DIY diesel cylinder head repair

In detail: DIY repair of a diesel engine cylinder head from a real master for the site my.housecope.com.

Head repair begins with thorough cleaning with kerosene or solvent. We remove carbon deposits from the combustion chamber and from the valve plates with a metal brush, clamped in the chuck of an electric drill. When disassembling the valve mechanism, you will need a valve desiccant, for example, the one shown in the photo below, but the most effective one is easy to make with your own hands, according to the drawings published here in this article.

Before and after disassembly, we carefully inspect the cylinder head. Cracks, chips in any places of the head are not allowed. If you suspect that coolant has entered the oil, we check the head for leaks, for this it is necessary to plug the holes of the cooling jacket and lower the head into warm water, inject compressed air into it under a pressure of 1.5 - 2.0 kg. No air bubbles should be emitted within 1.5 minutes. In more detail about such a check, as well as about the repair of a cracked head, I wrote here.

Saddles valves. The shape of the valve seat chamfers is shown in the photo. On the working chamfers of the seats in the contact area with the valves, there should be no corrosion, pinholes, burnouts and damage. We eliminate minor damage by removing (as little metal as possible) with a special set of cutters with guides (for example, a high-quality set of the American company NEWWAY). I wrote about this in detail in this article.

After that, thoroughly rinse the head, seats and oil channels and then blow them with compressed air.

Valve guides... We check the gap between the guide bushings and the valve stems, respectively, by measuring the valve stem with a micrometer and an inner gauge for the guide sleeve hole. Clearance for new bushings: 0.022 - 0.055 mm for intake valves and 0.029 - 0.062 mm for exhaust valves. When worn, the maximum allowable clearance is 0.3 (in the absence of increased noise). If the increased clearance between the guide and the valve cannot be eliminated by replacing it with a thicker valve, then we change the guide sleeve (press out) - read about it here.

Video (click to play).

It is possible to increase the diameter of the valve stem with chromium plating, provided that there is no step (uneven wear of the diameter) on the stem. If new bushings have been pressed in (it is better to order bronze bushings for a turner), then after pressing in, they must be deployed with a special reamer with a long guide. Then we rub the valves to the seats with lapping paste (preferably water-based) - read how to do this correctly here.

Also, we check the valves with a dial indicator for the absence of curvature of the rod, scrolling the valve in two small prisms and watching the deviations of the indicator arrow. A deviation of even a few hundredths of a mm. unacceptable. The valve stem seals are naturally replaced with new ones.

Valve springs we inspect for cracks, check the elasticity.

Pushers valves: we check their working (rubbing) surface, it should not be scored or scratched.

Camshaft , the working surfaces of the cams, the surfaces for the oil seal, as well as the eccentric (not at all) are bleached or cemented to increase wear resistance, these surfaces must be polished and not have any marks, scratches and wear in the form of abrasions, steps.

If there are deep risks and the above listed defects, then the shaft must be replaced. We install the camshaft on two prisms and check the radial runout using the indicator rack.The runout of the bearing journals and the rear of the cams should not exceed 0.02 mm. Well, I advise you to read how to increase the resource of a standard camshaft here.

Bearing housings the camshaft must not have cracks and damage, and there must be no scoring or scratches on the bearing surfaces for the camshaft journals. The gap between the camshaft journals and the support holes is determined by measuring these parts and deducting a smaller one from the larger one (micrometer and internal gauge).

Also, the gap can be determined using a plastic calibrated wire (described using the example of a crankshaft) Design gap for new parts: 0.069 - 0.11 mm, and the maximum allowable wear: no more than 0.2 mm. After replacing parts that do not fit into the maximum allowable clearances, it remains to assemble everything. After milling the seats and grinding the valves on the valve at the point of contact with the seat, there should be a thin (1 - 1.2 mm) matte strip, without breaks in a circle.

After assembling the valve mechanism (drying out), we check the valves for leaks, for this we fill the combustion chambers with kerosene, for at least two minutes, or better than five, there should be no leakage of kerosene between the saddles and the valves. Next, we install the head on the block, naturally, installing a new gasket between them.

