The internal combustion engine works as a single complex mechanism. The effective interaction of the gas distribution and crank mechanisms and with the engine lubrication system is largely provided by valve stem seals. The driver not only needs to be familiar with the functions of the parts, but also to correctly diagnose wear and the need to replace oil seals.
What are oil seals for?
The movement of the piston in the cylinder is facilitated by the splashing of oil under the skirt. But a thin film of lubricant is removed by oil scraper rings, which are dressed on the piston. On the other hand, in the gas distribution mechanism, the contact surfaces are lubricated.
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A kind of oil suspension is created under the head cover of the block. On the border of the cylinder and the cavity above it, the valve stem seals are located. Their task is to prevent oil mist and oil from the valve stem from entering the combustion chamber of the cylinder.
It is not difficult to guess, given the constant contact with the valves of the gas distribution mechanism, that the caps are under constant load. Each valve makes hundreds of movements per minute, and the oil is heated to high temperatures.
How many and where are they on the engine
Based on the purpose and work being done, it is easy to determine where the valve stem seals are located. If we consider the engine assembly, then the cap is dressed on the valve stem. Structurally, the part is a plastic part in the form of a sleeve made of a special stable material and a metal base.
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The location of the valve stem seals in the engine during its disassembly is determined as the cylinder head, at the point where the valves enter the working chamber.
If the engine has 8 valves and 16 valves
You don’t have to puzzle over how many valve stem seals are in a 16 valve engine. The number of these critical parts is exactly equal to the number of valves. Those. if in an engine with 4 cylinders it is indicated that there are 2 valves per cylinder, then there will be 8 caps. In more modern engines, where there are 4 valves per cylinder, the number of seals will be 16. Provided that the engine is 4-cylinder.
Reasons for wear
Along with the constant mechanical impact, the cap is exposed to the aggressive action of heated oil and impurities in it. Do not forget about hot exhaust gases at the onset of the exhaust stroke.
Over time, natural rubber roughens, the walls of the sleeve crack and wear out. Despite the fact that the maintenance schedule did not determine the exact interval for replacing the caps, if the corresponding symptoms appear, it is not worth delaying replacing with new parts.
How to determine if a replacement is needed
Among the main criteria that directly indicate the need to replace valve stem seals are:
Oiling the spark plug electrodes. Oil has the ability to seep into the combustion chamber.
Increased oil consumption. Compared to the traditional "appetite" of 1 liter/10,000 km, the same consumption increases to a liter for every thousand.
The appearance of blue smoke at the exhaust. Part of the oil has time to burn out during the compression stroke.
Sometimes there is a dilemma, which is the cause of blue smoke from the exhaust pipe. By mistake, wear of parts of the cylinder-piston group is often called such a reason. To finally decide whether you need an overhaul of the engine or replacement of valve stem seals, it is enough to check the compression. The normal value of this indicator allows you to confidently point to the caps.
By the way, for a short time the problem of increased oil consumption will be removed by the use of special tools. A special softening additive for valve stem seals will restore the functionality of parts for a couple of thousand kilometers. The additive is effective after 500-700 km of run after addition. Do not delay the repair, most likely similar symptoms of engine wear will appear again soon.
How to find everything you need for work
When contacting a service center, changing the valve stem seals is not difficult. However, this approach will mean for the owner of the car the option of performing work with the removal of the head of the block, which involves replacing the gasket and mounting bolts. And yes, it's a big time investment. This option means a significant overpayment.
The easiest option is to do the work yourself. To do this, it is worth preparing a tool for replacing valve stem seals and buying a set of consumables for one engine.
Which caps are suitable: sizes and price
When determining which valve stem seals are best for a particular motor, you should pay attention to the original kit. You will receive a quality product, and the price does not seem significant.
For example, a set of original spare parts for popular models costs from 1.3 thousand rubles. (Toyota Camry 2.4 l) up to 2.2 thousand rubles. (BMW X3 2.5 L). When compared with available analogues, changing valve stem seals is cheaper by an amount of 800 to 1200 rubles, respectively.
When choosing analogues, do not be too lazy to check the compliance of the parts by the VIN number, or ask the store manager for advice.
We select a puller
To successfully replace valve stem seals without removing the head, you will need to buy a special tool. As a last resort, you can borrow such a set from a neighbor in the garage.
