A crack in the cylinder head occurs as a result of improper engine operation due to overheating and shear stress in the metal.
Symptoms of a crack in the cylinder head
Cracks can appear in different places, hence the different consequences. Basically, there is an opinion that when a head is pierced, white smoke comes out of the exhaust pipe, but this is only one particular case. A crack in the head can occur between different channels, respectively, and the signs of a crack in the cylinder head will be different.
Oil system- when mixing oil and antifreeze in the engine, instead of oil, an emulsion appears, a whitish foam, like a biscuit dough, and an oil film forms in the expansion tank of the cooling system.
inlet- if coolant starts to get into it, then first of all it will wash the pistons to a shine, you can look through the candle hole - the pistons will be like new. And when it enters the combustion chamber, this is just the case when white smoke can go out of the exhaust pipe, although it is not a fact that it will go.
With release channel- here the coolant will simply fly out into the pipe in the form of steam. The engine constantly releases steam and it is unlikely that anything will be noticed in this case, the liquid will simply leave the tank. Most likely, even the smell of exhaust gases in the tank will not.
with combustion chamber- through the crack, part of the liquid will go into the combustion chamber, but a very small amount, all because of the pressure difference. In the engine, when the fuel is burned, a lot of pressure is formed, and the exhaust gases through this very crack enter the cooling system, increasing the pressure in it. Because of this, the nozzles swell, and the exhaust stinks from the tank. But the liquid can also go into the combustion chamber - the cooling system is still under pressure, and the vacuum has already gone in the combustion chamber and air has begun to be sucked in. Due to the difference in pressure, the coolant begins to seep into the combustion chamber. A sign of such a crack will be clean pistons (not always), the smell in the tank, elastic pipes and a cold stove radiator (air lock).
Typical locations for cracks in the cylinder head
Car manufacturers allow cracks to form in the head, and this will not be considered a malfunction, since the crack will not be deep and will not connect the two containers. In VW diesel engines, a head with a crack between the valves is acceptable.
But finding all the cracks is a problematic task even for an experienced minder. It would seem that on the same motors, cracks should form in the same places. But that doesn't make the search any easier. There are places that can be detected with one glance at the head:
—between valves- the crack is immediately visible, passes under the saddles of two adjacent valves.
—between spark plug and valve- the same situation, again, everything is in sight and you don’t have to look anywhere
—in diesel engine crack can go from the valve towards the prechamber, such a crack is easy to see, but how to see it if it forms under the prechamber and does not go outside? 
—under the valve guide- another hot spot where the crack is not visible, firstly, it is already dark in the channel, and secondly, the crack is covered with a guide bushing. Here we need a different approach, and not just a visual one. And what is the use of finding a crack between the valves, if gases do not break through it? We will not rely on chance, especially since the diagnostic method was invented a long time ago and has proven itself from the best side.
Checking the cylinder head for cracks
To check the cylinder head for cracks, it must be pressure tested, that is, all openings must be hermetically sealed and air must be blown into the channels. If you lower the head into the water, then bubbles will come out of the crack. Or vice versa - plug all the holes and pour water into the channel, then pump air into it with a pump, creating a pressure of 0.6-0.7 MPa, and let the head stand for 1 = 2 hours. If the water comes out, then the head is broken.
There are also dyes that tint water. They are very clearly visible on the crack.
And the holes in the cooling jacket are very easy to close: a rubber gasket is placed on the nickname, which is slightly larger than the hole, a metal plate is placed on top, which is screwed to the head with a bolt. And no water will pass. And to the fitting, which will protrude from the head, connect the pump and pump air. Such crimping allows you to identify all cracks.
Crack repair
Qualitatively repair the crack can only be done by welding. No adhesive composition will be able to qualitatively close a crack in the heads, because when heated to operating temperatures, the head will expand and the crack will become larger, that is, a composition is needed to close the crack, which would have the same linear thermal expansions as the head material, to also be resistant to other loads. All this can only be achieved by welding.
