How to check an engine removed from a car

The engine is the main part in a car. This is the heart of the car, which, in fact, makes it go. The engine is expensive. Even contract engines for budget cars can cost hundreds of thousands of rubles, which sometimes exceeds the cost of the used car itself.

The price of the engine is at least 70 percent of the cost of the car, so checking the car's engine is the main step before buying a used car. The check is performed in several ways, and you can find out not only about the condition of the engine, but also its number. With the help of technology it is easy to calculate even the real power of the unit.

There are a number of ways to check the engine of a car before purchasing, and today we will look at them in detail.

Self check

A method for those who understand cars and can determine the condition of the engine themselves. If you decide to check the car engine yourself, then start by opening the hood of the car.

When checking yourself you need:

Inspect the engine itself for leaks, foreign liquids and deformation of the housing from impact. After this, the presence or absence of some common problems, such as damage from external impact (frontal impact) or oil leaks, will become obvious. If the engine under the hood of a used car is dusty and dirty, then you are in luck: a clean and washed engine does not show any leaks of oil or other liquids. You should inspect the engine for leaks during daylight hours and with a flashlight, in other words, with maximum illumination of the engine compartment. If the engine has recently been washed, then all that remains is to ask a question about oil leaks, counting on the seller’s honesty, otherwise such a defect will be identified over time after purchasing the car, and this will become an unpleasant surprise.

While you are near the running car, you can check the sound of the car's engine. It should operate smoothly, without changes in sound and without making the sound louder or quieter without pressing the pedals. It is worth remembering that the sound of a diesel engine is different from the sound of a gasoline engine - it “rumbles” like a tractor, while a gasoline engine operates in the same key. The sound of boxer engines, which are found on some sports cars, for example, on the entire Subaru line, is also different - these engines “growl” even at idle.
Take a ride in a car. In fact, the only way to see the engine “in action” is the ability to independently evaluate the power and response to the pedal, to understand whether everything is working as it should, and whether the car is losing power, whether there are any “dips” when driving, and so on.
Inspect the engine compartment and find out if the car has had a frontal impact. If you can see that the front end of the car has been recovering from a severe accident, it is worth considering that this may affect the performance of the engine in the future.
Connect the diagnostic wire - if you have such equipment, you can read the error logs of the on-board computer and find out for sure what problems the engine has. But be careful – sometimes unscrupulous sellers use technology to erase errors from the computer’s memory.

If you have a diagnostic wire and you are checking a foreign car that is not too old, then connect a laptop through it and read the errors recorded by the on-board computer. In modern cars, the computer reads errors and saves them in a log, which can always be viewed using the appropriate equipment, which is simple and inexpensive: you only need an OBD cable, a laptop and software for your car brand.

If you are unlucky and come across a “dead” car, the computer will generate a bunch of errors, including engine errors. Next, you simply compare the error numbers with the database and get information about what exactly is wrong, and there can be a huge variety of different defects: from malfunctioning engine mounts, leading to vibrations in the cabin, to missing ignition coils or scuffing in the cylinders.

Why do you need a major engine overhaul?

Major engine repairs are usually done due to damage to the cylinder walls. Modern engines do not tolerate overheating and heavy loads immediately after a cold start. They are also sensitive to knocking effects when driving on low octane fuel. As a result, already by 150 thousand km on expensive premium cars, blue smoke may come out of the exhaust pipe, indicating the appearance of scuffing.

Due to detonations, pistons scratch the high-strength coating and break off its fragments. Oil enters the cylinders through the formed shells, and after combustion it is released into the exhaust pipe, coloring the gases dark.

Checking at a car service center

A surefire way to learn everything about a car and its engine if you don't consider yourself a good expert to inspect it yourself. For a reasonable fee, service specialists will inspect the car completely, consider it a computer (if the car has a diagnostic connector), check all the technical components of the car and even find out whether there has been interference in the memory of the on-board computer, whether the mileage has been changed through it and whether errors have been erased.