To do the job, you will need a tool, better known as a cracker. When choosing, you should pay attention to the equipment indicating its suitability for use with a particular engine. The use of universal devices is also allowed. However, some station wagons are still designed for a certain type of engine - with an HV or SOHS layout.
The tool is designed to clamp valve springs by mechanical pressure. After removing the crackers, access to the valve stem seals opens.
Do-it-yourself removal and installation procedure
At the initial stage of the work, the car is de-energized, the ignition coil is turned off and the candles are unscrewed. The piston of the first cylinder is set to top dead center. Next, to change the valve stem seals, perform the following operations:
Remove the valve cover and all hoses. The rocker bolts are loosened.
We remove the rockers. At the same time, make sure that crackers do not scatter when removing from the axle. Do not remove the rocker arms from the axle and do not turn them over so that oil does not leak from the hydraulic compensator.
Install the puller and compress the spring. As a result, two crackers are released that need to be removed (it is convenient to use tweezers).
We remove the valve plate, we get access to the valve spring and washer.
We press out the installed part. It is possible to use either an impact collet or pliers to tighten the cap along the axis.
Before installing a new cap, check the play of the valve itself in the guide. If the indicator does not exceed 0.15-0.20 mm, install the valve back.
A new cap is put on the lubricated valve shaft using a mandrel. The spring and valve disc, crackers are returned in reverse order.
Use a torque wrench when tightening the rocker bolts. Often the tightening torque is set at 50Nm.
If it is necessary to change the valve stem seals in cylinders 2 and 3, the pistons must also be moved to the end position.
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Modern high-tech engines are poorly represented without a good lubrication system. But it is also necessary that the oil does not get into the cylinders.
What is a valve seal?
Due to such loads, the material from which the softest part is made becomes harder. Then the working edges of the part are erased. In this case, the valve stem seals will have to be replaced, the engine can also be flushed or preventive maintenance carried out.
However, one should not think that oil seals need to be changed every year. Modern manufacturers have already established a culture of production of these parts. Replacement is necessary every 100,000 km. But there are motors where replacement needs to be done more often.
What are the signs of wear on old valve stem seals? Here they can be seen even from the outside. Wear can be recognized by the bluish smoke from it. It can appear for a while only when the engine is started or when the engine is braked.
On a part such as valve stem seals, signs of wear in the form of smoke are not the only factor. The second sign is an increased “appetite” for oil. In this case, leakage of the lubricating fluid may not be observed at all. Speaking approximately, the consumption will increase to 1 liter of oil per 1000 km. Also, another sign is salting and oiling of the electrodes on the candles.
How to replace valve stem seals?
Many advise to carry out this operation in certified service stations, since the work requires disassembling the motor. You can carry out this operation without removing the cylinder head, you just have to stock up on the right amount of patience.
Set of tools
You will need some tools to get the job done. Usually required which is used when repairing the motor. We will need pliers and a special tool that will compress the valve spring. Tweezers will be needed in order to get the crackers. In addition to all this, you will need a mandrel, with which the seals will be pressed in. You also need a hammer and a rod of tin solder. The dimensions of the rod should be no more than 8 cm in diameter.
We carry out a replacement
Removing the valve stem seals involves the following steps. First you need to dismantle the cylinder head cover. Then turn the crankshaft. It is necessary to rotate until the mark on the camshaft sprocket aligns with the same mark on the bearing housing. Then remove together with the camshaft. Now you can fix the sprocket and chain. Disconnect wires from spark plugs and remove spark plugs.
At the next stage, we press the spring well and remove the valve drive lever. We derive from under the locking plate and remove the spring. Unscrew the adjusting screw. In place of the screw, you need to screw in a tool that can compress the valve spring. We insert our rod into the hole that was formed by removing the candle. This is required to keep the valve closed. Now let's release the crackers. To do this, it is usually necessary to compress the valve spring and tighten the cracker bolt. We remove the parts, remove the tool.
Now you can see the seals. If you do not know how to change valve stem seals, then you should use a collet clamp. This allows you to remove the seals with the help of light blows of the striker. Do not use screwdrivers, pliers, or any other similar tools to press out. This way you can cut the bushing.
The new part must be carefully put on the valve (and at the same time try not to damage its extreme part). The inner surfaces must be lubricated with oil. This will move the gland along the valve to the guide sleeve. Now it remains to lightly knock and finally press the gland.
After successful pressing, it's time to reassemble everything in reverse order. So you learned how to change valve stem seals.
