What are oil seals? Valve stem seals: functions, malfunctions and replacement How valve stem seals work.

Insufficient closing of the valves leads to the appearance of varnish deposits in the cylinder head and on the piston group.

Criteria indicating wear of oil seals:

• regular appearance of soot on spark plugs;
• excessive consumption of engine oil;
• lack of stable idle speed;
• with a sharp increase in speed - copious emission of gray smoke.

Walkthrough Maintenance includes regular replacement of oil, air, oil and fuel filters. Valve seals are designed for vehicle operation up to 100,000 km. In fact, it is necessary to carry out the replacement earlier than the specified resource.

The device of valve stem seals (valve seals)

The oil seal has the shape of a cylinder with a truncated cone. For tight contact with the surface of the valve guide, a polymer ring with an expander spring is provided. A plastic (or rubber) ring removes excess oil when the valve stem moves, and the spring allows it to be tightly fixed on the stem.

For a long time, a rubber ring was used in the design of the stuffing box. Rubber and fluoroplastic options have appeared recently. This is due to the fact that rubber tans faster and loses its properties. Manufacture of the ring using modern polymers extends the life of the stuffing box.

Purpose of oil scraper caps

Long-term uninterrupted operation of the internal combustion engine is ensured quality lubricant rubbing parts. The oil distribution mechanism provides oil supply in a small volume. Camshafts in the cylinder head and piston group - need constant lubrication. The shaft rotates and a cloud of oil forms around it. The amount of lubrication is regulated by oil scraper caps.

Carbon deposits on the valve surface lead to incomplete closure and gap formation. In the combustion chamber, the combustible mixture ignites, and excess oil settles in the form of varnish deposits. When the valve is lowered down, the stem seal prevents excess oil from entering. Protects the piston group from plaque that occurs during the combustion of oil and fuel mixture. Oil seals are considered consumable items, as they need to be replaced periodically.

The location of the oil scraper caps in the engine

The head with camshafts and valves is mounted on the cylinder block. The valve stem moves through the guide bush. The thermal gap between the leg and the sleeve is closed with caps. The oil seal is positioned so that oil from the head does not enter the combustion chamber. The camshaft journals receive oil under pressure, and the rest of the nodes - due to splashing. Having removed the engine block head and camshafts, you can see the location of the seals in the valve seats.

Signs of worn valve stem seals

You can find out about the need for replacement without disassembling the engine. Have valve stem seals the following signs of wear:

• excessive oil consumption;
• bluish smoke;
• soot on spark plugs.

Worn seals increase oil consumption. This also happens when the piston group is "coked", but there is a visual difference. Visible oil streaks on the breather pipe. Blue-colored smoke exhaust is a sign that oil is entering the combustion chamber. "Tripling" of the engine and soot on the spark plugs are justified by the flow of oil through the stem seal. The car needs diagnostics and replacement of oil seals.

The service life of oil scrapers does not depend on the price and manufacturer. For budget and "premium" auto-resource is designed for mileage up to 100,000 km.

Oil seal replacement procedure

1. Disconnecting the air filter, removing the cover and air ducts. Branch pipes and technical openings are closed with plugs. Remove spark plugs and cylinder head bolts.
2. The piston in the first cylinder is set to top dead center. Removing the lock washer and star. The valve locknuts are released, and the adjusters are unscrewed to the stop.
3. Crackers and springs are removed. The puller removes the seals. The bushings are lubricated with oil, put on the rod and installed with a hammer and a frame.
4. Assemble components and parts in reverse order. After, the rest of the caps are changed in a similar algorithm in the order of cylinders 4 - 2 - 3.

Servicing each cylinder requires a 180 degree crankshaft rotation.

Self-replacement will require a special tool. The main specific device is the "raskuharivatel" of the valves. You will need it to replace the valve seal. Devices and materials:

• sets of socket and cap keys;
• head extension;
• rod and hammer;
• Collet clamp;
• pressing frame;
• tweezers;
• head gasket;
• set of new caps;
• sealant.

During the work, it is possible to replace the gaskets under the block and cylinder head. New oil seals are selected for a specific engine model.

Procedure for replacing valve stem seals

Consider how the valve stem seals are replaced by 8 valve engine without head removal

1. Remove the fuel pump and air filter.
2. We turn off the battery power and dismantle the ignition distributor.
3. We unscrew the top cover of the block, disconnect the toothed pulley and mass.
4. Evenly unscrew and remove the fastening nuts on the camshaft and bearings.
5. We dismantle the shafts and seals.
6. By turning the crankshaft, we raise the piston to TDC on the serviced cylinder.
7. We insert a soft tin rod under the valve through the hole for the candle.
8. We remove the springs with a special device and remove the plates. We replace the seals by pressing the old ones from the bushing and installing new ones.
9. We assemble in the reverse order. We proceed to a consistent similar replacement on the remaining cylinders.

