Buying a car with mileage is a very responsible procedure, as it provides for a large number of legal and technical inspections. As for technology, ie analysis of the condition of the vehicle itself, when buying a used car maximum attention should be paid to the most expensive items: body, engine, transmission, individual components of the chassis and steering.
We also recommend reading the article about it, how to start the engine, if the car stood for a long time. In this article you will learn about the basic requirements and recommendations for successful engine start after a long downtime.
If the condition of the body can be assessed visually, and the serviceability of the chassis is easy to check on the lift and test on the road, then with the engine to solve the problem is not so simple. Usually, the seller will not allow you to open the motor for diagnostics. Similar difficulties arise in that case, when it is necessary to check the removed engine when buying a contract power unit.
In this article, we intend to talk about it, how to check the condition of the engine when buying a car on gasoline, and what methods help to check the diesel engine when buying a car.
Check the used engine before buying
Let's start with that, that much about the state of the engine can be learned by visual inspection of the engine and bonnet space. First of all, should be remembered, externally clean engine, which starts and works, does not mean yet, that the motor is fully functional and in good condition.
Experienced masters at the service station are well aware of this, also familiar with this car dealers and not quite honest sellers. For this reason, you need to know clearly when assessing the condition of the used internal combustion engine, what to look for.
so, let's deal with that, how to check the engine when buying. First of all, even if you do not have much experience, it is not necessary to tell the car dealer about it. Try to refrain from any unnecessary comments, follow the step-by-step instructions, which we will discuss below.
- Before you start inspecting the engine, start with simple questions about repairing and maintaining the car and engine. Ask, what and when was done on the engine, at what mileage the engine oil was last changed, when replacing belts and rollers or timing chain, antifreeze, spark plugs, etc.. P.
- Also ask about the type and brand of oil poured (example, synthetics, semisynthetics, 5W30 or 10W40) and other technical fluids. In parallel, observe the clarity and transparency of the answers and the reaction of the owner.
This approach will immediately identify or reseller, who does not know the history of the car, or a careless owner, who did not pay proper and timely attention to the car.
Visual inspection of the engine
Then you can proceed to the review of the engine. If the seller prohibits or knowingly complicates access to individual external elements under the hood, then it is better to refuse purchase of such car at once. In that case, if no problems occur, you can continue.
As we have said, first, what you need to pay attention to, these are traces of engine oil. Oil stains or traces of antifreeze will indicate a leak through the gaskets, seals and other seals. In some cases, such problems can be solved without significant financial investment, while in others the oil can be squeezed out as a result of serious engine malfunctions.
We also recommend reading the article about it, why the oil "drives" through the engine breather. In this article you will learn about the methods of diagnosis and various causes of this phenomenon.
It turns out, a worn gasket or seal may leak, which is not so difficult to change. However, in some cases, similar leaks can occur for other reasons. Example, when the engine was overheated, The cylinder head can then "tell", that is geometry of a privalochny plane is broken. As a result, replacing the gasket will not solve the problem.
Let's add, that even if nothing serious happened to the engine, dirty engine with stains will indicate that, that the owner for any reason does not pay due attention to the condition of the vehicle, carelessly operates the car, etc.. P. That says it all, that the rules of maintenance, oil changes and consumables could be systematically violated, which is very bad for the resource of the unit.
The flip side of the coin can be considered and recently washed, completely clean engine. Usually, washing the hood space is done in two cases:
- in order to give the overall appearance of the car;
- to hide oil and technical fluid leaks;
Unfortunately, the second case is much more common, since a serviceable motor is rarely washed before sale. Moreover, sellers separately sharpen the buyer's attention to that, that the engine is dusty and the engine is not specifically washed, that is, clearly visible, that there are no leaks.
Anyhow, detection of stains is a cause for concern and / or bargaining. A clean engine should also alert, which requires closer scrutiny. The engine can be considered the best option, which is covered with a small layer of old dust, at the same time has no stains.
Check the condition of oil and antifreeze
If you don't know, how to check the diesel engine when buying or you are interested in checking the gasoline unit, then it is necessary to begin with an estimation of a condition of technical working liquids in internal combustion engines. We are talking about engine oil and coolant cooling system.
- Let's start with butter. The first thing you need to unscrew the oil filler cap. Ideally, the lid itself should be without traces of obvious oiling on the outside, the inner surface should also not be dirty, with traces of oil foam, etc.. P. The latter statement is also true of the walls of the neck.
- Next, you can get an oil dipstick and assess the condition of the oil. If it is fresh, transparent, has no impurities and foam, then it will be difficult to identify anything quickly. Black oil says so, that or oil has not changed for a long time, or the oil turns black quickly as a result of general engine and contamination.
That should be especially alarming, that the oil in the engine may foam, that is, an emulsion is formed on the lid of the oil filler neck and / or on the probe. In this case, it becomes obvious, that liquid from the cooling system enters the lubrication system. Note, that in this case or immediately bargain with the seller the cost of a similar contract engine / overhaul, or discontinue further examination.