The order of tightening the head bolts and nuts of the bearing housings, see the photo below. When tightening, we use a torque wrench, and the required tightening torque for the bolts is found in the manual of our engine. It remains to put on and tighten the drive pulley and adjust the thermal clearances.

valve dehydrator

Adjustment of thermal gaps.

The thermal clearances of the valves on each engine model have a different meaning, on diesel engines it is more, on gasoline engines it is less, and each manufacturer writes its own value in the manual or on the sticker of the valve cover (for exhaust, it is always more, since the heating is more).

I will describe the adjustment of the gaps and, if there are any numbers, then this is just an approximate value. In general, there are two main methods of adjustment: by replacing the adjusting washers (on newer motors), and on older (classic) motors, using adjusting bolts with locknuts.

Shim method: to begin with, we set the camshaft according to the marks (usually on the pulley and the head connector with the block), but turn the crankshaft bolt only clockwise and then turn it another 40 -50 °. These are 2 - 3 teeth on the camshaft pulley, while there will be a combustion phase in the first cylinder.

We measure the valve clearances of the first cylinder using a feeler gauge and if the clearances are more than normal, then we remember how much more, then we squeeze the pusher and remove the adjusting washer. We measure its thickness with a micrometer. Determine the thickness of the new washer using the formula: T = B + (A - B), where T is the thickness of the new washer, A is the measured gap, B is the thickness of the removed washer, B is the nominal gap mm.

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For example: A = 0.28 mm; B = 3.80 mm; B = 0.25 mm, then we get T = 3.80 + (0.28 - 0.25) = 3.83 mm - the thickness of the new washer. Pulling the pusher (with a special mandrel), install a thicker new washer, then check that the dipstick should enter between the pusher and the cam with slight pinching. It remains to consistently rotate the crankshaft half a turn (and the mark on the camshaft pulley is rotated by 90 °) and adjust the clearances on the valves of the remaining cylinders.

Method with adjusting bolts even easier. First, in the same way, we set the camshaft on the marks, which corresponds to the end of the compression stroke of the piston of the first cylinder, check the gap size at both valves with a probe, and if the probe passes freely or does not pass at all, we make an adjustment.

To do this, put a spanner wrench on the adjusting bolt, and loosen this lock nut on the open-end locknut.Then we insert a dipstick between the adjusting bolt and the valve stem and turn the bolt, making sure that the dipstick slides with light effort, when we have achieved it, remove the dipstick and tighten the lock nut, making sure that the adjusting bolt remains in place (does not turn).

Similarly, we adjust the clearances in 3, then 4 and 2 cylinders, turning the crankshaft 180 ° after each cylinder (the camshaft will rotate 90 °, respectively). That's all, close the valve cover.

You can read more about adjusting valve thermal clearances here.

Valve clearance adjustment.
1 - valve stem, 2 - dipstick, 3 - rocker arm, 4 - camshaft cam, 5 - box wrench, 6 - hex key, 7 - adjusting screw, 8 - lock nut.

Often on engines that have been operated with incorrect thermal clearances, the valve discs in the place of their contact with the seats burn and lose their tightness. From this, the compression in the cylinders naturally falls, and, accordingly, the engine power decreases.

You can restore the motor to its former strength by rubbing the valves. How and with the help of what to do this correctly, you can read here in this useful article. Well, about the device, maintenance and repair of the engine head, I wrote a separate detailed article here.

I hope this article on cylinder head repair will be useful to novice craftsmen, success to everyone.

Let's start by defining the concepts. The cylinder block of a modern car is the basis of the engine, on which the rest of the engine components are installed: cylinders, crankshaft, oil pan, cylinder head.

It is precisely the malfunctions and repairs of the cylinder head that we are interested in. Is it possible to repair the cylinder head with your own hands in a garage-home? And craftsmen answer unequivocally - yes, repairing the cylinder head with your own hands is possible.

Let's start by clarifying that repairing a cylinder head is a complicated operation and will require from you: a little bit of understanding of the block device, the presence of a special locksmith tool and the ability to own it.

Basic tools required for cylinder head repair

Mandrel for pressing in valve stem seals.
Micrometer for measuring valves and guide sleeves.
Reamer for unrolling new bushings.
Mandrel for pressing out bushings.
Mandrel for pressing in bushings.
Devices for drying valve springs.
Set of countersinks for the restoration of valve seats.
Electric hotplate for heating the cylinder head during troubleshooting and before pressing the bushings.

