Often, in numerous forums devoted to automotive topics, you can read topics about knocks in the engine or cranked liners. This is an emergency in the engine. When they say that the liner has cranked , it means that the sliding bearings on the crankshaft and on the connecting rods have pulled out of the seat and they have become unusable. This is a serious failure, which happens quite often. Car enthusiasts see the reason in low-quality motor oils from an unknown manufacturer.
But there are much more reasons, and they are not directly related to the lubricant and its quality. As evidence of this, there are many examples when indigenous liners fail if brand-name original oil is poured into the engine. Or vice versa - bearings operate more than one hundred thousand kilometers on medium-quality oils. Let's see why crankshaft liners rotate, what factors affect this and what is the main reason for this phenomenon.
Connecting rod bearing - what is it?
In the internal combustion engine there is one very heavily loaded part. This is a crankshaft. The element is not mounted on traditional bearings. Due to the design features, plain bearings are used. The design of these very details may be different. But the constant improvement of engines has led to the fact that now a steel sheet is used, coated with a special antifriction layer.
This is the
connecting rod bearing. These elements are installed in special places - beds. The liners are fixed. The need to fix these parts is due to the fact that they have holes for oil movement. They must be consistent with those in the beds. Also, by means of fixation, friction is provided on special surfaces intended for this purpose. The connecting rod bush is a kind of protective element, due to which the life of the crankshaft is significantly increased.
The difference between the main and connecting rod bearings
You need to know that there are two types of inserts. These are cranked and radical. The first are between the connecting rod and the neck of the crankshaft. The root element is similar to the first in its purpose. However, it is located where the crankshaft passes in the engine housing. Inserts vary in size. Dimensions depend on the type of ICE for which a particular part is manufactured. There are special repair liners. They differ from the original new ones installed in the engine. Repair liners differ only in multiples of 0.25 mm. So, their sizes are approximately the same - 0.25 mm, 0.5 mm, 0.75 mm, 1 mm.
Reasons for turning the liners
So, the crankshaft is a part that works in harsh conditions, and it has to withstand enormous loads in extreme temperatures. In order for the mechanism to be held firmly on the axis and to ensure the correct operation of the entire crank mechanism, inserts are needed. The shafts on the shaft work as an inner ring. Inserts - as external.
In the engine block there are channels for supplying lubricant under pressure. Due to the oil film that envelops the liners, the crankshaft can rotate. Why do car owners face situations when crankshaft liners are cranked in the engine? There are several possible reasons. Let's look at them below.
Mechanical wear
The first reason that when replacing the engine, replace the main and connecting rod bearings, is the development. Parts wear out due to mechanical stress. Many try to save the loose leaves, however it is useless. Physics is involved here, and physical processes cannot work differently. Depreciation is inevitable. The antifriction layer on the liner erases over time. This leads to crankshaft free play. Backlash appears. As a result, the oil pressure decreases, and quite significantly. On most engines that are highly reliable, if the liner is cranked, this indicates their wear.
Crank crankshaft connecting rod
This is also one of the most common faults. This problem faced a lot of car owners. But not everyone knows about the reasons. Let’s figure out what happens to the element. The connecting rod bush plate is quite thin.
It is installed on a special seat. The outer walls on the half rings have special protrusions, which, even in the non-rolled and undeveloped engine, abut against the front of the cylinder block. At some point, the seat simply cannot hold the connecting rod bearing. As a result, a typical situation - cranked liner. The plate does not just rotate, but also sticks to the neck of the crankshaft. In this case, the motor stalls and will no longer start.
Causes of damage to the connecting rod bearings
Specialists in the repair of internal combustion engines see several reasons why plain bearings rotate. Often this is due to excessively thick oil, into which particles of metal fall. Grease with chips has an abrasive effect on the liners. Often there is a complete lack of oil. Especially this affects cars with worn oil scraper rings. Part of the grease just goes "into the pipe." As a result, the liner cranked and the engine goes for repair. Bearing caps may not be tightened together enough. And finally, another reason. This is too liquid oil. Especially such products are harmful to motors operating under high loads.
Interference violation
If cranked liners, there may be reasons for this. In production cars assembled at the factory by qualified specialists, this will not happen. But if the motor has already been repaired, then, most likely, the selection of liners was performed incorrectly and the interference was violated.
When the engine is running, the liners experience increased friction. This moment seeks to crank the liner. And due to the reduced force that holds the part in place, the risk of turning increases at times. Under the influence of uneven loading, a weak fit of the friction bearing causes the liner to vibrate. The lubricating film is also broken. As a result, the part is rotated, and the retaining sill is not able to prevent this.
How to identify a breakdown
When cranking the main liners , the crankshaft and cylinder block immediately fail. In the case of cranking rod bearings, the connecting rod itself will go out of order, it will roll, and also the cylinder block. As a result, only a complete overhaul of the motor can help the car owner. This failure can be determined. There are some signs of cranked liners. One of them is a characteristic metal knock on the entire motor.
It does not stop even at idle, and with an increase in load it knocks even more intensively. Another sign is low oil pressure. If the engine is cold, then there may be no sounds. If the situation is hopeless, the motor will stall, and it can only be revived by repair.
Repair and consequences
A typical situation - cranked liners. What to do? The problem can be solved in different ways, depending on the nature of the damage. In some cases, you can do without replacing the liners with grinding the crankshaft. In difficult situations, repairs will be much more expensive.
If the connecting rod bush is turned, then in modern engines this is not a serious problem. But this does not apply to the root. Often a situation occurs that a damaged liner simply changes, and the motor runs on. Experts do not recommend this approach. The resource of the connecting rod-neck of the crankshaft restored in this way can be greatly reduced. A much more acceptable option is to replace the connecting rod with which the problem has occurred. Also, if cranked liners (VAZ-2172 including), the lock on the connecting rod will also break. It will be more optimal to bore the crankshaft to the next repair size and perform a complete replacement of the liners and connecting rods.
Grinding the shaft after turning is necessary.
Badges form on the neck of the mechanism. This is the only way to achieve the desired surface condition and the engine will work correctly.
What is the result
If something rattles in the engine, then this is a signal for the immediate termination of the vehicle. Do not start the engine. Most likely, inside the engine cranked liners. Repairing this damage can be quite expensive. It should be noted that the temperature conditions of the motor also affect the resource of the elements. Do not overheat the engine. As for oil, it is safest to use those products that fully comply with the requirements and tolerances of the manufacturer.
Conclusion
So, we found out for what reasons the crankshaft liners are turned. To prevent damage, do not keep the engine for a long time at high speeds, change oil, filters in time and observe the temperature conditions of the motor.