Preparing the Welding Head
Before welding, the crack must be cut; for this, metal is drilled along the entire length of the crack with a milling machine. The groove should turn out to be deep enough, 6-8 mm deep and approximately the same in width, it is desirable to make a wedge-shaped shape. This will help to weld the metal better. To cut a crack between saddles, you first need, and only then cut the crack.
After cutting cracks, the head must be heated to a temperature of 200-250 ° C, but not higher, so that the head does not lead. Heating allows you to reduce the stress in the metal that occurs during welding. For heating, it is best to use an acetylene torch or oven, but you can not use a blowtorch, because it can easily overheat the cylinder head.
Cylinder head welding
Gas welding with filler material can be used to weld the cylinder head, but argon arc welding (TIG) gives better results. A mass is connected to the head, and the arc burns in an argon environment between the tungsten electrode and the head, where an aluminum filler wire is slipped.
After welding, the seam must be cleaned, re-pressurized, and if everything is fine, then the surface adjacent to the block must be milled so that it is perfectly even.
To perform the work, you will need a special template or a wide locksmith's ruler.
Execution sequence
1. Remove the cylinder head (see " Cylinder head - removal, gasket replacement and installation").
2. We clean the head of the block and the covers of the camshaft bearings from dirt and carbon deposits, wash it from oil deposits, remove carbon deposits from the walls of the combustion chambers with a metal brush.
3. We carefully inspect the head of the block and the covers of the camshaft bearings. They should not have cracks. On the working surfaces of the camshaft bearings and on their covers, there should be no scoring and traces of metal enveloping. The guides and valve seats must fit snugly in the body of the head, with no traces of their displacement during timing operation. Valves and their seats must not have cracks or burn marks.
4. We check the flatness of the cylinder head with a special template.
Check the lower mating plane of the cylinder head, if there is no template, with a sufficient degree of accuracy, you can use a wide locksmith's ruler. The ruler is applied with an edge to the plane of the head diagonally. Make sure that there is no gap between the edge of the ruler and the plane of the head. The gap can be observed both in the middle part of the plane and along its edges. Measure the gap with a set of flat feeler gauges on both diagonals.
The maximum allowable gap is 0.1 mm.
If the gap is greater than the allowable, the head is subject to milling of the mating plane or replacement.
The cylinder head should only be replaced in conjunction with the camshaft bearing caps.
5. We check the tightness of the cylinder head: for this, on the end surface of the head, we muffle the window for supplying coolant to the thermostat (you can install the thermostat pipe by placing a gasket cut out of sheet rubber under it). We turn the head over and fill with kerosene its internal cavities (through which coolant circulates). We are convinced that there is no leakage of kerosene from the cylinder head.
In the event of a leak, as well as when shells are found on the mating plane, you can try to repair the block head using a “cold welding” repair compound or replace it.
6. To check the tightness of the valves of the block head, lay it on a horizontal surface with the mating plane up.
7. We fill the combustion chambers of the block head with kerosene. If the level of kerosene in any chamber drops, then one or more valves are leaking. 
An experienced motorist knows that the operation of the car depends on the performance of the engine. And one of the main components of the motor is the head. How to check the cylinder head for microcracks and what are the signs of cracking on the head? You can learn more about this here.
Signs of cracks in the cylinder head
In most cases, motor wear occurs in its upper part, that is, on the head. There are many reasons that affect the failure of the block. The most common is overheating of the motor when antifreeze completely flows out of the cooling system. This occurs as a result of incorrect tightening of the cylinder head pins. This and the incorrect operation of the temperature control device can cause deformation of the cylinder head plane.
The arrow marks the surface defect
Consider the signs and symptoms that indicate the appearance of cracks in the cylinder head and the need to repair the unit:
- The motor fluid foams, bubbles appear in it. If a crack has formed in the head, coolant may enter the oil. In this case, the antifreeze will leave the expansion tank for an unknown reason. If you need to constantly add refrigerant to the system, this should alert the owner of the car. In this case, an oil film will form in the antifreeze expansion tank - this is an exact symptom of the appearance of a microcrack in the engine head.
With such a malfunction in warm weather, the temperature of the motor will either fall or rise. This sign is not common, but if you notice that the arrow on the temperature sensor either drops or rises again, then this should alert you.