Do not forget about the necessary spare parts and tags

As a rule, almost any repair of a cylinder head requires its dismantling. Exceptions are, for example, replacement of valve stem seals. Therefore, before starting to dismantle the cylinder head, think about purchasing the necessary set of spare parts.

Today's market provides Head Sets (or, in simple terms, upper sets), which include a cylinder head gasket and all the oil seals and gaskets located above the main gasket.

Well, the tool and the minimum kit are ready, we start troubleshooting the cylinder head.

Before dismantling, be sure to check the relative position of the crankshaft and camshaft according to the marks. Up to the point that we put additional marks on our own.

For specific car models, the technology for dismantling the cylinder head is described in the manuals. But the peculiarities of some operations are worth recalling.

We loosen the head mounting bolts from the middle by 0.5-1 turn, alternately. The bolts with internal slots must first be cleaned of carbon deposits, otherwise a loosely inserted key threatens to break off and problems during dismantling;
when dismantling the cylinder head, if there is no connection diagram for all kinds of vacuum tubes, then you need to sketch this diagram yourself, having previously applied the appropriate marks.
When removing the valve springs, use dryers, not the “strong hammer” principle.

Cylinder head condition monitoring

Basically, there are not many basic parameters in the cylinder head that need to be checked before you start repairing the cylinder head. So let's start looking for typical cylinder head malfunctions.

The lower plane of the cylinder head... It is checked using a straight edge and a set of probes. The ruler is placed along the diagonals of the head on a plane and the thickness of the gap is determined using a feeler gauge. If the clearance is more than the maximum allowable clearance of 0.05-0.06 mm, then grinding of the cylinder head is required.

Worn camshaft journal journals and bearings... All diameters are measured with a micrometer and compared with the maximum permissible values for a particular engine model. Based on the measurement results, a decision is made on the type of repair or replacement of parts. Do not forget to visually assess the external condition of the surfaces. They should not have obvious signs of mechanical damage: scratches, chips, scuffs, grooves, etc.

Wear monitoring of valve stems and bushings... It is made with a micrometer at several control points of the rod around the circumference. The valve is changed if the difference in diameter exceeds the maximum permissible parameters specified by the manufacturer.

If you do not have such a device as an internal gauge to determine the wear of the guide bushings, then it can be determined by the valve play (new) in the bushing. As a rule, bushings are replaced with new ones.

Wear of such parts, like: saddles, levers, rocker arms, cams are determined visually. If the chamfer on the valve is "failed", but the rod is in order, then it is processed, and the valve can be reused.

Other cylinder head defects can also be identified visually. The presence of burrs and serifs on the surface of the block head is eliminated by grinding the cylinder head to eliminate the leaky connection between the cylinder head and the block itself.

Thus, we carry out the repair of the cylinder head simultaneously with the troubleshooting, as they say, as soon as troubles arrive.

Good luck with DIY cylinder head repairs.

The cylinder head (cylinder head) is an essential component of any automotive engine. It is in the combustion chambers of the head that the air-fuel mixture is compressed, then the mixture is ignited by the spark of the spark plug, and the working cycle is performed. Image - DIY diesel cylinder head repair

To create the required pressure in the cylinders, the cylinder head must be sealed; for tightness, a gasket is installed between it and the cylinder block. But it should be noted that there are designs of internal combustion engines (ICEs) in which the cylinder head is a single unit with the cylinder block, that is, it is a monolith. An example is the Austrian diesel internal combustion engine Steier, which was installed on GAZ vehicles in the late 90s of the XX century. In such an engine there is no head gasket, which increases the reliability of the connection, but complicates the engine repair.

The cylinder head of passenger cars is made of cast iron or aluminum, but recently cast iron is almost never used - metal has its drawbacks. In any block head, the number of combustion chambers is equal to the number of cylinders in the engine, and if there are 4 cylinders in the internal combustion engine, then there are also 4 combustion chambers in it.

exhaust and intake valves;
guide bushings;
valve springs;
crackers;
valve stem seals;
pushers;
valve seats.

