantages, there are also disadvantages. Engines in which hydraulic lifters are used have their own operating characteristics. The most obvious of these is the uneven operation of a cold engine at the time of start. Characteristic knocks appear, which disappear when the temperature and pressure are reached. This is due to insufficient oil pressure at start-up. It does not enter the expansion joints, so a knock appears.
Another disadvantage is the cost of parts and service. If a replacement is required, then it should be entrusted to the master. Also, hydraulic lifters are demanding on the quality of the oil and the operation of the entire lubrication system. If you fill in low-quality oil, then this can directly affect their work.
Major malfunctions, possible causes and replacement
A knock that appears indicates a malfunction in the gas distribution mechanism. If there are hydraulic lifters, then the reason may be in them:
- Malfunction of the hydraulic pushers themselves: failure of the plunger pair or jamming of the plungers, jamming of the ball valve, natural wear.
- Low oil pressure in the system.
- Clogged oil channels in the cylinder head;
- Air ingress into.
It can be quite difficult for an ordinary motorist to determine a faulty gap compensator. To do this, for example, you can use a car stethoscope. It is enough to listen to each hydraulic compensator to determine the faulty one by its characteristic knock.
Also, the performance of the hydraulic lifters can be checked if they can be removed from the engine. When filled, they should not shrink. Some types can be disassembled and the degree of wear of the internal parts can be determined.
Poor quality oil leads to clogging of the oil passages. This can be corrected by replacing the oil itself, the oil filter and flushing the hydraulic lifters. You can rinse special fluids, acetone or high-octane gasoline. If it's about oil, then this should help eliminate knocking.
When replacing hydraulic gap expansion joints, some nuances must be observed:
- The new hydraulic pushers are already filled with an oil composition. You do not need to remove this oil. The oil mixes in the lubrication system and air does not enter the system.
- Do not put "empty" expansion joints (without oil) after flushing or disassembling. This is how air enters the system.
- After installing new hydraulic lifters, it is recommended to turn the crankshaft... This is done so that the plunger pairs come into working condition and the pressure rises.
- After replacing the hydraulic pushers, it is recommended to change the oil and filter.
In order for the hydraulic lifters to deliver as few problems as possible during operation, you need to use high-quality engine oil, which is recommended in the car's manual. It is also necessary to observe the regulations for changing the oil and filter. Observing these rules, hydraulic expansion joints will last a long time.
