DIY engine block repair

In detail: do-it-yourself engine block repair from a real master for the site my.housecope.com.

Locksmith and mechanical work during the repair of engine cylinder blocks includes preparation for welding and processing after welding of cracks and block breaks, replacement of bushings for camshaft journals, processing of holes for valve tappets, processing of the contact planes of cylinder heads, restoration of threaded holes, etc.

Cracks and holes in blocks can occur as a result of Impact, freezing of water in the cooling system, as well as sharp cooling of an overheated engine. Before welding, the crack is cut at an angle of 120 ° to a depth of 3-4 mm and holes 0 3-4 mm are drilled at its ends. For cutting cracks, a pneumatic machine with an abrasive wheel is mainly used. The surface of the metal around the crack is 15–20 mm cleaned of rust and dirt.

Cracks are welded with an intermittent seam, followed by welding gaps in the welded seams.

Cracks passing through the lower bridges between the cylinders are repaired by welding with the welding of the bar to the bridging and placing tie rods on epoxy resin.

A steel plate 2.0-2.5 mm thick is applied in place of the hole so that it overlaps the crack along the perimeter by 10-15 mm. After that, the plate is tapped with a hammer so that it takes a concave shape to compensate for linear expansion during welding, and then it is welded with an intermittent seam.

To seal the welds, a layer of epoxy is applied to them. Holes can be repaired of almost any size and nature. After elimination of defects by welding, the cooling jacket of the cylinder block is tested on benches for tightness with water under a pressure of 4 kg / cm2 for 2-3 minutes.

Video (click to play).

For manual cold electric arc welding, the following equipment is used: welding transformers ТДП -1, ТС-300, -500, TD-300, -500; welding rectifiers VDG -301, -302, -303; as well as single-station welding converters and assemblies PSO - ZOZ -Z, PS-500 and SAM-300-2 (the latter can be used to work in air and in the rain). This unit uses a splash-proof generator.

Cracks on the walls of the water jacket of aluminum blocks (and heads) are welded or fused with argon-arc welding. Compared to other methods, this welding has a number of advantages: reliable gas shielding of the weld pool from the ambient air preserves the chemical composition of the metal of the welded joints as much as possible; concentrated arc action provides slight distortion of the part; there is no need for preliminary general heating, which significantly reduces the labor intensity of welding. For argon-arc welding, UDG -301 and -501 installations are used.

Holes with worn or damaged threads are repaired by oversized threading, welding of holes followed by threading of nominal size or spiral threaded inserts.

The insert is a springy spiral made of rhombic wire (Fig. 1). At one end of the spiral, a technological leash is bent, by means of which the insert is wrapped in a previously prepared hole.

The technological process of repairing a threaded hole using a spiral insert includes the following operations: reaming the defective hole to a certain size, cutting a thread in it corresponding to the size of the spiral insert, screwing in the spiral insert and breaking off the technological leader along the notch.

For the repair of threaded holes with spiral inserts, a special kit is produced, which, in addition to inserts, includes tools: drills, special taps, keys for screwing inserts, barbs for cutting off a technological leash.

Performing operations when repairing holes with spiral inserts is not particularly difficult.The defective hole is drilled out, a thread is cut in it for a spiral insert and, using a special key, it is screwed into the hole until the last turn of the insert is 0.5 mm below the level of the main surface. After that, a beard is inserted into the hole and the technological leash is cut off.

Since in the free state the outer diameter of the insert is slightly larger than the diameter of the hole to be repaired, then after being screwed into the threaded hole, the insert is in a stressed state and is held in the hole quite firmly.

The practice of restoring parts has shown that the method of repairing defective threaded holes using spiral threaded inserts is effective and expedient for most threaded holes in car body parts. The exception is heavily worn threaded holes, the diameter of which is larger than the outer diameter of the insert. Such holes are sometimes found in the cylinder block (under the head studs), in the gas pipeline (under the muffler exhaust pipe flange), in the clutch housing (under the starter bolts).

The repair of threaded holes in automobile parts by the method of setting spiral threaded inserts in comparison with the repair with the help of threaded bushings (screwdrivers) or cutting a new (repair) thread provides an increase in the wear resistance of threaded connections, eliminates the possibility of jamming of screwed-in parts, significantly increases labor productivity and reduces the cost of repairs. ...