Almost all modern engines have an overhead camshaft, so there is a seat (bed) in the block head for the camshaft. Valves in the cylinder head are needed to fill the cylinders with a fuel-air mixture:

through the intake valves, the mixture enters the cylinder;
exhaust gases are discharged from the engine via exhaust valves.

The valves are raised and lowered using the camshaft cams and run along the guides pressed into the cylinder head.The clearance between the cams and valves is adjusted using pushers, which in turn can be hydraulic or mechanical.

The valve stem seals are needed to seal the connection, they prevent oil from entering the combustion chamber. There are seats under the valve discs, and when the valve is closed, the seat is used to seal the combustion chamber.

Modern passenger car engines can have two or four valves per cylinder, and if the internal combustion engine has 4 cylinders, such motors are called 8 or 16 valves.

Automotive engines tend to break down; ICE failure can occur for various reasons. Including various malfunctions occur in the cylinder head, the reason may be:

burnt out valve;
deformation of the cylinder head surface due to overheating;
the appearance of cracks in the head;
wear of the guide bushings;
seat wear.

You can repair the cylinder head yourself - here a lot depends on the skills of the repairman and on the complexity of the engine itself. The least difficulty is the repair of an 8-valve block head, the simplest thing here is replacing the valve stem seals, except for adjusting the valves. On many car models, replacement of the caps can be done without removing the cylinder head, depending on the complexity of the engine, the work can take from several hours to one day.

Often, exhaust valves burn out on the block head, burnout can occur:

due to low-quality gasoline;
due to insufficient valve clearance;
due to the formation of oil deposits in the combustion chamber.

In order to replace the valve, the block head must be removed in any case. If you have auto mechanic skills, the work of replacing valves is not particularly difficult, and in this case we do the repair of the block head with our own hands as follows:

remove the cylinder head;
we dry out the burnt-out valve and take it out;
we take a new valve, apply lapping paste on its chamfer and rub the valve along the seat;
The tightness of the valve seating is checked with gasoline or diesel fuel, which are poured into the combustion chamber. If the liquid does not leave the chamber, then the valve is ground well;
after lapping, we dry out the valve, install the cylinder head in place.

Replacing the guide bushings is not an easy task, as the bushings are also changed using the repressing method. It is important to install the new guide in the center, if the bushing is installed crookedly, the valve will have to be ground in for a very long time. After the guide sleeve is in place, its inner diameter is machined using a reamer.

In the model range of VAZ cars there are front-wheel drive and rear-wheel drive cars, and if only 8-valve cylinder heads are installed on the VAZ-classic, 16-cl. block head. Such cars as Lada Kalina, Priora, Lada Granta, VAZ 2110-12 are equipped with 16-valve cylinder head.

Repairing a 16-valve block head is more difficult, removing and installing the cylinder head is also more laborious work. In order to remove the 16-cl. WHA, we do the following:

merge antifreeze from the radiator;
remove the decorative cylinder head cover;
disconnect the air filter housing assembly with the mass air flow sensor and the air pipe;
we unscrew the nuts of the exhaust pipe of the muffler;
we disconnect all pipes going to the head of the block;
dismantle the timing belt cover;
unscrew the intake manifold nuts and dismantle the manifold;
remove the valve cover;
remove the fuel rail assembly with injectors;
unscrew the fastening nuts and dismantle the thermostat;
remove the camshaft gears;
unscrew ten bolts of the block head;
dismantle the block head.

On many 16-valve engines, valve replacement may be required if the timing belt breaks.Car owners can make such a repair of the VAZ block head on their own, but the replacement of seats and guide bushings should be entrusted to professionals.

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An excellent substitute for such products will be ordinary gasoline, which is able to wash away carbon deposits, plaque and even the remnants of an old gasket that has become attached to the body.

The first malfunction, due to which it will not be possible to repair the head mechanism, is a violation of the seal. It will not be possible to repair such a case due to the fact that it must be monolithic, ensuring correct operation and heat resistance. There are two methods by which you can determine if the enclosure is airtight.