Defect on cylinder head
If coolant gets into the intake valve, then during a long ride it will literally wash the pistons to perfect cleanliness. This is easy to check: unscrew the candles and look at the condition of the pistons.
Options for diagnosing the problem
To make repairs and eliminate microcracks, you need to be completely sure that they are. Consider several diagnostic options that can be done at home.
Magnetic particle diagnostics
The method is the most efficient type of repair in the detection of microcracks. It consists in the following: install magnets on all sides of the cylinder head. Sprinkle the cylinder head with metal shavings on top, it will begin to move towards the magnets, remaining on cracks and dents. So, it is not difficult to notice cracks.
Metal shavings for diagnostics
Fluid diagnostics
To check the cylinder head for defects by this method, you will need a special coloring liquid.
- Rinse the surface of the head thoroughly, for this use acetone, kerosene or another type of solvent.
- Apply a special liquid to the cleaned surface and wait a few minutes.
- Then rinse off any remaining liquid with a clean cloth. If there are defects on the cylinder head, they will be visible to the naked eye.
Pressure test
The method can be implemented in several ways: with and without immersion of the cylinder head under water. Do a immersion test:
- If you decide to make diagnostics by immersing the cylinder head in water, then you need to tightly close all the channels of the circuit of the upper part of the unit, then place it in a container and pour hot water into it.
- Then apply compressed air to the cylinder head circuit and where bubbles appear, there will be microcracks.
Pressure Diagnostic Equipment The method without immersing the block in water is carried out to search for holes in punctured tires:
- it is necessary to firmly close all the channels of the cylinder head circuit.
- After that, a soapy solution should be poured onto the surface of the head cover.
- Air must be supplied to the circuit. Where a defect is found on the surface of the head, soap bubbles will appear.
Water test
The method does not differ from the previous one. The only difference is that the head does not need to be lowered into the water, but water should be poured into it:
- Close all openings tightly.
- Pour more water into the channel.
- Then, using a conventional pump, you need to pump air into the channel to make the pressure at least 0.7 MPa.
- After that, you need to let the head stand for several hours. If the water is gone, this indicates head defects. So no repairs are needed.
Argon surface welding Defect repair
It is desirable to repair block cracks by welding, this method is the most effective and reliable.
- Before starting the repair, you need to cut out a piece of metal that corresponds in size to the crack. The groove depth must be at least 8 mm, and the shape must be wedge-shaped.
- Before brewing the head, it must be heated to a temperature of 200 degrees. To do this, you can use an acetylene torch, but not a soldering iron.
Head Crack Welding
Video "Repair of microcracks"
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A crack in the head of an engine block is a serious problem that can be fixed at best with an expensive repair, and at worst with a major overhaul or replacement of the motor. Basically, cracks in the head appear as a result of overheating, freezing of the coolant, or after third-party mechanical impact.
The first signs of a crack in the head:
Reducing the liquid level in the expansion tank;
Oil traces on the surface of the coolant in the tank;
Bubbles in the expansion tank;
Problems with the temperature of the coolant (critical heating or vice versa).
Diagnosing such a malfunction is very simple, all the signs lie “on the surface”, but finding the crack itself is extremely difficult, and sometimes completely impossible. Sometimes even experienced mechanics can fiddle with an engine for many hours before finding a crack.
1. In the gaps between the valves. Such a crack is visible to the naked eye, it clearly passes between the seats of adjacent valves.
2. Between spark plug and valve. A similar situation - the crack is clearly visible and there is no need to look for it.
3. From the location of the valve to the prechamber (on diesel engines). This crack is also visible.
4. Crack under the prechamber. It is very difficult to notice such a defect, and sometimes even impossible.
5. Directly below the valve guides. An unpleasant defect is rare and imperceptible. Firstly, such a crack is covered by the valve guide, and secondly, it is always dark in the channel and it is very difficult to illuminate there.