Worn and deformed seats for main bearing shells are restored mainly in two ways. In the first case, the worn surfaces of the sockets for the inserts are fused with PMTs54 hard solder or L62 brass using an acetylene-oxygen torch. The thickness of the deposited layer is 1.5-2.0 mm. Then the surfaces of the main bearing caps are milled or ground to a depth of no more than 0.3 mm. After that, the covers are assembled with the cylinder block. The tightening torque of the mounting bolts is 11-13 kgf-m for engine blocks ZIL-130 and 30-32 kgf-m for YaMZ-238. Further, the seats of the main bearings are bored into a line to the nominal size on special two-spindle horizontal boring machines. On these machines, the boring of the main bearing seats is carried out simultaneously with the boring of the camshaft bushings. Simultaneous boring ensures the nominal distance between the axes of the main bearing seats and the camshaft bushings.

The misalignment of the bored holes should be no more than 0.02 mm for the ZIL -130 engine along the block length, and the runout of the bored sockets of the middle supports relative to the extreme ones is allowed no more than 0.025 mm for the YAME-238 engine.

A less time-consuming and most promising method of restoring the main bearing seats is the method of setting compensating plates (under the liners), which consists in the following. Before boring and inspecting bored cylinder blocks, the main bearing cap bolts and nuts must be tightened to a torque that meets the specifications previously specified. Further, simultaneous boring of the main bearing seats of the blocks is carried out for the installation of compensating plates.

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After control operations and interoperational washing, compensating plates are installed in the cylinder blocks and covers, then the block is fed to the assembly.

Compensating plates are installed in the block so that the tab of the insert enters the groove of the plate and it protrudes above the plane of the cylinder block AND the cover connector.

Plates are made by stamping from high-precision tape, material - steel 50. Plate thickness is 0.3 mm for YAME-238 engines and 0.25 mm for ZIL-130 engines.

What are we going to repair in the cylinder block?

Cylinder block repair technology, at its core, requires the use of specialized boring or honing machines. Although, in some cases, when repairing the engine block with your own hands, you can also use a manual honing head for an electric drill.

Repairing the cylinder head, or replacing the cylinder head gasket, can also partially be attributed to the repair of the cylinder block. But, we will focus specifically on the repair of the cylinder block.

As qualified professionals, we are well aware that before taking on the hammer, we need to figure out what detail we will knock on. That is, we are talking about traditional malfunctions in which repair of the cylinder block is simply necessary.

Wear on cylinder surfaces. This is the main defect, but not the only one. Cylinder repair is usually limited to cylinder boring and honing. Thus, the ellipticity arising from the peculiarities of the piston operation is removed, scratches and scuffing of the cylinder surface are removed.

Severe cylinder wear can occur due to a large axial clearance in the crankshaft thrust bearing. The most common is considered to be "natural" wear of the cylinder surface. It occurs as a result of long-term operation in normal mode. It appears in the upper part of the cylinder in the TDC (top dead center) zone at the moment the piston enters it.

Broken connecting rod. As a rule, a connecting rod breakage and subsequent chips and holes in the lower part of the cylinder occur due to overheating of the connecting rod bearing. This is the result of insufficient lubrication of the bearing.

A broken valve or ruptured seat will result in damage to the top of the cylinder. In this case, scuffs or bumps appear on the surface of the cylinder.

Cracks in the liner. This defect is rare, but it does occur. Over-tightening or improper tightening of the cylinder head bolts can cause this crack.

Cylinder seizures are often a direct result of engine overheating. In all these cases, cylinder repair is required. The event is not fast and expensive. The listed defects and malfunctions requiring repair of the cylinder block are obvious.

What cylinder block malfunctions are not immediately visible
They are not visible, but they are. Not knowing about these malfunctions means that the repair of the engine block of cylinders can turn into an unpleasant epic. When, after repairing the cylinder block, after tens of thousands of kilometers, the engine fails again.

Block deformation. This can happen due to a violation of the manufacturing technology of the block, when the internal stress has not been removed. This is especially true for cast iron blocks. For this, there is such a technology for repairing a cylinder block as artificial aging. Heating the block at a certain temperature and then machining: milling planes, boring cylinders and crankshaft beds
. Another reason for the deformation of the cylinder block itself is the unevenness of its heating during operation.