The first method is based on pouring water inside and waiting for it to flow outside. In order to check the case in this way, you will need to plug all the holes, except for the one through which water will be supplied inside. Water must be supplied under pressure, this can be done by a plunger pump.In this case, after pouring the liquid, you need to leave the case for a while, usually after an hour, water leaks already appear, but you need to wait for them up to 2 hours. If no traces are found during this time, then the tightness is in order. The main advantage of this method is that such a check can be done by hand.

As already mentioned, there is a second way of checking, it consists in pouring kerosene into the chambers. This option is considered the most optimal because a plunger pump is not required. In this method, you just need to pour kerosene into the chambers and wait until it flows through the microcracks. The fact is that kerosene is considered one of the most liquid substances, so it is able to penetrate into all holes, even the smallest ones. In this case, it will take from one to three hours. It is this method that is most often used by those who repair the cylinder head with their own hands. So, if cracks were found through which kerosene flows out, then such a head should simply be thrown out, having removed all the essentials from it.

If, nevertheless, the head turned out to be intact, then you should start checking the following devices. The first on this list are the bearings and camshaft journals.

In order to measure the diameter of a bearing, there is a special device called a bore gauge, and a micrometer is used to measure the diameter of the journals. Both of these devices measure everything with an accuracy of 0.01 millimeters, except this device is most often sold in car stores together.

Also, there should be no obvious signs of wear on the necks, namely: scuffs, scratches, gaps and other defects.

The next thing to check is the condition of the valve stems. The bar must be measured in at least three places and at several points of the circle. This is very important because the rod can become oval and the exact wear of the rod cannot be understood. The difference between the top and bottom points should not exceed the 0.03 mm mark. If the rods do not pass the test, they need to be replaced, but it is not worth stopping the test for them.

The last thing to check is wear on the levers, tappets, rocker arms, and cams. This can only be done visually. In the case of rocker arms, it is necessary to check not only the surface for damage, but also for the gap with the axis, it should not exceed 0.07 mm. If the gap is larger and cannot be eliminated, then after the cylinder block is repaired, the engine will also make noise, as it did before.

Unfortunately, a person has not yet come up with such a device that would not break, and the cylinder head on a car engine is no exception. In order to maintain its performance, it is required to pay attention to it during operation, at least to see how tightly the gasket holds, whether it does not leak oil. Most often, repairing the cylinder head is a rather laborious process, but it is still possible to do it.

Has the engine lost its thrust, throttle response, the oil level began to fall, the compression in the cylinders has fallen unevenly? It's time to start repairing the cylinder block.

Checking and repairing the cylinder head

We remove the cylinder head, clean it with an iron brush on a drill from carbon deposits and assess the condition of the valves. If there is no wear on the valve stem and the plates have no visible cracks, we check the cylinder head for leaks. To do this, pour kerosene into the chambers and leave for a day. If after a day the kerosene is in place, then everything is in order with the head, and further repairs are not required. If kerosene leaves one or more chambers, the cylinder head must be dried and replaced. You also need to replace the valve stem seals. To remove them, there is a special puller, or you can use pliers. You will also need a special tool to fill the valve stem seals.We also check the condition of the valve guides - they should not have cracks or chips. If cracked, the bushings must be replaced. We knock out the old bushing with a hammer and a punch, and in its place we hammer in a new repair size (with a tolerance of + 0.3 mm) guide bush. The surface of the cylinder head must be sanded, or milled (if there are deep scratches, or plans to increase the compression ratio of the engine).

It's time to check the cylinder block. Visually inspect for cracks, scoring, chips. If the cylinders have an excellent surface, the hon is in place, the pistons are without chips and cracks, then everything is in order with the block and the problem will be eliminated by one cylinder head repair. If there are visible scratches, grooves on the cylinder walls, then the block must be taken to the factory, where the cylinders will be bored to the repair size. It is also necessary to check for runout and balance the crankshaft. When replacing the crankshaft, the new one must also be balanced with the flywheel. This will keep the engine running smoothly. The surface of the block must be sanded.

After boring the cylinders, the block must be assembled on new oversized components. We buy new pistons, rings, connecting rods, crankshaft liners. For pistons and connecting rods, it is necessary to carry out weight distribution - the deviation in weight should not exceed 10 grams, otherwise the engine will be unstable. If the difference in weight is exceeded, the spare parts must be replaced at the seller.

