A block is the main part of almost any internal combustion engine. It is to the cylinder block (hereinafter referred to as BC) that all other details are attached, starting from the crankshaft and ending with the head. BCs are now made mainly of aluminum, and earlier, in older models of cars, they were cast iron. Damage to cylinder blocks is by no means uncommon. Therefore, it will be interesting for novice car owners to learn about how to repair this unit. Let's find out about typical breakdowns, as well as about methods and technologies for repairing the engine block. This information will be interesting for everyone who owns a car.
Short device
Directly inside the block there are through holes with polished walls - pistons move inside these holes. In the lower part of the BC a bed is made on which the ends of the crankshaft are fixed through bearings. A special surface was also made there to secure the pallet.
On the upper part of the block there is also a perfectly smooth polished surface. A bolt is attached to it with bolts. What many today call cylinders is formed from a block and a head. On the side of the BC there are brackets for mounting the engine to the car body.
Sleeves can be installed inside the cylinder. They are widely used in aluminum blocks. Each part that is attached to the motor is equipped with gaskets that prevent possible engine leaks. Thanks to these elements, antifreeze does not mix with oil and vice versa. Gaskets should always be intact, otherwise this will adversely affect the operation of the engine.
Typical malfunctions
Before you deal with the topic of repairing the engine block, it is necessary to familiarize yourself with the most common problems with this unit. Some problems can be eliminated on their own in a garage environment; others will require special equipment.
During engine operation, the following types of defects may form in the engine block. This is a natural wear of the cylinder walls, scuffs and risks on the walls. Also, cracks of both cylinders and a water jacket or cylinder head are often formed. Valves are also subject to wear. They may also form cracks or shells. Studs, as well as bolts, fastening the cylinder head to the block itself break.
There are less serious problems - this is scale in the shirt of the cooling system, as well as carbon deposits in the cylinder head. Due to the corrosion processes, the operation of the unit at elevated temperatures, the friction of the pistons and crankshaft against the cylinder walls, they eventually acquire an ellipse in the plane where the connecting rod sways. A taper is also formed along the length of the cylinders.
Causes of wear
When the fuel burns in the combustion chamber, the gases enter the grooves of the piston rings and squeeze them strongly to the cylinder mirror. The pressure force decreases as the piston moves down. Therefore, the cylinders wear out more at the top than at the bottom. As for the lubricant, in the upper part of the cylinders it is worse due to exposure to high temperatures. The force that acts on the piston in the engine during its stroke is divided into two important components.
The first part of this force is directed along the connecting rods. The second part is directed perpendicular to the axis of the cylinders. She presses the pistons to the left side of the wall. When compression is transferred from the crankshaft to the connecting rod, the force also decomposes into two parts - one works along the connecting rods and compresses the fuel mixture, and the second presses the piston to the right cylinder wall. Lateral forces also work on the intake and exhaust strokes, but to a much lesser extent.
As a result of the lateral forces, the cylinders have wear in the plane of the connecting rod and an ovality is obtained. The wear of the left wall is more significant, since the lateral force during the working strokes of the pistons is the highest.
In addition to the formation of ovality, the influence of lateral forces also causes tapering. As the piston moves downward, the lateral forces are reduced.
Scuffs on the cylinder walls are formed due to overheating, oil starvation, oil contamination, insufficient gaps between the cylinder walls and the piston, poorly fixed piston pins, due to breakdown of the piston rings. How badly the cylinder is worn can be determined using an indicator or caliper.
How to measure wear?
Ovality or ellipse should be measured in the belt, which is located 40-50 mm below the top of the combustion chamber. You need to measure in planes that are mutually perpendicular. Depreciation will be minimal along the crankshaft axis, and maximum - in that plane that is perpendicular to the crankshaft axis. If there is a difference in size, then this will be the size of ovality.
To determine the taper, the indicator should be installed along the combustion chamber. The plane is chosen perpendicular to the axis of the crankshaft. If there is a size difference in the indicator readings, then this is the size of the taper. In this case, the lower and upper parts of the cylinder must be measured. The indicator is lowered strictly vertically so that it does not deviate to either side.