How to choose oil seals?
Today there are practically no problems with spare parts. However, it is not necessary to exclude the situation when you have to trust not on the spare parts recommended by the manufacturer, but on those that are in stores.
If we talk about the choice of oil seals, then their main purpose is a seal for the valve stems, as well as valve bushings. These seals are supposed to protect the combustion chambers from oil. When oil seals are visible, signs of wear, it's time to take care of acquiring new ones.
You know how these elements are arranged. As the use of these parts shows, it is this solution that allows you to get good results. So, protection is maintained even when the valve stem suddenly warps.
New models of caps made of fluoro rubber or acrylate rubber are used on modern engines. However, no one ever said that they cannot be used on older machines.
If new signs of wear are installed on the old engine, they will appear much later than the deadline, and the motor itself will greatly benefit from such a move. This is the best solution if the cap fits the valve in terms of fitting dimensions.
It is also important to consider the profile of the inside of the stuffing box. For example, Japanese engines have caps that have a protrusion on the inside. There is a groove on the guide bush in this place. You should not experiment and put such parts on smooth bushings.
The long life of the caps will be ensured by the installation of new seals on new engines. If you can put new models of caps on an old motor and nothing will happen, then if you put an old oil seal model on a new ICE model, then anything can happen. The whole point here is not even what valve stem seals are according to design features, but the fact that new power plants operate in extremely harsh conditions. Old models of oil seals simply cannot withstand such loads. Therefore, their purchase is meaningless.
So, we found out which valve stem seals have signs of wear.
Today, the situation with spare parts for foreign cars is fundamentally different from what it was some 6-7 years ago, and finding the parts you need for repairs is usually not a problem. Nevertheless, in the practice of engine repair, there may be cases when you have to focus not on what is needed, but on what can be purchased.
Today we are talking about valve stem seals.
Valve stem seals, as you know, are designed to seal the mating of valve stems with guide bushings, they prevent oil from penetrating into the gap. In modern engines, this task is solved by rubber caps reinforced with a thin steel bushing and an expander spring that presses the sealing lip against the valve stem. This design, as experience shows, is the least sensitive to distortions of the valve stem in the sleeve, provides a secure fit of the cap and, when using appropriate materials (acrylate or fluoroelastomer), gives a very high sealing life - more than 150 thousand kilometers of the car. Caps of a different design, including non-reinforced ones with a wide sealing surface, fluoroplastic, etc., were installed on some engines of past years of production, but are no longer used on modern engines.
When repairing, in the vast majority of cases, it is necessary to use only those caps that are designed for this engine. However, sometimes this rule can be violated without any damage to the reliability of the engine and oil consumption. For example, modern valve stem seals can be installed on an old motor if their main mounting dimensions (first of all, the diameter of the seat belt on the guide sleeve and the diameter of the valve stem) match. Such a replacement will not only not worsen, but most likely improve the seal and make it more durable.
There are similar examples. So, the well-known manufacturer of Goetze seals for old Mercedes M102 engines produces caps of a modern design to replace the outdated ones (they are used to seal intake valves). The equally well-known company Reinz supplies spare parts for Mercedes engines of the M110 and M123 models with rubber caps instead of the "native" fluoroplastic ones, which worked satisfactorily only with unworn valves and guide bushings.
These examples show that the use of more expensive "original" spare parts supplied by the car manufacturer is not always better than what the manufacturers of these parts offer directly.
The need to replace valve stem seals with similar ones, but from a different engine, may also arise in other cases. For example, when "native" caps are too expensive - the price for some samples can reach $ 4-5 per piece. There may be situations when one of the caps is damaged due to inaccurate assembly of the head. Then the search for the same new one will lead to a loss of time (up to order delivery in ten days) and money (often valve stem seals are supplied as a kit for the engine). Therefore, for such "accidents" it is sometimes useful to know the possible outcomes, i.e. options for replacing valve stem seals with analogues, provided that the replacement does not lead to a deterioration in engine reliability.