So, the crankshaft is balanced, the block is assembled. We buy a gasket between the cylinder block and the cylinder head, and assemble it. The assembly is best done with a torque wrench in order to maintain the required tightening torque.

If the head of the block needs to be repaired, it must be removed from the engine. The exception is work on replacing some seals - for example, valve stem seals. Before starting work, it is worth acquiring spare parts, including a head gasket and all gaskets and oil seals located above it.

Before dismantling, it is advisable check the relative position of the crankshaft and camshaftby matching the corresponding marks. For some engines, such an operation is not necessary, but for some engines with complex valve timing, it is even useful to apply additional marks.

Usually, the technology for dismantling the head is described in detail in the repair manuals for auto specific models. But there are some techniques, among which the following are worth noting. When unscrewing the head mounting bolts, they are first loosened one by one by 0.5-1 turn, starting with the middle ones, and only then they are completely turned out. This prevents the head from warping due to uneven forces when one of the adjacent bolts is fully tightened and the other is released.

After removal, the head must be completely disassembled and the valves removed. Lever-type devices are used to remove the valve springs. In the absence of these, you can use traditional pullers.

Some "craftsmen" disassemble the head with a strong blow of a hammer on the spring plate through a steel pipe. This should not be done, especially if old valves are to be used. After "shock" disassembly, notches from the spring plate always remain on the valve stem, and just in the place where the valve stem goes. It is easy to bend the valve, especially if it has a thin stem. Yes, and crackers with such a disassembly have a habit of flying away in an unknown direction.

The lower plane of the head. You will need a special ruler with a length of 350 mm and a set of probes. The ruler is alternately placed on a plane along the diagonals of the head and a probe is selected that freely passes into the gap between the ruler and the plane in the middle zone. The maximum allowable thickness of this stylus is 0.05-0.06 mm, otherwise the plane will have to be processed.

Worn camshaft bearing journals and bearings. The diameters of the journals are measured with a micrometer, and the diameters of the bearing bores are measured with an internal gauge with an accuracy of 0.01 mm. The difference in the dimensions obtained gives the bearing clearance, which should not exceed 0.10 mm. In this case, the surfaces to be inspected should not have obvious signs of wear - circular grooves, protrusions, scoring, etc. Otherwise, the camshaft is replaced and the head is repaired.

Worn valve stems and guide bushings. The diameter of the rod is measured with a micrometer in the upper part, directly under the groove for crackers, and then in the lower part of the working surface. Since a worn rod can be oval, measurements should be taken at several points around the circumference. Wear, that is, the difference between the diameters in the upper and lower parts of the rod, should not exceed 0.02-0.03 mm, otherwise the valve must be replaced.

The wear of seats, pushers, levers, rocker arms, cams is determined visually. Valve chamfer wear can be assessed by placing a ruler on the chamfer and looking at a bright light. If the middle of the chamfer is “dropped” and the rod is not worn out, then the chamfer can be machined and the valve can be used again. In the rocker arms, in addition to the condition of the surfaces in contact with the valve and the cam, it is necessary to check the clearance with the axis - it should not exceed 0.06-0.07 mm. Otherwise, the engine after repair of the head will remain noisy, as it was before.

Various local defects are also identified visually. Here it is necessary to pay attention to the state of the surface of the head in contact with the gasket edging: notches, burrs and other defects lead to leaks in the connection of the head to the cylinder block. Sometimes it is also possible to see cracks in the walls of the combustion chamber. If the crack is through (into the cooling jacket), then there will be no carbon deposits on the walls either near the crack or throughout the chamber.

When there is a suspicion that a crack has appeared in the combustion chamber, the head must be checked for leaks before repairing, otherwise all repairs may be in vain.

Video (click to play).

To pressurize the block head, it is necessary to tightly seal all the windows of the cooling jacket facing the lower plane, as well as all flanges and nozzles on the side surfaces, except for one through which the liquid will flow. The head is pressurized with water supplied by a special hand plunger pump under a pressure of 0.6-0.8 MPa. Cracks are detected by a drop in pressure during a control time (from a quarter of an hour to two hours) and the appearance of water droplets or leaks.