Before installation in the frame, the caps are lubricated with oil. They are pressed into the plate carefully, without sharp strong blows.

Gaskets and seals are installed under the bolt heads. Sort small items to avoid losing them.

After replacing all the valve seals, assemble the head by placing it on the sealant and a new gasket. Tighten the nuts with a certain torque, according to the instruction manual for this engine.

For different engines, valve seal kits differ in design. Installation is carried out according to technical recommendations for a specific car model. When carrying out work yourself, adhere to the accuracy:

• coincidence of the diameters of the sleeve belt and the valve stem;
• the length of the seats of the guide sleeve and cap;
• installation on oil with reliable fixation (without the slightest backlash);
• selection of a set of caps for a specific engine model.

A high class of accuracy in the manufacture of parts allows you to increase the density of the connection and the complete coincidence of dimensions.

On sale there are additives for the restoration of oil seals. Their principle of operation is to soften the hardened rubber of the o-ring. Manufacturers differ in the quality of additives. There are different effects on rubber: no effect or excessive softening, which leads to excessive consumption of oil.

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 lever valve drive. 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 on old motor you can put new models of caps and nothing will happen, then if you put the old model of the stuffing box on the new model of the internal combustion engine, 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.

Among possible causes increased oil consumption can be noted, in order of difficulty of elimination:

1. oil leaks through leaks in gaskets, seals, as well as cracks in the engine crankcase, cylinder block, oil pressure sensor, etc.
2. oil seal wear
3. wear of the cylinder-piston group
4. oil burnout due to its poor quality

The first group of causes is determined by visual viewing. Eliminating such causes, with the exception of the HEAD gasket and cracks in the cylinder block, is quite simple. It is only necessary to replace defective parts (seals, gaskets). The exception is here - the head gasket and the cylinder block. To replace them, it is necessary to remove the camshaft (with all the ensuing consequences), and then the head itself; and then completely disassemble the engine. Of course, such an operation will not be difficult for an experienced mechanic, but for an ordinary motorist ...

The second reason is the wear of low-removable caps. We will talk about the signs of the need to replace them a little lower. This operation also implies, as a rule, the removal of the camshaft (one or more - depending on the car model). However, there are cars on which this is not necessary. However, these are quite rare cases.

Finally, the wear of the parts of the cylinder-piston group. To eliminate it, it is necessary, as they say, to overhaul the engine. As a rule, it is timed to coincide with other repair operations, namely: replacing crankshaft liners, repairing (grinding) crankshaft journals, replacing valves, replacing / reaming valve guides, not to mention replacing worn (by that time) valve rockers , valve springs.

Here we look at signs that indicate symptoms similar to wear and tear. valve stem seals. Here is a list (perhaps incomplete):

Alarm malfunction

Smoky exhaust when regassing

Increased fuel consumption

Drop in power and throttle response, dips in engine operation,

Oil gets dirty quickly

glow ignition

Note that it is not necessary that all signs appear at the same time.

Smoke from the oil filler neck*

Which can sometimes be seen, for example, if the oil filler neck is opened on a running engine. On a good (i.e. serviceable) engine, air will simply come out from there (as an option - with an admixture of oil mist, which is not a malfunction). If the engine consumes a lot of oil and strong smoke comes out of the neck, then the piston group is worn out. If the engine consumes oil, and it is clean from the neck, then the matter may be (but not necessarily) in the valve stem seals.

* So this symptom is more likely not indicative of wear on the valve stem seals.

The threaded part of the candles is coated with oil

This is also one of the symptoms of the need to replace valve stem seals. However, not always. Those. it happens that the caps already require replacement, but the threaded part of the candles is still dry. For there is still not too much oil getting into the combustion chamber, it has time to burn out.

Why is the threaded part of the candle covered with oil under the conditions when it enters the combustion chamber? It would seem that if there are gaps in the thread between the spark plugs and the block head, then they are minimal and do not exceed 0.2 mm?

Consider the process of the engine. The fact is that at the moment of inlet of a portion of the combustible mixture, oil enters the cylinder, while there is a vacuum in the cylinder (as well as in the threaded gaps of the candles). The mixture is then compressed. Naturally, it (including the oil and gasoline contained in it) begins to penetrate into all places where it is possible, including the threaded gaps of the candles. The mixture is then ignited and burned. It burns almost everywhere, except, just, for threaded gaps. For they are very small (in the region of 0.1 ... 0.3 mm), as a rule, combustion cannot spread into such small gaps. As a result, oil accumulates in the threaded gaps. Gasoline evaporates, because the candles are heated.