Repair of the crankshaft bearing bed. It is required both due to natural deformation and due to overheating or lack of lubrication of the main bearings. Against the background of the listed malfunctions, the breakdown of the stud or thread of the cylinder head bolt is a trifle for a mechanic. In this case, a hole is bored and a thread is cut.

From the list of all possible malfunctions of the cylinder block, it can be concluded that the technology for repairing the engine block in each case may be different. Do-it-yourself cylinder block repair in full, you are unlikely to be able to perform 100% in a garage, since certain operations require special equipment.

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The smoke from the exhaust pipe is white, black, and other shades.At the same time, color serves as an important diagnostic feature and sometimes directly indicates malfunctions in the engine. We will talk about them.

As you know, the engine block is the basis of any internal combustion engine. In fact, the block is a three-dimensional part, inside which various assemblies and mechanisms are located (pistons and rings, as well as CPG sleeves, crankshaft, KShM connecting rods, etc.).

It is not surprising that damage to the cylinder block will not only disrupt the performance, but also disable the power unit. For this reason, the restoration of the block and its repair must be carried out efficiently and in a timely manner.

To begin with, there are two types of cylinder blocks:

cast iron BC;
blocks of aluminum alloys;

As a rule, cast iron blocks are additionally hardened with graphite, and lightweight aluminum products are made liner (a cast iron liner is inserted into the block). There are also aluminum cylinder blocks without liners. The alloy includes silicon, which significantly strengthens the block.

As for the sleeve blocks, the sleeves are "wet" and "dry". In the first case, the coolant is in direct contact with the sleeve, while in the second, the sleeve is tightly pressed into the block body during manufacture.

One way or another, each solution has its pros and cons, and during operation, various damages and defects of the cylinder block or defects of the block liners occur (depending on the type of BC).

Also, wear of the cylinders in the direction of the crankshaft axis often occurs. As a rule, cylinder damage on a "fresh" engine is caused by engine overheating or water hammer, as well as a decrease in the level or significant loss of the properties of the engine oil.

Less commonly, the cause of block defects is the unexpected destruction of the piston rings and other unforeseen breakdowns. We also add that in the BC there is often deformation of the crankshaft bearing bed, etc.

With regard to the wear of the cylinder surfaces, in this case, such wear is often "natural", that is, it is the result of operating the engine in normal operating conditions. The repair of cylinders itself in this case often involves boring and honing the cylinder (applying hone). This allows you to remove the ellipseness of the cylinder, remove scratches and scuff marks on the mirror.
A more difficult case can be considered a broken connecting rod,
as the damage is usually more serious. Also, the cause of block defects is valve breakage, destruction of the valve seat, etc. The result is scuff marks on the cylinder surface and other damage. Also, in the list of common malfunctions, cracks in the block or sleeve should be highlighted.
We also add that there are so-called "hidden" problems, that is, it can be difficult to identify defects visually within the framework of a superficial examination. At the same time, unqualified repairs, which are limited to the banal replacement of worn parts, will still lead to the fact that the engine will need to be disassembled again after several hundred or thousand kilometers.

By the way, this problem is more inherent in cast iron blocks. Also, overheating of the engine or its uneven heating during operation can lead to deformation of the block (both cast iron and aluminum).

So, the repair of the cylinder block and the restoration of the cylinders themselves involves:

thorough cleaning of BC surfaces;
then a check is made for the tightness of the channels of the cooling system in the block (cooling jacket);
also washed and cleaned, and then the oil channels are checked;
further, an inspection of the cylinders is carried out in order to identify various defects;
then the block is bored / bored, surfaces are ground, etc.

For many engines, cylinder boring is a mandatory procedure as part of an engine overhaul.To perform the procedure, a special machine is used for boring engine cylinders. The boring of the block itself should be understood as the processing of the inner surface.

Such processing actually represents the removal of a layer of metal to level out irregularities, remove scoring, smooth out cavities, etc. The main task of machining is to give the cylinders their normal shape (cylindrical).

Another cylinder block repair may involve liner or re-liner. In the first case, the installation of the liners should be understood, although the factory design does not initially imply this. In the second, the worn out sleeve is removed from the block, after which a new repair is installed.