As for checking the engine for cooling, the task comes down to that, to determine the breakthrough of gases and their entry into the specified system, as well as to detect the possible appearance of traces of oil in the coolant. For diagnostics it is enough to open a cover of an expansion tank. If traces of oil are visible, there is a revival of the coolant in the tank on the running engine, then the problem is obvious.
In some cases, the culprit may be a punctured cylinder head gasket, whereas in others the possibility of hidden cracks in the BC or cylinder head should not be ruled out.
Diagnosis of the state of the engine by spark plugs
Checking the spark plugs allows you to identify a number of potential malfunctions of the engine and its systems.
You should pay attention to such things, as:
- oiling;
- black, red or white soot;
- traces of unburned fuel;
The above and other signs are a clear indicator of certain problems. It is worth considering, as checking the engine for color and soot by the condition of the spark plugs is an effective method only subject to certain conditions, recommend reading about such diagnostics and nuances in our separate article.
Extraneous sounds and engine vibration
Evaluation of engine performance at the initial stage involves the detection of extraneous sounds, triplets, omissions of ignition and ignition of the mixture, as well as other failures in the internal combustion engine.
- After, how the engine worked, you need to listen to his work, and look at the level of shaking and vibration. If there is such an opportunity, you can use a stethoscope, which will allow you to listen to hidden defects and localize suspicious noises.
Let's note at once, that knocks of different tones and frequencies, and uneven work indicates problems. If the gasoline engine runs like a diesel, when you press on the gas there are failures, the unit shakes a lot, etc.. P., then obvious faults.
- Different systems can fail (inflammation, food), and individual nodes inside the engine. The crankshaft can knock, pistons, abo valve hydraulic lifters, connecting rods, etc.. d. Shaking and vibration are the result and sign of breakdowns, however, the possibility of engine cushion problems should not be ruled out.
To study in more detail the problem of extraneous knocks and noises, we recommend reading our separate article on the topic of knocking in the engine. As for vibrations, we also offer you detailed material for acquaintance.
Exhaust color analysis during engine inspection
Exhaust color and intensity, as well as the composition of the exhaust gases in many cases clearly indicates the presence or absence of problems with the engine and its systems.
Let's start with that, that on the serviceable warmed-up injector engine in a warm season any smoke practically is not visible. There is also no smell of exhaust. In the case of the carburetor, you can sometimes see a slight grayish-white smoke, the smell is clearly present.
In the cold season, only white smoke is allowed to warm up, looks like a couple. In other cases, black, blue or blue smoke indicates a malfunction of the internal combustion engine, ignition systems, power, etc.. P. Constantly thick white smoke is considered to be especially dangerous, which indicates that the PR enters the combustion chamber.
Oily blue smoke is a sign of oil consumption, wear of piston rings and CNG. Black smoke indicates strong coking, problems of mixture formation and combustion of fuel-air mixture.
We recommend that you read the article about it, as indicated by blue, siziy, white, black and other shades of engine exhaust. You will learn from this article, how to check the diesel engine when buying a car or detect a malfunction in the color of the exhaust on a gasoline car.
Check the engine while driving
so, if the engine runs smoothly, do not dim, does not knock or vibrate at idle, and responds quickly and clearly to the accelerator pedal, then you can make a test trip.
Let's make a reservation at once, short-term driving will not be enough. It is important to evaluate the operation of the unit in different modes, and warm up the engine to operating temperatures. For this reason, you should count on a distance of at least 10-15 km.
To solve the problem, you should offer the car dealer reasonable compensation for fuel and time spent. Next you need to ask the owner, who will be with you in the car, do not make noise. You also need to turn off the speaker system, to be able to listen to all extraneous sounds.
- First of all, look at the dashboard, does not light up or periodically "check" the engine. In parallel, evaluate the sound of the motor when accelerating, during engine braking, at sharp acceleration, etc.. d. Also while driving you can listen to the engine alternately with open and closed driver's and / or passenger window.
Pay attention to jerks while moving, vibration, knocking and whistling. If nothing like this is found, then at the end of the trip immediately open the hood and assess the external condition of the heated engine. The presence of fresh stains on a clean engine will indicate problems, which the seller wanted to hide, pre-washed under the hood space
- Check the oil level and condition again, also allow the unit to cool slightly and look into the expansion tank, assess the condition and appearance of the coolant. Smoke should not come out of the tank, there should be no oil stains on the surface of the antifreeze.
- If the situation allows, you can unscrew the candles again and re-evaluate their condition. In some cases, it is possible to agree with the owner and even measure the compression (if the buyer has a compressor).
Tips
As you can see, superficial inspection and inspection of the engine before purchase allows you to detect a large number of hidden defects with the right approach. If you are not confident in your abilities, then the correct decision will be the order of complex diagnostics of the power unit and all car on HUNDRED. Specialists will perform computer diagnostics, indicate the presence of possible problems and immediately announce the approximate cost of repairs.
In the future, the information obtained can be used as a good reason to refuse to buy or reasoned bidding. Finally, let's add, that it is useful to have a compact diagnostic scanner-adapter in the OBD2 diagnostic connector for fast diagnostics of cars with ECM. The device allows you to quickly scan the system for errors, and evaluate the operation of engine systems in real time.