Candles are covered with black soot. Increased smoke from the exhaust pipe

Nagar can (but not necessarily) be oily. As a rule, when the valve stem seals are worn, it is terry. Although, too rich a mixture can also give terry black soot. Blue-gray, sometimes black smoke from the muffler indicates wear of the cylinder-piston group, as well as an excessively rich mixture.

However, similar symptoms are also observed when the valve stem seals are worn out (blue exhaust during regassing), the ignition system malfunctions (the ignition timing is incorrect, the high-voltage wires, the distributor cover, the slider, etc. are “broken”, and also, possibly, a malfunction ... alarm), violation adjustments of the fuel supply system (for example, carburetor, injectors, etc.).

Those. black smoke from the muffler and black-coated candles are far from always evidence of an overly rich mixture. Both of these signs also appear both when the valve stem seals are worn out, and when the ignition system is disturbed. Why?

Because if the ignition system malfunctions, the spark on the candles will be defective, although in appearance it may be quite acceptable. Accordingly, the combustion of the oil-fuel-air mixture will also be defective. In particular, the oil and gasoline contained in the mixture will burn WORSE (than with a good spark), i.e. black soot will form, giving the appearance of an overly enriched mixture. For example, this is exactly what was observed in the case when it was “cunningly” broken.

Alarm malfunction

It can also be the cause of carbon deposits on spark plugs if circuits related to ignition pass through it. A common case is when some connectors in the alarm have bad contacts (when they are old and / or made of Chinese metal). In this case, the ignition will be either excellent, or “not very”, then (for a fraction of a second) it will be completely absent. And so - all the time.

There was a case when the car periodically stalled on the move after 10 ... 20 minutes of driving. And after - flatly refused to start. However, after a 10 ... 15 minute parking incident, it started up, as if nothing had happened and drove as long as necessary.

Note: exactly the same behavior of the machine in another case was the result of a malfunction of the valve stem seals.

In addition, the car often (but not always) stalled when trying to move uphill. The recommendations of the servicemen to repair the power system, of course, did not lead to anything at all. They only cost Money and time for reflection. However, the problem was completely removed after the restoration of electrical contacts in two alarm connectors (by removing them and lightly crimping the connectors).

Why did the car start after 10 ... 15 minutes of parking? Because during this time the signaling unit cooled down a little, the contact parts of its connectors slightly changed in size (under the influence of thermal constriction), slightly shifted relative to each other (i.e., the “male” connector was slightly displaced relative to the “mother” connector ”), there was a sort of scratching, slippage of their contacting surfaces relative to each other, and contact was restored again for some time.

Why does the engine sometimes stall when driving uphill? Because in the alarm unit located under the dashboard, when the orientation of the machine relative to the vertical changed, the alarm unit moved slightly to a different position, as a result, the electrical contacts were sometimes broken. And when the car moved to a horizontal surface, contacts were restored.

Smoky exhaust when regassing

Symptoms of the formation of smoky exhaust during regassing are similar - both in the case of a malfunction of the valve stem seals, and in the event of a malfunction of the cylinder-piston group. The difference is that if the caps are faulty, then repeated regassing (4 ... 7 times) usually leads to the (temporary) disappearance of smoky exhaust. Those. There is usually no permanent smoke. Whereas in the event of a malfunction of the cylinders and pistons, the smoky exhaust DOES NOT DISAPPEAR after several regassings.

The reason is that in the first case, the oil accumulated near the junction of the edge of the valve stem seal and the valve stem, as a result of a sharp pressure on the gas pedal, is TEMPORARILY sucked out through the gap between the valve stem and the guide sleeve, into the cylinder, which leads to several smoky exhausts at regassing. When all the nearby oil has been sucked out, there will be no smoky exhaust (until the oil accumulates again). Whereas in the latter case, oil enters the cylinder, regardless of whether the gas pedal was sharply pressed or not; no matter how many times and with what frequency it was pressed.

When idling, when the cylinders and / or pistons are worn, the smoke will be thick and bluish (like old Soviet motorcycles, Druzhba-type chainsaws), while when the valve stem seals are worn, it will (at first) seem to be “bluish”. If you look at the exhaust pipe from above with the engine running, it is not always visible. But looking ALONG the exhaust pipe, when viewed from behind the car, sometimes (but not always) makes it possible to see such a bluish haze.

Also, if, when the engine is HOT, white smoke comes out of the muffler, then this is also a sign of wear of the valve stem seals, but not of the cylinder-piston group. By the way, another reason for the appearance of white smoke on a warm engine is the ingress of coolant into the engine cylinders due to a malfunction of the head gasket.