It is better to contact either official dealers or specialized centers that work with one brand of car, or with a narrow range of car brands. As a rule, such services know better all the typical “sores” of cars and are very well versed in the engines presented on the brand’s models.

In this case, you only need to choose a service that has a large number of positive reviews and a long history of work, pay for the service and wait until the diagnostics are completed, after which you will be given a work order. Whether you buy a car after that and pay for spare parts and repairs, or hand over the document to the seller and refuse to buy the car, is up to you. This method of checking a car engine is very effective and, as a rule, error-free - if the car is faulty or requires significant investment, specialists will report this based on the diagnostic results.

Advantages of using a car service:

You will know for sure all the ins and outs of the car and its components: they will tell you whether the car’s mileage was low, whether there were any accidents, what exactly needs to be replaced or repaired at a given time, etc.
They will issue an order on the spot and tell you where to purchase spare parts and consumables. If you purchase a car right on the spot, you can begin to work on fixing problems without going anywhere.

Disadvantages of working with a car dealership:

It is necessary to pay for the services of a specialized service; prices vary depending on the region and the qualifications of the servicemen. On average, for services specializing in foreign cars, one standard hour is estimated at 900 to 2000 rubles, diagnostics last an hour and a half, these costs are borne by the potential buyer.
You will have to spend time on the road to the service, diagnosing the car and then on the way home, you also need to agree on a time that is convenient for all parties: you, the seller and the car service center. Due to the complexity of the organization, the process can take weeks.
If you choose an inexpensive service “behind garages,” there is a risk that the diagnostics will not be carried out efficiently, which will result in additional expenses for you after purchasing the car.

On-site vehicle diagnostics

The service has come into use recently, but has managed to spread widely and attract a huge number of specialists. Today, anyone can order a car inspection at home; it’s practically the same as a car service, only specialists come to you, and not you to them.

As a rule, the inspection is carried out by automobile experts who work either as mechanics in a car service center or as specialists in the sale of used cars. With a trained eye, they will determine the condition of the car, conduct diagnostics through the on-board computer and tell you exactly what this car has experienced in the past, and what you should be wary of in the future.

The advantage over the service is that you do not need to go anywhere, and the check will be carried out faster, however, the weakness of field specialists remains the lack of complex equipment present in car services, such as a lift. However, if you have a garage with a pit, this problem is leveled out.

Specialists will come to you with a set of necessary equipment and inspect the car. The work takes from 40 minutes to one hour.
As a rule, on-site diagnostic specialists have carried out a similar procedure many times already, and with a trained eye they can quickly and accurately determine what exactly is wrong with the car. The quality of diagnostics and the “verdict” of field experts are usually very accurate.
Experts in car selection also negotiate with the seller for you, and you can “bring down” the price of a car you are interested in in good condition. Despite the fact that the price for such services is high, it is usually less than the amount that car selectors manage to negotiate for, and as a result, everyone benefits.

Lack of some professional equipment present in the car service.
There is a risk of encountering amateurs who incorrectly assess the condition of the car.

How to check car engine power

If you buy a powerful car with a lot of “horses”, it is probably important for you to know whether the engine has lost its potential over the years.

For such a check, it is necessary to drive the car to a power stand, a special device on which the engine is subjected to maximum load and they find out how much horsepower and torque the unit actually has.

Over the years, cars lose their former properties, engines weaken and lose horsepower, and only with the help of a power stand can you find out how many of them are left, and only then decide whether it is worth buying a car that has lost its former strength over time.

It doesn’t matter whether you check the car yourself or take it to a service center, you can always find out the most basic things about the car’s engine thanks to the Autocode online service. The free report based on the results of the inspection will indicate the type of engine, its power and volume, so you can calculate the tax on this car in advance and estimate fuel consumption.

By ordering a full report for 349 rubles, you will find out the entire history of the car: actual mileage, presence of traffic police restrictions, customs history, history of fines, information about compulsory motor liability insurance and those. inspections and much more.

Before buying a car, with or without checking its technical condition, it is always better to have a report on it. With its help, you can avoid significant losses and not face deception from the car seller.