If the ellipse size is higher than the allowable 0.04 mm, and the taper is more than 0.06 mm, there are scuffs and risks on the walls, then the engine block of the engine needs repair.
By repair you need to understand the increase in diameter to the nearest repair size, the installation of new pistons and other related elements. Depending on how worn the cylinders are, they are ground, bored, and then adjusted, liners are installed.
BC grinding
This operation is carried out mainly on intra-grinding machines. The stone on this equipment has a significantly smaller diameter than the size of the cylinder. The stone can move around the axis, around the circumference of the cylinder, and also along the axis of the combustion chamber.
The repair process of the engine block, thus performed, is very long and complicated, especially if you need to remove a large layer of metal. The surface of the combustion chamber becomes wavy and may become clogged with dust. The latter penetrates into the pores in cast iron - after repair in the future, this can cause intense wear of the rings and pistons. Grinding cylinders is now rarely used.
Boring
Repair of cast iron engine blocks can be performed in this way. Use boring stationary and mobile machines. Mobile vertical boring units are attached in the process directly to the block. In this case, for processing the first and third cylinders, the machine is fixed from above with bolts that are passed through the second cylinder. Before finally fixing the machine, its spindle is carefully centered using cams. The cutter is adjusted to the required size using a micrometer or caliper.
The minus of boring is considered the need for subsequent fine-tuning - on the surface without finishing there are traces of the cutting tool. The debugging during the repair of the cylinder block of the diesel engine, gasoline units is performed in special or drilling machines. In simpler cases, you can do with an electric drill and a lapping head with abrasive stones. During any refinement, the treated cylinder is abundantly watered with kerosene.
At the end of processing, the taper and ellipse should not be more than 0.02 mm. Diamond boring is performed by carbide cutters at low feeds and high speeds. It is better to work on special boring machines.
Sleeve
This technology for repairing the engine block is selected when cylinder wear is greater than the last repair size. Also choose a liner if there are very deep burrs and risks on the surface.
The cylinder must be bored to a diameter that allows you to install a sleeve with a wall thickness of up to 2-3 mm after boring. In the upper part of the combustion chamber, you need to make a special undercut for the sleeve for the sleeve.
The sleeve is made of materials that are close in properties to the material of the cylinders. The outer diameter must have an allowance for pressing. The liner, as well as the cylinder walls, are lubricated with oil and pressed with a hydraulic press. If there is no press, the sleeves can be installed using a manual device.
Repair of valve seats
Along with the BC, it may be necessary to repair the engine head. If the wear of the valve seats is small, this can be eliminated by simply grinding the valve to the seat. If the wear is significant, then the saddle is milled with a cone mill. The first step is to process a roughing mill with an angle of 45 degrees. Next, choose a cutter with an angle of 75 degrees. After they take the part at an angle of 15 degrees. Then the saddle can be machined with a finishing mill.
Milling will be effective only if the valve guides have minimal wear or even new ones.
In the process of repairing the engine block 406 after milling, the saddle is polished with cone stones with a drill and the valve is rubbed. If the wear of the saddles is large, then the socket must be bored on the machine with face mills and a cast-iron ring is pressed into it, which then needs to be processed in the above sequence.
If it is possible to replace the replacement seat, then to facilitate repair of the cylinder head 406 of the engine, simply replace the old seat with a new one.
Valve Sleeve Repair
If the valve guide bushings are worn, then they can be restored by deploying a long scan to the repair size. If the sleeve wear is significant, then they should be removed under the press and replaced with new ones. When pressing in new bushings, the interference must be 0.03 m. Then the diameter of the bush is deployed to the nominal size.
Repair guide rails
These elements, manufactured in the block in separate parts during the repair of the cylinder head 402 of the engine, are processed by deploying the pusher rod for repair dimensions or by replacing the pusher rods.
Conclusion
As you can see, it is impossible to carry out engine overhaul without special machines and special tools. But if the damage is minor, especially desperate craftsmen bore the cylinders with an ordinary electric drill with sandpaper. In fact, there is nothing terrible in overhauls - in most cases, the prices for boring and other operations are low. Repair of the cylinder head of a diesel engine can be done in the garage with your own hands by analogy with gasoline cylinder head.