Note that the appearance of white smoke disappearing after warming up on a COLD engine, on the contrary, is a completely normal symptom. After all, as a result of the combustion of the fuel-air mixture, in particular, water is formed. The vapors of which become visible until the engine and muffler warm up. For the same reason, water drops can even fly out of the muffler. It often happens that water drips a little from the end of the muffler pipe.

When the muffler warms up, the water vapor on its walls will no longer condense - and the white vapor will disappear. The water will stop dripping.

Too rich a combustible mixture will also give an exhaust of increased smoke, including during regassing. Which, it seems, SHOULD NOT disappear after repeated regassing.

However, in fact, not everything is so simple. There was a case when, due to a too rich fuel mixture, the car engine started with great difficulty "hot" (whereas "cold" started with half a turn). After repeated re-gassing, the exhaust of increased smoke (blackish) DISAPPEARED. However, the problem was - it was in an overly enriched fuel-air mixture.

Increased fuel consumption

The fact is that the oil that enters the cylinders during engine operation makes it difficult for the combustion of the fuel-air mixture. Accordingly, in order to remove the required power from the engine, a larger amount of mixture will be needed than in the absence of oil in the mixture.

By the way, not only valve stem seals, but also almost all other engine malfunctions also lead to increased fuel consumption, whether it be wear of the cylinder-piston group, a malfunction of the ignition or alarm system, or a non-optimal composition of the combustible mixture.

Loss of power and throttle response, failures in engine operation

This manifests itself in reduced dynamics when accelerating, overtaking. And also there may be "failures" when you press the gas pedal. Those. you press the gas, and the car SOMETIMES, instead of jerking forward, it seems to slow down, the engine stalls. If you release the gas pedal or press it SLOWLY, the engine runs normally. In such cases, it is usually recommended to adjust or repair the fuel supply system. More advanced ones also recommend paying attention to the ignition system.

This is often true, but not always. Sometimes - with a sharp increase in vacuum during the intake stroke of the fuel-air mixture (which is the result of a sharp pressure on the gas pedal), this vacuum is transmitted through the valve guides to the valve stem seals. If they are worn out, then a portion of oil is sucked in, which enters the cylinder, filling the spark plug, i.e. (at first - temporarily, and then - permanently) turning it off from work. This explains the "failure" in the engine. If the car is equipped with a catalytic converter, it "for some reason" will soon fail.

Oil gets dirty quickly

Yes, this is also one of the symptoms of valve stem seal wear, which is far from known to everyone. Why does the oil become contaminated, becoming dark, then black? There are usually two main reasons for this:

1. wear of engine parts and the ingress of wear products into the oil
2. soot formation caused by the combustion of oil contained in the fuel-air mixture and its subsequent flushing

Well, quite banal reasons, for example, a malfunction (or absence) of the air filter, as a result of which dust from the air enters the cylinders, which causes oil pollution or simply low-quality oil that quickly collapses when the engine is running, we will not consider here.

The first is generally known. But, at the same time, there should be metal particles on the magnetic oil drain plug. And if there are few or none at all?

Then, obviously, the black particles that cause the oil to darken are nothing more than coke washed off the cylinder walls. Indeed, most modern motor oils contain fairly effective detergent additives that help wash off carbon deposits. If not for them, then as a result, the piston rings would simply coke. Fast. Well, their presence in the oil saves, thereby, the engine. True, the whole blow is taken by the oil, which quickly becomes contaminated.

Since soot is formed GRADUALLY, its particles are very small in size, they, being washed off from the walls of the cylinder, freely pass through oil filter and for this reason remain in the oil, causing the need for its accelerated replacement.

However, too rich a mixture can also take place here. Which also gives black soot on spark plugs, as well as on the surface of the cylinder. Accordingly, after this soot is washed off with oil, it will enter the engine crankcase.

glow ignition

It is expressed, in particular, in the fact that the engine continues to run for several seconds, or even more, even after the key has been removed from the ignition. Yes, and this can also be a symptom of oil getting into the combustion chamber, including as a result of a malfunction of the valve stem seals. Why?

Because modern gasoline cars, perhaps, without exception (both carburetor and injection) are equipped with a fuel cut-off system when the ignition is turned off. For example, if we talk about carbureted car, then in carburetors, as a rule, there is an idle solenoid valve that shuts off the flow of the working mixture when the ignition is turned off.

By the way, for reference, a modern gasoline car does not have to be injection at all. For example, many military vehicles are, as before, carbureted. The reason is probably clear to you: military vehicles are required, among other things, increased reliability and high maintainability even in the "open field". It is clear that a knowledgeable person will be able to clean and adjust the carburetor quickly and in almost any conditions, while for adjustment injection engines can't do without a computer. Well, cleaning nozzles in the "field" is definitely impossible without special equipment. And, in fact, the military will not carry a diagnostic computer and other devices with them just to use the injector, when it is quite possible to get by with a carburetor that has proven its reliability and quick maintainability. Well, which slightly increases fuel consumption, slightly increases the toxicity of exhaust gases. And, nothing more.