Finally, we note that as part of the restoration of the block, it may be necessary to repair the crankshaft bearing bed. Also, in some cases, it becomes necessary to eliminate the deformation of the block. For this, the method of artificial aging is used, when the block is heated to a certain temperature, after which various areas are treated.

As you can see, there are many faults in the cylinder block itself. Some can be considered small (for example, if a bolt breaks off in a block, etc.), while others are serious enough (for example, wear on the cylinder walls, cracks, etc.)

In practice, this means that in some cases it is possible to restore the cylinder block with your own hands even in a garage, while in others it will be necessary to have special equipment (machines for boring the block, honing, grinding). Also a very important aspect is the experience and qualifications of the master himself.

In view of the above, it becomes clear that only experienced specialists should be entrusted with the performance of such work, and the engine itself should be optimally repaired at such service stations, where it is possible to perform all the necessary operations right on the spot. First of all, this will shorten the repair time, and can often serve as a quality guarantee.

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What does overhaul of a car engine mean, what work is being done. What determines the engine resource before overhaul and how to increase it. Helpful hints.

The cylinder block is the main engine component. In it and on it, exactly what we call the engine is located and fastened. Traditionally, the cylinder block was made of cast iron, now aluminum is increasingly used.

Cylinder block repair technology, basically, requires the use of specialized boring or hotting machines. Although, in some cases, when repairing the engine block with your own hands, you can also use a manual hotting head for an electric drill.

As qualified professionals, we are well aware that before taking on the hammer, we need to figure out what detail we will knock on.That is, we are talking about traditional malfunctions in which repair of the cylinder block is simply necessary.

Wear on cylinder surfaces. This is the main defect, but not the only one. Repair of cylinders, as a rule, comes down to boring and hotting of the cylinder. Thus, the ellipticity arising from the peculiarities of the piston operation is removed, scratches and scuffing of the cylinder surface are removed.

Broken connecting rod. As a rule, a connecting rod breakage and subsequent chips and holes in the lower part of the cylinder occur due to overheating of the connecting rod bearing. This is the result of insufficient lubrication of the bearing.

Valve break or a ruptured seat will result in damage to the top of the cylinder. In this case, scuffs or bumps appear on the surface of the cylinder.

Cracks in the liner. This defect is rare, but it does occur. Over-tightening or improper tightening of the cylinder head bolts can cause this crack.

They are not visible, but they are. Not being aware of these malfunctions means that the repair of the engine block of cylinders can turn into an unpleasant epic. When, after repairing the cylinder block, after tens of thousands of kilometers, the engine fails again.

Block deformation. This can happen due to a violation of the manufacturing technology of the block, when the internal stress has not been removed. This is especially true for cast iron blocks. For this, there is such a technology for repairing a cylinder block as artificial aging. Heating the block at a certain temperature and then machining: milling planes, boring cylinders and crankshaft beds. Image - DIY engine block repair

Another reason for the deformation of the cylinder block itself is the unevenness of its heating during operation.

Repair of the crankshaft bearing bed. It is required both due to natural deformation and due to overheating or lack of lubrication of the main bearings.

Against the background of the above malfunctions, the breakdown of a stud or thread of a cylinder head bolt is a trifle for a mechanic. In this case, a hole is bored and a thread is cut.

Good luck with DIY cylinder block repairs.