1. Electric or gas welding. Eliminating a crack using this method is similar to eliminating defects on a cast-iron block of a VAZ engine. To begin with, holes are drilled along the edges of the crack, then the crack itself is slightly deepened and expanded. This is done for improved adhesion of the weld to the metal of the block head. Also, you first need to warm up the block head itself to a temperature (600 - 700C). Next, using a copper-cast iron filler material and flux, a neat seam is applied to the defect site. Note that the welding seam should rise above the surface of the head by about 1 - 1.5 millimeters. After completion of welding work, the head of the block should cool down slowly in a thermal cabinet. In some cases, welding is carried out without preheating, but then it is better to use direct current electric welding. Another option is to install a patch in place of the crack. For such repairs, it is better to use electric welding with copper electrodes wrapped in tin. After performing such work, the welding seam must be cleaned and coated with epoxy paste.
2. Use of epoxy resin. The crack and the surface in its immediate vicinity are carefully cleaned, preferably to a shine. Further, again, holes are drilled along the edges of the crack (diameter 3 - 5 mm.). Threads are cut into them and aluminum or copper plugs are screwed in (flush). After that, the crack itself must be processed to a depth of ¾ of the wall thickness and at an angle of 70 - 90 degrees. Notches are necessarily applied to the surface of the crack, this is done to give it a certain roughness. After that, it remains to qualitatively degrease the entire surface and apply a layer of epoxy paste. The paste (resin) itself must be applied with a spatula in about three layers. The thickness of each applied layer is 2 mm. Hardening of the applied layers occurs during the day. If the surface of the head is subjected to intensive drying or heating, then the resin will harden in three to four hours. At the end, the applied layer of epoxy must be sanded with a grinder or a regular file.
3. Epoxy resin (paste) and fiberglass. The preparatory work of this method is similar to the previous paragraph. Yes, and the principle of applying the paste is also similar, but in this case, after applying each layer of resin, a patch of fiberglass is installed, which must be rolled with a roller. It should be borne in mind that there should be at least 20 millimeters from the edge of the patch to the extreme point of the crack. In total, you can apply from two to eight such layers. The final layer is necessarily covered with resin and cleaned with a grinder or a standard flat file.
4. Use of pins. Holes with a diameter of 4 - 5 millimeters are drilled at the edges of the crack. Further, more holes are drilled throughout the crack, the step between them should be within 7 - 8 millimeters. All holes are threaded. Next, copper rods are screwed into the prepared holes, the tops of which must be cut, but not completely, but so that the tips remain on top at a height of 1.5 - 2 mm. The next step is to drill new holes along the crack so that they necessarily overlap the existing holes. As a result, you should get a continuous strip of bars. The last step is to pound out the copper tops of the rods with a hammer, this way you form a solid copper seam. For greater reliability, the finished seam is coated with epoxy.
After completing all the work, the head must be pressed. Note that all work must be carried out by professionals or people who know how to handle materials and tools, and also understand the complexity and seriousness of such repair work.
A microcrack in the cylinder is probably the biggest headache, the owner of the car, and the master to whom he refers. The thing is that you can’t see it visually, but the symptoms are that the gasket under the head begins to burn out. Several times I came across such engines. But there is also a microcrack in the head. The sign of a microcrack in the cylinder and head is the same as the beginning burnout of the gasket under the head.
I'll tell you first about the microcrack in the head, and below about the microcrack in the cylinder.
A guy drove up in a VAZ-2106 and said the car was boiling all the time, waited for a while until the engine stopped boiling, opened the radiator cap and added coolant to the radiator, started the engine at idle. I began to look into the radiator, I see bubbles coming out of the radiator (but if you add liquid to the radiator, then usually several bubbles pop up at once, but they quickly stop), in front-wheel drive cars it starts to inflate the tank into which coolant is poured and bubbles also go. If the head gasket burns out badly, then the liquid goes into the cylinder, through the piston the liquid seeps into the engine block and enters the oil, a sign that the oil becomes the color of a white emulsion and increases in volume.