Then, the more electronic parts in the car, the higher the probability of their failure, for example, when exposed to an electromagnetic pulse.

So, if even when the gasoline supply is turned off at idle, the engine continues to work, therefore, there is something in its cylinders that can burn out. In this case, it is nothing but oil. Located there in SUCH concentration at which the engine is still able (but not always) to work. It is clear that when the caps are even more worn out, even more oil will enter the combustion chamber, then the glow ignition may disappear. But, at the same time, the car will be difficult to start, there will be increased oil consumption, etc.

The car is difficult to start "hot"

If it is difficult to start “cold”, then the reason is often not at all in the valve stem seals. There, most likely, more obvious reasons, such as wear of the cylinder-piston group, fuel supply failure, ignition malfunction, including, as already mentioned, alarms. And also - a malfunction of the battery, starter.

But if “on a cold” engine it starts with half a turn, but on a hot one, paradoxically, you have to spin it with a starter for 5 ... 10 seconds or even more (or even the car’s engine stalls as soon as it warms up well), then the reason for this may well be be worn valve stem seals.

The fact is that in a cold engine, the oil is also, of course, cold. And having a high viscosity, and therefore - reluctantly leaking into the gap between the valve stem and the working edge of the valve stem seal. When the oil warms up, its viscosity decreases (sometimes by several orders of magnitude), and it is much easier for it to pass into this gap.

However, a violation of the composition of the combustible mixture, ignition malfunctions, alarms are also not excluded, of course.

Exhaust gas has a very disgusting, suffocating smell.

It is clear that the smell of exhaust gas cannot be called natural, pleasant and safe.

However, having sniffed, say, cars driving in the United Arab Emirates (UAE), I concluded that the situation with exhaust gases is MUCH (!) Better there than in Russia. It seems that a continuous stream of cars is driving, and the exhaust smell is insignificant ... Sometimes, even leaning close to the exhaust pipe, you somehow do not catch that nasty smell that comes from Russian cars. One of the reasons for this, of course, is better gasoline. Which, by the way, was also much cheaper than in Russia, at least until the ruble was sharply lowered against the dollar and many other currencies.

Yes, after all, after all, exhaust gas, what to expect from it. However, when the combustible mixture is of poor quality, incorrect (in particular, as a result of a large amount of oil in it), then, naturally, the smell of the exhaust becomes much, much more disgusting. In such cases - it is worth standing a little near the exhaust pipe when the engine is idling - and you want to get away from this smell somewhere. The neutralizer, we repeat, at the same time fails very quickly.

Therefore, if the exhaust of a car has become somehow especially unpleasant, suffocating, not the same as it was before, you should pay close attention to engine parts through which excess oil can enter the combustion chamber. In particular, these are valve stem seals.

However, a very rich combustible mixture can also be the cause of such a smell.

Worn valve guides, valve stems

Of course, the wear of their working surfaces in itself does not indicate the wear of the valve stem seals. He simply speeds it up, and significantly. It also makes it useless to replace the caps with new ones.

The fact is that if the holes in the guide bushings and / or valve stems are badly worn out, even a new high-quality valve stem seal will not be able to fully retain oil during engine operation. Which will enter the combustion chamber, as with worn caps.

So if, after replacing the valve stem seals, those symptoms of wear remain, then you should think about repairing (replacing) the valves and their guide bushings. And even about the overhaul (replacement) of the engine, because, as a rule, by such a time, its other parts also partly exhaust their resources. It makes no sense to change only the bushings and valves, if after another 20 ... 30 thousand the chain, sprockets (pulleys), rockers, pistons, rings, as well as cylinder boring, grinding of the crankshaft journals are to be replaced.

How to measure play in valve guides? If roughly and roughly, then the backlash can be considered large if, when the valve stem is swaying from side to side, it feels much higher than it was on a new (refurbished) engine. If it is much higher than the typical felt backlash for a particular engine model. Well, for a more accurate measurement, of course, you need to remove the block head, get the valves, etc.

Engine valves operate under very difficult conditions. From above, the camshaft constantly acts on them, creating a lot of friction. And from below they are in the environment of high temperature of exhaust gases. The camshaft, perhaps more than other parts of the engine, is lubricated with oil, as a result, it also gets on the valves, through which it flows down to the combustion chamber. If you do not prevent this process, the following will happen. The oil will mix with the air/fuel mixture in the cylinders and burn. This will lead to the formation of carbon deposits on the walls of the combustion chamber, on the pistons and piston rings - coking. The wear of the engine will increase and the characteristics of its operation and the quality of the combustible mixture will deteriorate. But the biggest problem is that soot forms on the valve seat and its head (on top of the flat part, the so-called “skirt”). The valve stops closing. Such a malfunction is a serious malfunction of the engine, which in a short time causes it to become inoperative.