If after receiving the report you are unable to travel for inspection, use an on-site inspection. The technician will arrive on site and diagnose the car using special instruments. Just order an Autocode on-site inspection and be confident in your purchase.

Replacing a power unit in Russia used to be almost impossible. So many documents had to be collected that the whole point of the procedure was lost. In the process of processing such a replacement, the owner had to visit all police departments and pay a lot of official and unofficial fees. Today the situation has changed for the better. This does not mean that nothing needs to be done to register a new acquisition, but the complexity and duration of these activities has been significantly reduced. Today we will not discuss the issue of documents and procedures for replacing an old motor with a new one. Much has already been said about this, everything has been sorted out. Let's talk better about the hardware part of the process. How to choose a good used engine and make sure of its quality? This is a complex procedure that requires the buyer to be extremely careful and not rush.

It's one thing when the engine is installed on a car. It is enough to take a ride in the car and listen to the operation of the unit in different modes. But when you select a motor that has already been dismantled, it is almost impossible to check it. You are buying a metal product that has been used in another car for many years. Now it is important to assess the condition of the engine, look at the main features of its technology, and make sure that the engine is working and will not let you down in the near future. Of course, when replacing an engine, it is best to buy a new product and get a warranty. But this is not always possible from a financial point of view. Today we will touch on the topic of checking and choosing a used engine at a disassembly site or in another specialized company. There is no need to check new motors. It is enough for them to be installed by an official dealer, who will confirm the warranty and issue all the necessary documents for the unit.

Why do a single-phase motor have two windings?

All electric motors discussed today have low power. The magnetic core of a single-phase machine contains a winding of two phases, this is the main (working) and starting. The latter does not take part in the direct operation of the engine.

Such a pair of windings is needed to make the rotor of a single-phase motor rotate. The most popular of these drives are divided into two subtypes: electric motors with a starting winding and those that contain a run capacitor in their design.

In the first case, so to speak, the non-working winding will be turned on through the capacitor when the motor is started, and when the unit returns to normal operation (the rotation speed becomes constant), it will turn off by itself. The drive will continue to operate with one working winding. Information about the capacitor is usually indicated on a special plate on the motor housing. Its characteristics directly depend on the design.

Single-phase asynchronous motors containing a run capacitor always operate with the auxiliary winding switched on. It is turned on through this same capacitor. The capacity of such a capacitor also depends on its design features.

In other words, a motor with a starting winding is characterized by its turning off after starting. But with a capacitor auxiliary winding - its constant operation, because switching occurs through a constantly operating (even while the drive is running) capacitor.

To properly test the performance of a single-phase motor, knowledge of the design of its windings is critical. The differences between them can be found in the cross-sections of the wires, the number of turns, the resistance value of each of them (they can be measured with different types of testers or using an ohmmeter).

Where to buy a used motor is an important question

There are three main places to look for a used deal. It is very important to choose the right source so as not to get into trouble with the device in the future, including its documentation. Other verification factors also depend on the choice of acquisition method. Sometimes it is enough to visually inspect the unit, but in many cases it is better to test it. When purchasing a used power plant for a car, you should pay attention to the following sources of information about the products sold:

Advertisement sites. Here you can easily find private advertisements for the sale of engines removed from other cars. Focus on offers from private individuals, it is easier to get a discount and honest information here.
Showdown. In such companies you can always find a motor with the required characteristics and get quite adequate equipment. Do not forget to compare the cost of units at different disassemblies.
Contract motors. A very important area is the delivery of contract engines to Russia. These are units with low mileage that were removed from cars in Japan, Europe or the USA, and then sold in the Russian Federation.
Automotive stores. Many large companies sell used units. Their advantage is that they often test the motor before selling it and give a small guarantee.

Visual inspection of a used engine – what to look for?