I immediately determined that the gasket was starting to burn out, I removed the head and the gasket was new (completely fresh) and there was no hint of burnout, I asked if they had already changed the gasket, he says I bought the head from my hands two days ago, replaced it and has been boiling since then. I ask, but before that it was boiling on the old head, she says, it didn’t boil, but it was troiling due to valve burnout, I decided to buy this head, and they offered it not too expensive, so that it wouldn’t suffer with it. I say you have two options, buy another head, or bring the old one, I will fix it, he decided to repair the old one (the head was really badly stubborn, I had to change all the valves and valve guides). Put the repaired head and boiling stopped. But what's funny, after a while, another guy drove up to me in a VAZ-2107 and also complained that the engine was boiling, opened the hood and recognized the head because of which the six was boiling (it had a stain of red paint, that's why I remembered it). I asked him for a long time he changed the head, he says, the other day. I told him the story of this head. Visually, I did not find microcracks in this head, and I did not understand in what place it was.
Photo. Micro crack in the head
Most often, a microcrack in the head happens as shown in the photo, and most often in my practice it happens in the second or third cylinder. The red photo shows the location of the microcrack. It is easier to find a microcrack this way, clean the soot with a knife in the place where the crack is shown, and it appears.
Photo. Head from Niva with two microcracks at once
And once I came across a head with two microcracks at once, it is in the photo and the cracks are shown by arrows, I found them right away, it was only necessary to remove carbon deposits with a knife. The sign of these microcracks in this Niva was such that the second and third cylinders troiled, at low speeds, the antifreeze left and flew out through the muffler, bubbles also went into the radiator, but the antifreeze did not go into the oil. Maybe because this engine has a very good piston group, but if there was a bad piston group, antifreeze would penetrate into the block. It remained a mystery why the antifreeze did not penetrate into the oil through the pistons, I think it entered the cylinders very little, mainly the pressure forced air into the head and completely sucked drops into the cylinders.
Signs such as a microcrack in the head will not be repeated, but I will immediately be taken aback by the method of repairing such a cylinder. Well, if you can visually find such a crack, it may be a chip in the cylinder, but more often you can’t see it, but it appears when the engine is running and heated to operating temperature. I encountered a microcrack when the engine was running for a long time, and suddenly a microcrack appeared, but where it is is unknown.
Photo. The crack in the cylinder is marked with an arrow.
In the photo you see a VAZ 2106 engine block with a crack in the cylinder. And all because this block is designed for 79mm pistons, it was bored out for 82mm pistons. and it looks like they ran in badly, which led to this crack, the signs were such that there were constant bubbles in the expansion tank.
I came across several cars with a VAZ 2106 block bore for 82mm pistons. and generally worked fine. But I do not advise you to do this, since the cylinder liner becomes very thin, and there is a high possibility of such a crack forming.
Photo. A head with three cracks, please note that this head was milled on a machine, but such milling is unacceptable, since very deep irregularities remain, they are immediately pressed through by the metal part of the gasket, which contributes to the rapid burning of the gasket. The milling head must be absolutely smooth.
I had to sleeve this block, and put 79mm pistons. the engine ran like new.
I always warn the owner of the car after I remove the head and do not find burnout in the gasket and cracks in the head or block, which can be two reasons, and I give him a choice where to start first, replace the head or we will sleeve the block.
The main thing is that the borer that bores the cylinders and liners the block is a professional in his field. A good borer can perfectly line even an obvious crack in the cylinder. Therefore, immediately warn the borer that there is a microcrack in some cylinder (I don’t know the subtleties of how the cylinders are lined), but several of these engine blocks have been running for several years after the sleeve and everything is fine.
Usually the owner of the car chooses to start with the sleeve of the block, and if it doesn’t help, then of course you will have to change the head.
I know one ninety-ninth, which drives with such a microcrack, the driver simply twists the cork slightly on the expansion tank so that it does not inflate, and it does not boil.
It happens like this, the engine is started, it works normally, but after a while coolant starts to flow from under the plug of the expansion tank. You might think that the reason is a microcrack in the gasket, head, or engine cylinder, but there are no bubbles in the expansion tank during warm-up. Usually the plug of the expansion tank is to blame for this, the valve does not hold pressure in it, as soon as it is replaced with a new one, everything stops.
Interestingly, I saw cars that even drove without plugs in the expansion tank, but did not boil, while others begin to boil and form air jams due to a bad valve in the expansion tank cap. This is a mystery to me.