Where are the oil seals

To prevent oil from entering the combustion chamber, valve stem seals (they are also valve stem seals) are installed on the valves. Confusing valve stem seals with oil scraper rings will only work in the name. How to find out, oil seals or rings? The caps are small rubber seals, and the rings are large thin metal formations that fit perfectly into the grooves of the pistons (crank mechanism). While the valve stem seals are located where the valves and guide bushings are located, between them (and this is already a gas distribution mechanism).

The valve stem oil seal is essentially a consumable in a car, but replacing such an element is equivalent to an overhaul of the engine, since it is impossible to change it without disassembling the internal combustion engine.

How many valve stem seals are in the engine? There are exactly as many of them in the engine as there are valves. That is, if it is an eight-valve internal combustion engine, then there are eight caps, respectively. As the valve moves to open and close the inlet/outlet, the cap removes excess oil from the stem (the narrow long part of the valve) so that the seating surfaces (that is, the part of the valve that interacts with the chamber) remain dry. Oil seals are made of rubber, which wears out quickly under the influence of an aggressive environment.

Signs of wear on valve stem seals

Like any consumable, the stuffing box has its own regulated use time. The resource of valve stem seals is 100,000 km. But as practice shows, oil seals become unusable before the regulated time. This is evidenced by the appearance of the following problems:

• the formation of soot on spark plugs,
• decrease in engine oil level,
• the appearance of blue smoke from the exhaust pipe when you press the gas pedal hard.

Location of valve stem seals

The most optimal solution is to install valve stem seals recommended by the manufacturer of this vehicle.

Such symptoms on a car give reason to think about replacing valve stem seals. Of course, it is better to do this in specialized car services. The price of replacing valve stem seals will fluctuate around 4-8 thousand rubles. How much do oil seals cost? Relatively inexpensive, about 500 rubles each. Now you can calculate how much it costs to replace valve stem seals. You can do the operation yourself. But note that the seals are easily deformed if not handled properly.

The first thing to do is to select the desired valve stem seals. Acrylate rubber is a more modern material than fluoroelastomer. The size of the valve stem seals can be calculated by measuring the diameter of the existing valve - this is for the inside. As for the oil seal models (the external size can also be attributed here), new ones can be installed on the old internal combustion engine, but not the best option on the new outdated ones.

Replacing valve stem seals with your own hands

For work you will need: a set of keys, a valve cracker, pliers for oil seals, a mandrel. It is most convenient to change the oil seals on the dismantled cylinder head. It is possible to remove the valve stem seals without removing the head. To do this, it will be necessary to set the top dead center for each piston when removing the seals from the valves. Otherwise, the valves have every chance to fall into the cylinder, even if you hold them, besides, when installing new caps without a stop, it will be extremely inconvenient.

Oil seal replacement procedure

So, how to change oil seals? The TDC is set or the cylinder head is removed. For the job, it is best to use a special tool to replace the valve stem seals, but we will also look at how to remove the valve stem seals without a puller. With the help of a cracker, the valve plate and spring are removed. Next, the oil seal is dismantled with special pliers for valve stem seals (some use pliers as a do-it-yourself valve stem seal remover, but you should take into account the risk of damage to the valve stem when using a non-specialized tool). A new oil seal is hammered with a special mandrel for valve stem seals (the mandrel can be replaced with a metal tube of a suitable diameter, but it is highly undesirable). For easier movement, the stem and the inner surface of the rubber element can be lubricated engine oil. The blows should be gentle and accurate, since this part is fragile, subject to deformation. A dull sound indicates the installation of the valve stem seal in the seat. The same is done with the rest of the valves. After the new valve stem seals are installed, the return mechanism is dried back, the cylinder head is assembled, and other attachments are returned to their place. Operation completed.

Finally

After replacing valve stem seals

To increase the life of the oil seals, special additives for valve stem seals are used. Some of them act on the rubber part, softening it, others are aimed at sealing the resulting gaps. If the use of additives to restore valve stem seals still has its effect, then restoring valve stem seals removed from the engine does not make sense at all, since their service life will be short-lived, which means that in the near future you will have to spend money on replacing them again, which is completely unprofitable.

If after replacing the valve stem seals the problem could not be resolved, this means that the replacement was not done correctly (rarely) or the malfunction was different (often).