And so, we came to the finish line. In our Mitsubishi 4M41 engine, which has traveled half a million kilometers, after repair cylinder head and chain drive Timing it remains to deal with the crank mechanism and the cylinder block. By the way, the most pessimistic forecasts were voiced precisely by the state of the cylinder block - after all, such a run could not but affect the geometric characteristics. However, after a complete revision of the block, this engine finally fell in love with our master.The cylinder block is a metal body part, which contains the elements of the same crank mechanism, due to which the translational movement of the pistons turns into a rotational movement of the crankshaft.There are cavities inside the block, which, when the motor is running, are filled with coolant - a water jacket. The blocks are made of cast iron or aluminum alloy: the block itself must be massive, because it perceives rather weighty shock loads transmitted from the pistons. Also, do not forget about heating, the consequences of which must be minimized.From above, the block is covered with a block head (cylinder head), from below - with a sump. In the block itself there are sleeves, inside which the pistons move. The inner surface of the liner, which is in direct contact with the piston, is called the cylinder bore. In the lower part of the block there are "beds" - lodgments, in which the crankshaft is placed, covered with covers. When the bed is covered with a lid, a hole is formed, called the crankshaft main support.It is important that the cylinder block is rigid enough, since the forces that arise during operation try to twist, bend and break the block - which is why it remained cast iron for many decades. The trend of our time is lighter cylinder blocks made of aluminum alloy, with which (as well as with lightweight cast iron) they use integrated main bearing caps, called a ladder frame.So, it turns out the following: in the classic version (like ours, for example), each main journal of the crankshaft is covered with a separate main bearing cap (it is often called a yoke). In a ladder-type frame, all the yokes are combined into one structure, similar to a ladder - thus the designers have achieved a significant increase in the rigidity of the cylinder block. The disadvantage of this approach is the cost of manufacturing such a part.The tendencies of the modern automotive industry are such that classic cast iron blocks for several piston repair sizes have already become an endangered species, where engines are more often “disposable”. No.Having dealt with the block, we turn to the moving parts - and the pistons will be the first. They are made of aluminum alloy and structurally have a skirt, bottom and lugs. The skirt is the side of the piston, the bosses are the tides, in which a hole is made for the piston pin, and the bottom is a plane facing directly into the combustion chamber and directly taking all the loads during the combustion of the fuel-air mixture. It is interesting that the piston crown can be flat, like a cabinetry jig, or it can have such a complex shape that it will be difficult to understand the first time that it is a piston.The complexity of the piston shape, if any, has been carefully calculated in order to improve the mixing of fuel with air (which is often found in gasoline internal combustion engines with direct fuel injection). If the engine runs on a diesel engine (like ours), there may be a combustion chamber in the piston, and it itself will be much more massive than its gasoline counterpart.The piston is installed in the cylinder with a certain clearance (often 0.2–0.3 mm), therefore, piston rings are provided to seal it. On modern engines, the piston is surrounded by two compression rings and one oil scraper ring. The piston is connected to the crankshaft through a connecting rod - a connecting element. One end of it is attached to the piston through a pin, which is pressed in or simply inserted and locked with rings in the piston and the connecting rod head. The second end is collapsible: to secure it to the crankshaft, you must install the connecting rod cover and tighten its bolts or fastening nuts.Both the crankshaft with the block and the connecting rods with the crankshaft are in contact through plain bearings, they are liners. For additional cooling of the pistons, oil diffusers can be installed inside the block, directed to the pistons.The inline-six is considered one of the most balanced engines (in terms of vibration).We have an in-line "four", and an impressive volume, and therefore two balancer shafts are installed in the cylinder block, the essence of which is to reduce engine vibrations.Piston rings are one of the most vulnerable parts of the engine: because of carbon deposits, they can literally stick. In this case, the rings themselves can burst, or the bridges on the piston, between which they are installed, can burst. Finally, the selection under the ring in the piston may wear out directly.There are no more or less critical elements in the engine, but still there is a mechanism, the incorrect assembly of which can only be revealed after the installation is completed and the engine is attempted to start. Yes, it is trying - and often.

