Repair of the engine block: step-by-step instructions with a description, device, principle of operation, tips from the masters

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

The block is the main part of almost any internal combustion engine. It is to the cylinder block (hereinafter referred to as the BC) that all other parts are attached, starting from the crankshaft and ending with the head. BCs are now made mainly of aluminum, and earlier, in older car models, they were cast iron. Cylinder block failures are by no means uncommon. Therefore, it will be interesting for novice car owners to learn how to repair this unit. Let's learn about typical breakdowns, as well as methods and technologies for repairing an engine block. This information will be of interest to anyone 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, through bearingsthe ends of the crankshaft are fixed. There is also a special surface for fixing the pallet.

On the top of the block there is also a perfectly smooth polished surface. The head is attached to it with the help of 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.

Liners can be installed inside the cylinder. They are widely used in aluminum blocks. Each part that is attached to the motor is equipped with seals that prevent possible engine leaks. Thanks to these elements, antifreeze does not mix with oil and vice versa. Gaskets must always be intact, otherwise it has a bad effect on the operation of the internal combustion engine.

Typical malfunctions

Before dealing with the topic of repairing the engine block, you need to familiarize yourself with the most common malfunctions of this unit. Some problems can be fixed on your own in the garage, to fix others you will need special equipment.

During engine operation, the following types of defects may form in the engine block. This is the natural wear of the cylinder walls, scuffs and risks on the walls. Also, cracks are often formed both in the cylinders and in the water jacket or cylinder head. Valve seats are also subject to wear. Also, cracks or shells may form on them. Studs break, as well as bolts securing the cylinder head to the block itself.

There are less serious problems - this is scale injacket of the cooling system, as well as soot in the cylinder head. Due to corrosion processes, operation of the block at elevated temperatures, friction of the pistons and crankshaft against the cylinder walls, they eventually become elliptical in the plane where the connecting rod swings. There is also a taper along the length of the cylinders.

Reason for wear

When the fuel burns in the combustion chamber, gases enter the grooves of the piston rings and force them against the cylinder bore. The force of pressure decreases as the piston moves down. Therefore, the cylinders wear more at the top than at the bottom. As for lubrication, it is worse in the upper part of the cylinders due to exposure to high temperatures. The force that acts on the piston in the engine during its working stroke is divided into two important components.

The first part of this force is directed along the cranks. The second part is directed perpendicular to the axis of the cylinders. It presses the pistons against 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 against the right wall of the cylinders. Lateral forces also work on the intake and exhaust strokes, but to a much lesser extent.

As a result of the action of lateral forces, the cylinders have wear in the plane of the connecting rod and an ovality is obtained. Significant wear of the left wall, since the lateral force during the working strokes of the pistons is the highest.

Besides ovality, side forces also cause taper. As the piston moves down, the effect of lateral forces decreases.

Seizures on the cylinder walls are formed due to overheating, oil starvation, oil contamination, insufficient clearances between the cylinder walls and the piston, poorly fixed piston pins, due to breakage of the piston rings. How much cylinder wear can be determined using an indicator or a bore gauge.

How to measure wear correctly?

Ovality or ellipse should be measured at a belt that is located 40-50 mm below the top of the combustion chamber. You need to measure in planes that are mutually perpendicular. Wear will be minimal along the axis of the crankshaft, and maximum - in the plane that is perpendicular to the axis of the crankshaft. If there is a size difference, then this will be the ovality value.

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 difference in size in the indicator readings, then this is the size of the taper. In this case, it is necessary to measure the lower and upper part of the cylinder. The indicator is lowered strictly vertically so that it does not deviate to either side.

If the size of the ellipse 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 needs to be repaired.

Under the 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,bore and then finish, install sleeves.

BTS grinding

This operation is performed mainly on internal grinding machines. The stone on this equipment has a much smaller diameter than the size of the cylinder. The stone can move around the axis, along the circumference of the cylinder, and also along the axis of the combustion chamber.

The process of repairing the engine block, thus carried out, 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 can become clogged with dust. The latter penetrates into the pores in the cast iron - after repair in the future, this can cause intense wear of the rings and pistons. Cylinder grinding is now extremely rare.

Boring

Repair of cast-iron engine blocks can also be done in this way. Use boring stationary and mobile machines. Mobile vertical boring units are fixed in the process directly to the block. At the same time, 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, the spindle is carefully centered using cams. The cutter is adjusted to the required size using a micrometer or inside gauge.

The downside of boring is the need for subsequent finishing - on the surface without finishing there are traces of the cutting tool. Fine-tuning during the repair of the cylinder block of a diesel engine, gasoline units is performed inspecial or drilling machines. In simpler cases, you can get by with an electric drill and a finishing head with abrasive stones. In the process of any finishing, the processed cylinder is abundantly poured with kerosene.

At the end of processing, the taper, as well as the ellipse, should not be more than 0.02 mm. Diamond boring is performed with carbide cutters at low feeds and high speeds. It is better to work on special boring machines.

Sleeving

This engine block repair technology is selected when the cylinder wear is greater than the last repair size. Also, sleeves are chosen if there are very deep scratches and risks on the surface.

The cylinder must be bored to a diameter that will allow 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 groove for the collar for the sleeve.

The sleeve is made from materials that are close in properties to the material of the cylinders. The outside diameter must have a press fit allowance. The sleeve, as well as the walls of the cylinder, are lubricated with oil and pressed in with a hydraulic press. If a press is not available, the sleeves can be installed using a hand tool.

Valve seat repair

Along with the BC, it may be necessary to repair the engine cylinder head. If the wear of the valve seats is small, then this can be eliminated by simply lapping the valve against the seat. If the wear is significant, then the seat is milled with a taper cutter. First thingprocessed with a rough cutter with an angle of 45 degrees. Next, choose a cutter with an angle of 75 degrees. After taking the part at an angle of 15 degrees. The seat can then be machined with a fine cutter.

Milling will only be effective if the valve guides have minimal or new wear.

In the process of repairing the cylinder block 406 of the engine after milling, the seat is ground with cone stones with a drill and the valve is lapped. If the wear of the seats is large, then the seat must be bored on the machine with end mills and a cast-iron ring is pressed in there, which then must be machined in the above sequence.

If it is possible to replace a replacement seat, then to facilitate the repair of the cylinder head of the 406 engine, simply change the old seat to a new one.

Valve bushing repair

If the valve guides are worn, then they can be restored by reaming a long reamer to the repair size. If the wear of the bushing is significant, then they should be removed under pressure and replaced with new ones. When pressing new bushings, the interference should be 0.03 m. Then the diameter of the bushing is expanded to the nominal size.

Repair of tappet guides

These elements, made in a block in separate parts during the repair of the cylinder head of the 402 engine, are processed by reaming to the repair dimensions of the push rod or by replacing the push rods.

Conclusion

As you can see, it is impossible to overhaul an engine 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 heads.