A common question from car owners: “Why does the car smoke after replacing valve stem seals?”. Most likely, it was not the caps that needed to be replaced, but the oil scraper rings already mentioned above (they have similar functions).
How to check valve stem seals? Some motorists check what exactly is out of order, caps or rings, like this: if smoke comes out of the exhaust pipe for 1-2 minutes, then these are caps, and if it doesn’t disappear completely, then these are rings.
It is not worth neglecting this operation, or postponing it for later. Indeed, behind the failure of small rubber seals there are large malfunctions of larger engine components. internal combustion up to a complete stop of the “heart of the car”.

Oil seals, or, as they are also called - valve seals / valve seals, primarily prevent excess oil from entering the engine. Just like most engine parts, they are made of special rubber and wear out over time and work less efficiently: they separate and allow excess oil to pass through. And this, in turn, leads to an increase in oil consumption. Today we will try to understand not only what valve stem seals are, but also the causes and first signs of their wear.

What are oil seals.

Oil seals are essential in engines to prevent oil and debris from entering the combustion chambers. They are often called valve seals, and this name fully reflects the role they perform.

Valve stem seals are located directly on the valve stems, and consist of three main parts:

• Base;
• Actually cap;
• Spring.

The base is a sleeve made of steel. It plays the role of the frame of this part and gives it the necessary strength. The cap itself is the main element of the part. It is made from a special rubber resistant to high temperatures and friction forces. The cap is mounted inside the sleeve, and when mounted on the valve, fits snugly around the stem and removes oil. And the spring is mounted in a special annular recess of the cap and ensures its tightest fit to the stem.

As for the oil that these caps must remove, it is supplied to the gas distribution mechanism by an oil pump. It is designed to lubricate timing parts that experience friction and increase their resource. At the same time, its penetration into the cylinders through the valve groups is highly undesirable, since, when burned, it forms carbon deposits that accumulate on their walls.

It should be noted that in modern internal combustion engines, valve stem seals have to function in rather harsh conditions of high temperatures and increased mechanical loads. In addition, they are also negatively affected by the substances contained in the removed lubricating fluid. Therefore, manufacturers of valve stem seals use the most durable materials that are resistant to friction, thermal and chemical effects for their manufacture.

The location of the oil scraper caps in the engine

The head with camshafts and valves is mounted on the cylinder block. The valve stem moves through the guide bush. The thermal gap between the leg and the sleeve is closed with caps. The oil seal is positioned so that oil from the head does not enter the combustion chamber. The camshaft journals receive oil under pressure, and the rest of the nodes - due to splashing. Having removed the engine block head and camshafts, you can see the location of the seals in the valve seats.

Wear of valve stem seals

Like any other part of an internal combustion engine, regularly experiencing a whole combination of negative impacts various kinds, valve stem seals gradually but steadily wear out. Their most loaded rubber part loses elasticity over time, cracks appear in it. In addition, over time and under the influence of high temperatures, the clamping force of the spring inevitably weakens. As a result, the wear of the valve stem seals leads to the fact that the oil is not removed from the valve stems and it enters the combustion chamber of the internal combustion engine.

As practice shows, the resource of valve stem seals installed in modern internal combustion engines is approximately 100,000 kilometers. After the car has passed this distance, they must be replaced. Experts also recommend changing valve stem seals in car engines that have been out of service for a long time.

In addition, it often happens that valve stem seals wear out prematurely for one reason or another. In such cases, they, of course, also require replacement with new ones. The fact that the time for this kind of engine repair has come is evidenced by several characteristic signs.

signs of wear

Significantly increased oil consumption; The following signs may indicate wear on the valve stem seals:

• The appearance of soot on the electrodes of spark plugs;
• The appearance of blue exhaust gases at the time of engine warm-up.

The increase in the "oil appetite" of the engine when the valve stem seals are worn is quite logical and understandable. The point is that that lubricating fluid, which is not removed by them from the valve stems, enters the cylinders and burns out. Accordingly, it is irretrievably lost from the lubrication system. power unit, and the oil has to be topped up more often than usual.

As the oil burns, the blue-colored combustion products come out, coloring the exhaust gases in the corresponding color. When the engine warms up, the oil burns almost completely, so the blue smoke disappears.

In addition, if oil, not removed by caps, enters the cylinders, then its smallest drops also settle on the electrodes of the spark plugs. Accordingly, after combustion, carbon deposits form on them.

Consequences of wear of valve stem seals

As soon as the listed signs of wear of the valve stem seals begin to appear, you should check the gas distribution system of the car, and special attention should be paid to the valve stem seals. Experienced motorists do it on their own, less sophisticated ones go to a service station, where experienced specialists perform diagnostics.