There are fewer potential problems with the pistons themselves, but this does not alleviate the situation. The simplest thing that can happen is trivial wear and tear and deviation from the nominal diameter, while complete "trash" is a piston burnout. In addition, wear on the piston pin and the pin bores in the piston pin bores is possible.With the connecting rod, everything is even easier: there are two nuances that are always checked, and two that are often ignored. The first is the wear of the bushing of the small connecting rod head and the wear of the connecting rod bearing shells, and the second is the amount of bending and torsion of the connecting rod. Nevertheless, as practice shows, the connecting rod is one of the most rarely replaced elements in the engine.The most common problem with the crankshaft is the wear of the working surfaces, the second most popular place is the cases of cranking the liners. This happens when there is not enough oil at the point of contact, which is why the crankshaft tears off the bearing shells and starts to "cheerfully" rotate with them. This is a really tough case: with a certain amount of bad luck, repairs can be worth replacing the unit.Wear of the crankshaft thrust rings is also a rather unpleasant problem, albeit insignificant at first glance. The point here is that a defect that is not detected in time in the future can lead to engine jamming - after all, forces act on the crankshaft during operation in the longitudinal direction too. It is enough to displace the shaft at a critical distance - and the pistons will simply jam from skewing. It is worth noting that breakage of the "knee" itself is also possible, although you will have to try for this.In the block itself, there is practically nothing to break down constructively - but this does not mean that there are no problems with it, quite the contrary. The most common are cylinder wear or warpage of the contact surface of the block with the head due to overheating. Especially careless car owners, however, can break the cylinder block itself. To do this, you just need to perform a couple of simple operations: the first is to fill the cooling system with ordinary water (distilled water can be used), and the second is to leave the car on the street overnight at minus 20 ° С.First of all, after disassembly, the outer diameter of the pistons is measured in a strictly defined plane (across the axis of the pin) and at a given distance from the surface of the piston crown. The manufacturer can manufacture pistons in several sizes: nominal and repair - these data are given in the technical documentation. If the piston is in "nominal" (as it turned out with us), check the runout of the connecting rod and pin. A professional can detect something amiss, as they say, by touch - an inexperienced mechanic will still have to squeeze a finger out of the piston and connecting rod. After pressing out, it is necessary to measure the outer diameter of the pin and the inner diameters of the connecting rod bushing and the holes in the piston, use simple mathematics to calculate the clearance in this assembly and make a final decision on the disposal or further use of this kit.Armed with a set of flat probes, mechanics measure the gap between the ring and the piston recess: if it is exceeded, the piston is sent for replacement.Since we are carrying out major repairs, the replacement of rings is not even discussed - this is a self-evident fact.The inline "four" 3.2 TD of the 4M41 series is far from the worst representative of the family of modern turbodiesels. Having pulled two and a half tons of Japanese iron in the face of a 2006 Mitsubishi Pajero Wagon in 10 years, this one.Having almost finished with the moving elements, we turn to the cylinder block, for the measurement of which a so-called internal gauge is needed. This is a device designed to measure the inner diameter with high accuracy, which is provided by a dial indicator. The inner diameter is measured at three levels and in two mutually perpendicular planes: this is necessary for the most accurate understanding of the magnitude and nature of cylinder wear. The nature of wear in this case is the amount of barrel-shaped and ovality of the cylinder. The thing is that the load on the cylinder is uneven, and, therefore, its wear is also uneven: closer to the center, the amount of wear will increase and then decrease again. Because of this, the cylinder in the profile section is slightly "rounded" and becomes like a barrel. In turn, the piston presses on the cylinder in only one direction, producing a surface and turning it into an oval one. I repeat, the accuracy when working with the block must be extreme - there simply cannot be any approximate dimensions: the technical documentation necessarily contains figures for the maximum permissible barrel shape and ovality of the cylinders.In the end, the crankshaft is also revised. They measure the diameters of the main and connecting rod journals and, if necessary, grind to the next repair size, if any. With the help of an internal gauge known to us, the diameters of the holes of the main supports are measured (with the liners installed, of course). Then, having the outer diameter of the journals and the inner diameter of the supports, the oil gap is determined: if it exceeds the allowable one, the liners are sent for replacement, and the crankshaft is sent for grinding. In addition, above we mentioned the axial play of the crankshaft - of course, during troubleshooting, it is also measured, and if the play is too high, the thrust rings of the crankshaft are replaced.If the condition of the cylinders does not at all allow the block to continue to operate, it is sent to the cylinder bore to the next overhaul size. It happens that the manufacturer does not provide such luxury, then the block is “cased” - restored by casing. As you might guess, in this case, the existing sleeve is significantly bored and another sleeve with an inner diameter of the nominal size is pressed into it. However, this solution is no longer very reliable, and some masters predict no more than 50 thousand kilometers of potential run for such an engine.If the block is bored, then, of course, the pistons with rings are selected to the appropriate size. Grinding the crankshaft journals reduces their size - which means that for them it is necessary to select the liners of the next overhaul size. The work is facilitated by the fact that in the technical documentation there is usually a dimensional grid for the selection of liners.Before installing the pistons, the cylinder mirror is honed. This is a process that does not change the size of the cylinder, but due to which the wear of the rubbing surfaces is significantly reduced. Honing is making small marks on the surface of the cylinder using special stones. This is necessary so that the engine oil is retained on the surface of the cylinder, thereby increasing the resource of the piston group.