The defects that appear most quickly on the cylinder head are the smallest cracks. Their appearance does not have the best effect on the operation of the cylinder block, and therefore the engine as a whole. What signs indicate the appearance of damage to the head, how to check the cylinder head - we will find out in this article.
The signs of the appearance of microcracks on the BC head are as follows:
- Vibration or so-called engine tripping when the car is driving uphill. This phenomenon may be due to the appearance of microcracks. If coolant enters the cylinder block, then it will certainly be on the spark plugs. Just unscrew one of the candles, if its electrode is wet - taste the liquid. If it is antifreeze or antifreeze, then the taste will be slightly sweet, and this will indicate that the antifreeze enters the cylinder block through microcracks in its head.
- Foaming engine oil should also lead to suspicion of microcracks in order to check the cylinder head. Engine oil foams due to the ingress of antifreeze (antifreeze) into it. At the same time, the coolant level in the tank is constantly decreasing, and requires replenishment to a normal level, and an oil film forms on the surface of the antifreeze in the tank. The engine also reacts to this, in warm weather - either by a drop in temperature, or by its increase.
- Antifreeze boils. To state a malfunction of the cylinder head, you need to open the expansion tank, add the required amount of antifreeze and start the engine. If the coolant boils almost immediately, then the cylinder head is not working.
- Engine oil runs out too quickly. If a crack on the head of the BC has formed near the intake valve, then, with the engine running, the oil will constantly be drawn into the cylinder. If not oil, but antifreeze, is drawn through the inlet valve, then the cylinder pistons will become perfectly clean - you can check this by unscrewing the spark plugs.
How to check the cylinder head
There are several ways to check. Watch the video below.
Checking with magnets and metal chips
This is the fastest and easiest way to check the cylinder head. Magnets are installed along the entire plane of the head, and the head itself is sprinkled with metal shavings. The chips begin to move towards the magnets, getting stuck in cracks, small depressions and thus making them obvious to the eye.
Checking with a special liquid
- Rinse the head plane with any solvent.
- Apply a special liquid to the washed surface and let it stand for several minutes.
- As soon as you remove, with a dry cloth, the remaining liquid, the defects present on the head will appear.
Pressure test
Pressure can be used to check the cylinder head by immersing it under water or without immersing it.
Submerging under water:
- Before immersion in water, you need to close all the channels of the head. Then put the cylinder head in a container and fill it with hot water.
- Apply compressed air to the head circuit. If there are tiny cracks somewhere, then bubbles will appear in this place.
Not immersed in water:
- In the same way as in the first case, close the channels of the head contour.
- Prepare a soapy solution and then pour it onto the head cover.
- Supply compressed air to the circuit. Microcracks in the cylinder head can be detected by soap bubbles.
Water test
To check the cylinder head, you will need to fill it with water.
- Close all openings of the head tightly.
- Pour a large amount of water into the channel.
- Raise the pressure in the channel to 0.7 MPa by pumping air into it.
- Leave the cylinder head for a few hours. If, after this time, the water leaves the head completely, then there are cracks in the part.
Video: How to check the cylinder head for microcracks
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Repair of the cylinder head, as you understand, is a long tedious work that requires special care. If you think that this is like pissing two fingers, you are greatly mistaken. I'll tell you why. First you need to remove the head, on some cars it is easier to remove the entire engine than to remove only the head. The removed head must be thoroughly washed with diesel fuel or better with gasoline, and it would be very good to put it in a bath with caustic soda.
Further visual inspection and diagnostics. Aluminum heads have such a feature or property - after overheating, the plane of the cylinder head is slightly curved, after which the cylinder head gasket (cylinder head) begins to pass oil and water in small or large quantities. Oil and coolant can seep both outside (as a result, the engine becomes dirty and shows that it needs repair with all its appearance), and inside the engine, where the coolant will enter the sump and mix with engine oil, turning into engine poison, which staggers the engine of your car very quickly.