It should be noted that it is strongly not recommended to operate the engine with worn valve stem seals. As practice shows, if you ignore this defect and do not eliminate it, then it is almost inevitable:

• The power of the power unit will decrease;
• At idle, it will begin to stall periodically;
• Turnovers will "float";
• Compression will drop significantly;
• Carbon deposits will appear on cylinders, pistons and valve seats.

As for soot, its appearance is indeed a very serious "bell", since its formation may well lead to a very expensive overhaul of the power unit.

HOW TO REPLACE OIL SEALS WITHOUT REMOVING THE CYLINDER HEAD

If the problem with the wear of the valve stem seals was detected in time by the driver, he can replace them without removing the cylinder head. In a situation where the solution to the problem has been delayed, it will be necessary to dismantle the parts in order to remove carbon deposits from the pistons and valves. Depending on the car model and engine, the process for replacing valve stem seals will vary. But there are several main steps that are common to all cars: Before you start replacing the valve stem seals, you need to let the car engine cool down completely; Next, the cover of the gas distribution mechanism is removed; Marks are made on the crankshaft and camshaft, after which the drive is loosened and the camshaft is removed;

The pushing valve springs are dismantled - they are “dry out”; Using pliers or a collet, it is necessary to remove the worn valve stem seal from the valve stem; Lubricate the valve stem and the inner surface of the new caps with oil, having previously removed the spring from them; Install the stuffing box into the frame and put it on the stem, and then press it in until it stops with weak blows; Put the springs on the caps and dry the valves in reverse order. If there is a possibility that the valve stem seals were faulty for a long time, you will need to remove the cylinder head and carry out a full replacement, with cleaning the engine elements from carbon deposits.

Does installing new caps always help?

Of course, replacing caps, especially if you do not remove the engine head, is not a panacea. It happens that the engine, even after replacing the valve stem seals, eats oil. In this case, there is a possibility that a mistake or negligence was made during operation. For example, the stuffing box is not fully pressed or completely torn. But, as a rule, the problem lies in the piston rings. The engine will have to be disassembled (remove the head), take out the pistons and change the piston rings. They change as a whole.

Sometimes it also happens that the car smokes after replacing the valve stem seals. In this case, the reason does not necessarily lie in the rings. Most often, this means that oversights were made during the repair: incorrectly sized caps, inaccurately installed or not replaced at all. If the caps are not fully pressed in, then they will fly off during operation with all the ensuing consequences, so to speak.

In rare cases, when the car smokes and consumes excess oil, decoking of the piston rings can help without replacing the valve stem seals. This procedure will require a special liquid, which is poured into the wells of the spark plugs (after unscrewing the latter).

Before starting the procedure, you need to set all the pistons to approximately the same position. To do this, sticks of the same length are inserted into the candle channels and by rotating the shaft by the nut, they are aligned to one level. After that, the decarbonizer is poured into the holes.

After 4-6 hours, you need to remove the remaining fluid from the cylinders. To do this, the candle channels are covered with a rag and the engine is scrolled several times by the starter. Then the candles are screwed into place and the engine starts. It won't happen right away. It may take several attempts. As it warms up, blue smoke will come out of the exhaust pipe. This is normal and disappears after the engine warms up at idle. As soon as it stops smoking, turn off the engine and immediately change the oil completely. The remains of coke deposits will burn out for another 100-200 km.

Difference between valve stem seals and valve stem rings.

Often inexperienced car owners ask how to determine what is on their car: rings or caps. The answer is that for optimal performance The engine requires the presence of both oil scraper rings and caps. Rings remove oil residue from the moving piston and provide piston lubrication, while valve stem seals are mounted on the valve stems. In fact, both parts perform the same function: they protect the combustion chamber from oil.

The ingress of oil into the combustion chamber of the internal combustion engine is fraught with the appearance of soot on the valve and on the walls of the cylinder of the gas distribution chamber. As a result, the engine will run worse and fail faster. Among other things, the ingress of oil into the combustion chamber degrades the quality of the gasoline-air mixture and clogs the grooves of the piston rings.

What you need to pay attention to when buying valve stem seals:

Of course, it is recommended to use only those caps that are designed for a particular engine, but this is not always possible and advisable. Firstly, new caps on an old motor can be very useful and improve the fit, and secondly, original caps can be expensive or unavailable and it makes sense to order analogues if a replacement is needed here and now.

In order to choose the right cap and it did not jump off and fit in size, you must observe the following selection rules:

1. The analogue can be only 0.5 mm higher than the original. Otherwise, the spring plate may damage the cap.
2. The cap diameter must not be too large, it must pass freely through the valve spring.
Today, domestic manufacturers of caps are inferior to imported ones.

To avoid buying low-quality or counterfeit products, purchase valve stem seals and other spare parts in our online store. We guarantee the correct selection of spare parts and provide a replacement part or refund in case of marriage or incorrect selection.