Used motors look pretty similar to a layman. One may be dirty and the other clean. The price tag often contains information about mileage, which is almost never true. It is especially surprising when at a showdown they offer the engine of a popular car model with a mileage of 70-80 thousand km. Cars often end up being dismantled after 500,000 km. This is worth remembering. Visually you can evaluate the following points in technology:

condition of the housing - here we are not talking about cleanliness, but about the presence of various types of damage, especially in the engine crankcase area, which can indicate problems with the internal combustion engine;
appearance of the peripherals - look at attachments, wires, terminals, plastic covers, as it is easier to determine age and mileage by their appearance;
dipstick and oil filler cap - if used carelessly, these parts become loose and untidy, and a new dipstick should also make you a little wary and raise questions when purchasing;
timing belt - if you buy a motor with a mileage of 130,000 km, and the belt on the motor is completely worn out, it means that the engine has not been worked on, or the mileage was indicated to you incorrectly;
bolts on the body - if there are traces of unscrewing, then they were introduced into the engine with an attempt at repair, this is not the best option to purchase, it is better to check it more carefully.

These checking features do not provide unambiguous information, but they help to better understand which unit is in front of you. This is important for the overall assessment of the offer and will also help you negotiate with the seller. You always need to bargain for used units, unless you are talking about buying a contract motor. Most likely, at the visual inspection stage you will be able to understand whether it is worth continuing to study this proposal. This is an important, but not the most valuable process.

Typical design of electric motors

The design of electric motors is the same for all classifications. Power mechanisms are equipped with a stationary element - a stator, and a rotating element - a rotor, and in some types - an armature. The formation of a circular motion of the rotor occurs by the influence of the magnetic field of the stationary component on the rotating element (RE).

Electric currents flow in the stator windings. If the windings are in good condition, then the rated design currents pass through them. The latter create a magnetic field of the most optimal magnitude. A breakdown provokes a deterioration in the resistance of the conductors, which leads to the creation of a short circuit, interturn short circuit, and leakage currents. All of the above negatively affects the functionality of the device.

A minimum gap is provided between the static and rotating elements, separating the parts of the commutator motor (CM). It is violated:

broken or worn bearings;
abrasive and mechanical particles that got inside;
manufacturing defects, improper maintenance followed by poor quality assembly.

The contact of the stator and rotor triggers destructive processes - additional mechanical wear is formed. This complicates the diagnosis and repair of electrical installations with collector units. This also includes an attempt to disassemble the assembly of units using “makeshift” tools. For maintenance, it is necessary to use special equipment to prevent damage to the shaft faces.

After disassembly, play and free movement of bearings are checked - their cleanliness, amount of lubricant, and fit. Due to the special design of the motor, the plates and brushes are additionally checked - parts may be heavily worn, which affects the performance of the motor equipped with a commutator unit.

Technical check of a used or contract motor

There are not many technicians that can help carry out a technical check of an engine that is not installed on a car. In this case, there is no way to start the engine, check its operation, or listen to sounds. But you can also visually evaluate many technical aspects. By the way, at this stage you can check whether the unit has been removed from the drowned car. To do this, you need to look for rust or even the remains of small algae in places where there can be no corrosion.

Technical assessment of the motor involves the following procedures:

unscrew the spark plugs - each spark plug should have the same pattern - brown carbon deposits at the end; if the spark plugs are new, be sure to find out the reason for their installation on this unit;
look at the timing belt manufacturers (the original is best, ContiTech, Gates), the oil filter brand (Mann or Knecht), the spark plug brand (Bosch, NGK and other well-known brands);
Using a micrometer, you can measure crankshaft lateral play in a few minutes - read more about this procedure if you know how to perform this task;
measuring compression in the cylinders is possible with the engine removed, and it is also advisable to do this, but you should not rely on these indicators, especially if the unit has been sitting for a long time;
It is advisable to remove the manifold and look at the condition of the valve system - on V6 engines from Europe there may be a small amount of carbon deposits, but on other units there should not be any.

These are the difficult features of technical testing that should be taken into account when purchasing a contract or simply used unit. More detailed information can be obtained by specifying the specific model. Diesel power plants have their own important testing rules; for powerful or exclusive technical units, you can find expensive special diagnostic equipment. Sometimes an inspection may not cost much less than the product itself.