When selecting valve stem seals, in addition to the coincidence of the already noted characteristics, it is necessary to take into account other dimensions and design features:
- the height of the "replacement" cap should not exceed the height of the "native" one by more than 0.5 mm, otherwise, at the maximum stroke of the valve, the spring plate may damage the cap; - the outer diameter of the cap should not be too large, at least the cap should pass freely inside the valve spring. This is important for those engines that have two springs installed on each valve - in this case, the internal spring limits the outer diameter of the cap; - it is desirable that the length of the seat band on the guide sleeve be close to the length of the band on the cap. If the collar on the cap is too short, then when the cap is installed too "deep" on the sleeve, it will be damaged by the edge of the sleeve, or the sleeve will press the sealing edge of the cap from the valve stem, and the seal will be broken; - it is necessary to pay attention to the profile of the inner surface of the cap. On some engines (mostly Japanese), the cap has an annular protrusion on the inner seating surface that enters the reciprocal groove on the guide sleeve. Installing such a cap on a smooth sleeve is unsuccessful, because it can be damaged due to too much tension. Caps without a reinforcing sleeve often have a similar shoulder, which is why their use is also limited, but due to the danger of jumping off a smooth sleeve; - when selecting caps, it is necessary to pay attention to the years of manufacture of engines - both the one that is being repaired and the one from which caps are supposed to be used. Older motors may have had cheaper cap materials (including limited life nitrile rubber). And in general, it is undesirable to use caps of older designs on modern engines due to harsher operating conditions, although reverse replacement is quite acceptable.If we analyze the seating dimensions of valve stem seals of various makes and models of cars (see table), it is easy to see that the vast majority of European-made engines have only two main cap sizes - 7x9.8 mm and 8x12 mm, etc., perhaps , only Mercedes, Ford and Opel engines, old Volvos and some Fiat and Alfa Romeo diesel engines. Japanese engines usually have different cap sizes than European ones (with the exception of some Nissan and Isuzu models), and we can only talk about interchangeability between them.
In conclusion, we note that domestic VAZ engines, in accordance with their European pedigree, have valve stem seals with a size of 8x10.8 mm. This fact allows us to use valve stem seals on our motors from their main global manufacturers - AE (Payen), Elring, Glazer, Goetze, reinz and others. True, we still do not recommend the way back - namely, the installation of domestic-made caps on foreign cars, as they did in the recent past, when there were very few spare parts for foreign cars in Russia - the quality of domestic products is still noticeably inferior to foreign ones. Although fakes for foreign firms are also not uncommon in our country. But this is a topic for another conversation.
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Alexander Khrulev, candidate of technical sciences,
directors of the company "AB-Engineering"
Quite often you have to notice that increased smoke appears from the exhaust pipe of a car. Sometimes situations reach the point that the car is literally shrouded in clouds of thick smoke. It is quite obvious that for every motorist the appearance of excessive smoke indicates the appearance of certain problems with.
We note right away that not always, but often increased smoke indicates serious. At the same time, it will not be difficult for experienced drivers to determine the cause by the color and composition of the exhaust. However, for beginners, it is not always easy to understand why the engine smokes, as well as to establish the cause and identify rings or caps. Let's figure it out.
Read in this article
White or black smoke from the exhaust pipe
Let's start with the main types of smoke for a better understanding of the problem. So, white smoke from the exhaust pipe is quite normal for cold engine warm-up modes. Moreover, it is a mistake to believe that it is smoke. It's actually steam. Vaporized water is a natural product of the motor.
In a cold exhaust system, this vapor partially condenses and becomes visible, and water usually appears at the end of the exhaust pipe. As the engine warms up, condensation decreases.
The colder the environment, the denser the steam. At temperatures below 10 ° C, steam is also formed on a well-heated engine, and in frost at minus 20 - 25 degrees it acquires a thick white color with a bluish tint. Humidity also affects the color and saturation of steam. The larger it is, the thicker the steam.
Note that if steam is visible in the warm season, it is quite possible that this is due to. Its shade depends on the composition of the coolant, weather, light, and also on the amount of coolant in the combustion chamber. Sometimes it can take on a bluish tint, resembling "oily" smoke. But, unlike oil smoke, which leaves a bluish haze in the air for a long time, the vapor quickly dissipates.
It is quite difficult for an inexperienced motorist to determine by appearance what is the source of smoke. In this case, you can use a proven verification method. To do this, on a well-heated engine, briefly close the cut of the exhaust pipe with a sheet of white paper, while the condensed vapor in the form of water droplets will gradually evaporate when it hits the paper and will not leave obvious greasy marks.
If this simple test confirms that it is steam and not oil smoke coming out of the exhaust system, then you need to take measures to eliminate the problem that contributes to the penetration of coolant into the cylinders.