It is necessary to check the plane, for this I have a special ruler, ideally flat, made at the factory of ultra-precise instruments specifically for measuring the unevenness of flat surfaces. How can a person who does not have such a device measure the plane of the cylinder head, I don’t even know ... But if you still find something suitable with a perfectly flat surface, then do the following: 1. Clean the plane of the head from soot, scale and remnants of the old cylinder head gasket. 2. On the cleaned plane of the cylinder head, place your "measuring device" along the length of the head and look at the gap between the device and the plane of the cylinder head, move the device along the entire plane, set it diagonally and look for the gap again. If there is no gap, then the cylinder head plane is in order; if there is a gap of 0.5-1mm, then it is better to trim the head or, if finances allow, to put in a new one. if the gap is more than 2mm, then the head needs to be restored, that is, it is necessary to trim. When facing the cylinder head, the curved layer of the plane is removed, after which the cylinder head can be used again. P.S. A driver who checks the oil in the engine at least once a week, seeing that the oil has doubled, and the radiator is half empty, simply pours more antifreeze into the radiator and drives on, in a few days he will get to repair and spare parts.
yamotorist.ru
How to check the cylinder head on a vaz 2114 - Repair 2114
To perform the work on checking the cylinder head, you will need:
- flat feeler set
- special template or wide locksmith's ruler
Related video:
Remont2114.ru
Checking the cylinder head
Remove all deposits from the walls of the combustion chambers (Fig. 2.121). Check the cylinder head for cracks in the intake and exhaust ports, combustion chambers and on the surface of the head. Using a straightedge and a feeler gauge, check the flatness of the cylinder head-to-cylinder block interface at a total of 6 locations. If the deformation exceeds the limit, correct the sealing surface with the plate and about #400 sandpaper (Waterproof Silicon Carbide Sandpaper): Wrap the plate with sandpaper and sand the sealing surface to remove the raised spots. If after this the measurement results are not correct (exceed the limit value), replace the cylinder head. Leakage of combustion products through the plane of the head and cylinder block is often the result of deformation of the sealing surfaces: such a leak leads to a decrease in engine power (Fig. 2.122). Limit value of deviation of the sealing surface of the cylinder head from the plane: 0.03 mm. Deformation of the mounting surfaces of the manifolds: Check the mounting surfaces of the manifolds on the cylinder head using a straight edge and feeler gauge to determine if it is possible to edit the surfaces or if the cylinder head needs to be replaced (Fig. 2.123). The limit value of the deformation of the seating surfaces of the intake and exhaust manifolds on the cylinder head: 0.05 mm.carmanz.com
How to check the cylinder head after grinding?
Checking the cylinder head, in principle, is not so difficult.
Clean the cylinder head from dirt, oil, chips. Carefully inspect the head from all sides to ensure that there are no shells and cracks.
In specialized workshops, the plane of the block head is checked with a special template.
At home, when this template is not available, you can check the flatness with a metal wide long ruler. It must be applied to the plane of the head with an edge, the figure shows in which places to apply
And check the gaps with a feeler gauge. The gap is checked around the entire perimeter. Ideally, there should be no gaps. But if the gap is not more than 0.01 mm, then this is allowed.
I emphasize and highlight: a new or polished cylinder head, the gap is NOT MORE THAN 0.01 mm.
Because with gaps of 0.1 mm left (in some repair instructions, this particular typo was made), there will be a high probability of breaking through the head gasket. And this is again the analysis and repair of the cylinder head, and even the entire engine, up to its replacement.
The cylinder head must also be checked for leaks. This can be done, for example, by pouring kerosene into the cooling cavity by plugging the liquid supply hole. Crimping is also done with compressed air of about 1.5 - 2 atmospheres, but this, of course, requires a compressor, a bath, that is, certain conditions.
When the head is checked, ground, and again checked for flatness, for tightness, then you can install the valves, after lapping them in, and after assembly, also check them for leakage with kerosene. If the kerosene does not flow for about half an hour, then this is a good sign that the valves are lapped.
The cylinder block, of course, also do not forget to clean it from soot, rinse it from dirt, clean and blow through all the channels. Wash the crankcase, the oil pump receiving grid, make sure that the oil pump itself is working. Well, you can proceed to the final assembly of the motor.