The winding has broken

There is nothing surprising about a winding break; this is the most common malfunction in the operation of electric drives. A breakdown can occur in both the stator and the armature.

If one phase in the winding breaks, then there will be no current in this place, but in the second phase the current indicator will be overestimated. This can be measured using the same multimeter in ammeter mode.

In general, this failure is equivalent to a loss of phase. For example, if a break suddenly occurred while the drive was in operation, the engine begins to sharply lose power and overheat. If the protection on the unit is working correctly, it will turn off. Solving the problem basically requires rewinding.

In a situation where a break has occurred in the rotor, the frequency of current oscillation will be equal to the frequency of voltage oscillation and slip. External signs: strong buzzing and vibration, decreased drive speed.

All these are just causes of breakdowns, but they can only be detected if you ring each winding of the electric motor and measure their resistance.

The starting and working windings are connected in those single-phase motors that operate at an alternating voltage of 220 V. The starting winding must produce a resistance that is 150% greater than that of the working winding.

To quickly check the performance of the electric motor, you can also use a function on the multimeter called “Dialing”. If the circuit is working properly, you will hear the characteristic sound of the device, and in some models there is also a light indicator. But if there is a break in the circuit, you will not hear any sound.

Installation and first days of operation of a used engine

Installation of the unit is quite simple. If you have chosen the engine of exactly the desired model, it is enough to dismantle the old installation and install a new one. After this, it is important not just to go on a trip along the roads of Russia, but to check all the functions and capabilities of the engine. Only in this case can you finally be sure that you have purchased the appropriate power unit option. Basic testing immediately after installation consists of the following features:

prepare the engine for operation - replace spark plugs, filters, oil and belts to ensure that your car is safe to drive, no matter what conditions you drive it in;
warm up the equipment well, look at the operating temperature and start moving very smoothly and slowly, only after a few kilometers can you increase the speed;
after a good warm-up, stop, open the hood and listen carefully to the operation of the unit, this will help you quickly identify possible problems on the first day of operation;
then get back in the car, find a fairly long straight with good asphalt, go to gear 3 on the manual or lock the gear on the automatic and accelerate;
A few minutes of driving at high speeds will give you a full understanding of possible engine problems, but be careful - with large problems this can lead to instant failure.

There are dozens of unit testing methods that can help you get the results you want. You can pay a lot of money to specialists, or you can carry out all the necessary procedures yourself. But be extremely careful, as one wrong move can easily ruin the engine and cause big problems in the future. Interestingly, a self-test perfectly demonstrates all the troubles of the node.

We invite you to watch the video and get more information about checking an engine that has not yet been installed on a car:

Three phase motor

There are 6 terminals on the body of a three-phase motor, all of them are responsible for the beginning and end of a specific winding. However, they are all the same. This makes the case of breakdown the most difficult.

Working with a multimeter is as follows:

the device in resistance measurement mode determines those pairs of terminals that are responsible for one winding;

The resistance of each is accurately measured and then compared. If there is no difference in the measurements, the windings are working properly and there are no interturn short circuits.

Let's sum it up

We can talk for a long time about the fact that replacing the engine is not an ideal solution to the problem. But sometimes situations develop in such a way that this is the only way to continue operating the vehicle. It's worth considering this option if the cost of repairing your engine proves to be prohibitive. In this case, it is worth choosing a used unit, even if it is a contract motor or a unit removed from a car in Russia for disassembly. Sometimes, when checking, you can make sure that you are buying a quality unit. But in most cases, the main testing will be done after installation.

There is no perfect option for purchasing a used powertrain. There are only recommendations for each case, but not a specific way to buy a guaranteed good engine. To a greater extent, contract engines are installed on cars. These are engines from another country that have not been driven too much; they are often removed from cars after an accident. But this is not a panacea, since contract units are often damaged internally. Therefore, when purchasing, always agree on a possible return or exchange of the purchased equipment. What do you think about installing a used engine in a car?