Most often, liquid can enter the cylinders through insufficient traction (in winter, coolant leakage is often observed at the junction of the block and head), burnout, and less often as a result of formation. By opening the radiator cap or, it is easy to detect the smell of exhaust gases and an oil film on the surface of the coolant.
All problems associated with white smoke from the exhaust pipe require the elimination of not only direct causes, but also a mandatory check of systems that can affect their appearance: the switch on sensor, the clutch or the fan itself, the condition of the radiator, its plugs, hoses or connections. If white smoke and its accompanying defects are noticed, then the car cannot be operated, as the defects progress rapidly.
- We go further. Black smoke from the exhaust pipe indicates a re-enrichment of the fuel-air mixture or a deterioration in the combustion conditions of the fuel. Therefore, we are talking about malfunctions. Such smoke is usually clearly visible against a light background and represents soot particles - products of incomplete combustion of fuel.
Black smoke is accompanied by high fuel consumption, often poor starting, unstable engine operation, high exhaust toxicity, and often loss of power due to a suboptimal air-fuel mixture.
It is important to understand that monitoring the symptoms and quickly identifying the problem will further reduce the cost of repairs and avoid serious and rapidly progressing engine breakdowns.
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Why are piston rings stuck? The main signs for self-identification of a malfunction, diagnostics. Do-it-yourself piston ring decoking.
In the design of any engine, both a domestic car and a foreign car, there are valve stem seals (valve seals).
They are always involved when the machine is running, and therefore wear out very quickly. Increasing their service life is a headache for engineers working at automobile plants, but timely diagnosis of signs of wear on valve stem seals, as well as their replacement, is already the task of motorists. You can successfully deal with it only in one case, when these very signs are known to you, and if not, then this article will help you.
How do valve stem seals work and when are they considered worn?
As you know, the valve in the engine is located in two different cavities. One of them implies the presence of engine oil in it, the other, on the contrary, must be isolated from it. In this case, the valve during its operation is in constant motion. In order to maintain the tightness of the hole through which it moves from one medium to another, valve stem seals are just what is needed. They are made of special elastic rubber, however, this rubber tends to age, harden, dry out and collapse over time, as a result, the caps no longer cope with their task and begin to need to be replaced. The car owner can determine this moment by special signs.
The main signs of wear of valve stem seals.
- Increased oil consumption - if engine oil is consumed in your car more than it should be, then somewhere it is used in vain, as an option - it enters the combustion chamber due to worn valve seals.
- Oily - a consequence of the fact that oil enters the cylinders.
- when the car warms up, the engine heats up - the smoke disappears. Such a phenomenon is a clear sign of a cracked cap, which, heating up to a certain temperature, becomes wider and again begins to successfully cope with the functions assigned to it.
However, be extremely careful, these signs may indicate not only worn valve stem seals, but also other problems with the engine! Therefore, at the time of diagnosis, do not forget to pay attention to:
- mileage - as a rule, oil seals need to be replaced every 70-80 thousand km. run;
- - if it is reduced, but you did not find any leaks or problems with the valves and / or rings on the pistons, then the problem is definitely in the caps. They should be replaced.
Consequences of driving with worn valve stem seals.
If you missed the moment of failure of the valve seals, then most likely it will lead to the following consequences:
- increased oil consumption, which, firstly, will not have the best effect on your budget, and secondly, will provoke periodic oil starvation, leading to increased wear of parts and the need for premature engine overhaul;
- oiliness and eventually failure of spark plugs;
- valve burnout - soot will form wherever there is oil, including on the walls of the cylinders, which over time will interfere with the closing of the valves and lead to their burnout.
To prevent all this from happening, carry out a timely replacement as soon as you notice the first signs of wear on the valve stem seals.
We will not consider the procedure for replacing valve stem seals now, this is the topic of a separate article, but in the end we will name the main recommendations that will save you from mistakes. There are only 3 of them:
- to crack the valves, always use a special tool - a cracker, so you will be less likely to break or lose something;
- when changing caps, cover all holes on the engine with a rag or foam rubber, they will protect open cavities from dirt, and you from losing crackers;
- Be sure to lubricate the new cap with oil before installing.
And remember, if you do not have enough experience and knowledge in replacing valve seals, if you notice signs of wear, do not experiment, but give your car into the hands of professionals, they will quickly replace the failed parts with new ones and take a little in this case. Depending on the car and the service station, the costs will range from 7 to 20 thousand rubles.
Video.
