Checking the operation of a car engine (Mazda Capella GE)

Is everything OK with your car's engine? Is it time to save up for a computer diagnostic or even a repair? A few tips from an automotive engineer with many years of experience repairing imported cars will help you answer these questions.

Before consulting a doctor, each of us performs self-diagnosis. We do not perform X-rays on ourselves, nor do we use an electrocardiograph or other sophisticated devices. We simply feel the forehead, examine the throat, listen to see if there is a tingling sensation in the chest, if the stomach is bloated, if there is a pain in the lower back. Traditionally, we use thermometers and perhaps wristwatches to measure pulse.

This is how, in simple terms, we determine whether the body is functioning normally. And it works!

A car engine is the same organism. There are many sophisticated devices, tools and instruments for its accurate diagnosis and treatment. Various precise methods and techniques are used, requiring a subtle knowledge of the internal structure. We plan to talk about them in detail in the near future.

To begin with, we suggest mastering things that are easier to understand.

Let's try to figure out what you should pay attention to when operating a car: what you need to touch, where you need to look, where you need to listen, and maybe even smell, to understand how the engine feels. If you don't want to study with us, take a hundred dollars out of your wallet and go for a computer diagnostic. Automobile "medical care" is paid!

Initial examination

Imagine that you are a good doctor. Upon entering the room (garage), approach the patient (car), be sure to say hello, say a few kind, reassuring words to him, and offer to undress to the waist (open the hood).

Start with an external inspection of the engine. Remember that nothing reflects inner well-being like a pleasant, well-groomed, healthy appearance.

On the contrary, severe general contamination of the engine, as well as the presence of intense local leaks, indicate poor health. If you prudently placed a clean sheet of newspaper under the engine when leaving your car in the evening, take it out and inspect it. Oil and other fluid leaks that occur overnight will leave marks on the newspaper, which will allow you to identify the source of the leak and determine its severity. The higher it is, the sooner you need to take action to correct the problem.

The next step is to check and bring the level of all operating fluids up to the norm. First of all, we are interested in engine oil and coolant (antifreeze), since their deficiency has the greatest impact on the technical characteristics of the engine.

I would also like to remind you – believe me, I'm not joking – that you need to make sure there is fuel in the tank. Experience shows that some inattentive drivers nearly torture the starter and battery to death, forgetting that first the young man needs to be fed and watered, and only then – on the shovel and in the oven.

At the same time, check the tension of the drive belts of the engine's auxiliary units (cooling system pump, generator, power steering pump, air conditioning). Make sure the straps are not sagging or torn. If everything is okay, dust off your trousers and get behind the wheel.

Before starting the engine

Don't rush to start the engine right away. There's no need to rush! First, turn the key to the "ignition" position... Typically, a series of lights on the dashboard of all modern cars will illuminate. At this stage, we are particularly interested in two.

The first is the oil pressure warning light, the second is the battery charging indicator light, which indicates that the generator is ready to start working after the engine starts. Both of them should glow bright red when the ignition is on, even before the engine starts. But what if one of them isn't lit? If the charging light doesn't come on, that's not a big deal, but if the oil pressure warning light doesn't come on, that's a warning sign. Be careful, you've lost control of the lubrication system! Engine oil pressure is the primary indicator of engine health. Without monitoring oil pressure, you risk having to undergo a major engine overhaul with all the ensuing consequences.

The cause of the malfunction is either poor contact between the terminal and the sensor, or in the sensor itself. As a rule, you should look for the sensor in the area of the oil filter. The malfunction needs to be fixed. Only after you have made sure that everything is in order, start the engine.

cold start

A properly functioning engine with properly adjusted fuel and ignition systems and a healthy battery will start on one try within 3-5 seconds. Consistently occurring cold starting problems indicate a problem. Let's assume we avoided this and the engine started...



Let's look at the instrument panel. The two lights mentioned above should go out.

Caution! If the oil pressure light remains on for 5 seconds, stop the engine!

After a few minutes, try starting the engine again. If there is no oil pressure, you need to look for the cause of the problem.

Possible causes: low oil level, faulty oil pressure sensor; the oil pump oil receiver screen is clogged; the oil pump is faulty; severe wear of the main and connecting rod bearings of the crankshaft.

If the oil pressure is normal, we proceed to inspect the engine in warm-up mode.

Warming up the engine

The speed of a cold engine is approximately 1.5 times higher than the rated idle speed, which is usually 700-900 rpm, and should gradually decrease as the engine temperature rises.

After 7-10 minutes from the start, the engine temperature should reach a level of about 80°C and stabilize (as well as idle speed).

If your car is equipped with a tachometer and a coolant temperature gauge, this process is easy to monitor.

When warming up occurs according to the above scenario, the idle system and engine cooling system operate normally.

If the engine temperature isn't reaching the desired level, the thermostat valve is most likely to blame. There are many more causes of engine overheating, and they are covered in the technical manual.

After the engine has warmed up sufficiently and the idle speed has stabilized (you will find out about this from the readings of the control instruments), it's time to listen to the engine sing.

A beautiful, sonorous voice means a healthy body

Doctors assure that this statement is completely true in relation to humans. The same can be said about the engine.

A properly functioning engine makes a steady hum and "ticks" like a clock. Some mechanics say it "whispers." While these expressions are figurative, you probably understand what they mean.

If the engine runs unevenly, with malfunctions, or periodically vibrates, you should know: this indicates that it is faulty. Sometimes problems are the result of wear on engine parts and a drop in compression in the cylinders, but most often the causes are leaks in the intake tract, a clogged air filter, and malfunctions in the ignition and fuel systems. I would like to focus on those cases when the engine, as they say, "misfires," that is, one of the cylinders does not work.

By disconnecting the spark plug wires one by one, it's easy to find the "saboteur." Once you've located the faulty cylinder, the engine's performance will remain unchanged.

Often the cause of the malfunction can be determined by inspecting the spark plug. This allows you to learn a lot of interesting things about the condition of the engine.

It is impossible not to mention extraneous noises and knocks. Let's make it clear right away that this diagnostic method is a highly technical endeavor and not all professionals can handle it.

Car owners should keep in mind that any sharp metallic sounds indicate a malfunction. If they are "emitted" by mounted units (generator, pump, power steering) - that's half the trouble. You can determine the "culprit" of the noise by sequentially removing the drive belts of these units. If the extraneous noise disappears after removing the next belt, shake the corresponding pulley to determine the radial and axial play of the bearings. More often than not, they are the ones who trouble the peace.



Knocks coming from the inside of the engine itself can be much more troublesome. They are listened to at various engine operating modes using a car stethoscope or, if there is none, a dry stick with a diameter of about 10 mm made of hard wood (it is pressed against the cheekbone below the earlobe). In this way, it is possible to identify defects in the gas distribution mechanism, cylinder-piston group, and crank mechanism.

Let us emphasize once again that in order to make a diagnosis, musical ear is not enough; you need to have professional experience and excellent knowledge of the "matter of fact".

A healthy mind resides in a healthy body

A diagnostic examination would be incomplete without an analysis of the vehicle's exhaust smoke. It's already warmed up enough, so it's time to go to its "fillet" and look under the horse's tail.

The exhaust from a healthy engine is virtually colorless. A barely noticeable light white smoke comes out of the exhaust pipe, the intensity of which increases when you press the gas pedal sharply.

In frosty weather, a properly functioning car leaves behind quite thick clouds of white steam (not to be confused with smoke!), indicating complete combustion of the fuel.

Inhaling exhaust fumes for a long time is more expensive. We turn off the engine. But this is not the end yet. It is worth inspecting the inner surface of the oil filler cap. The presence of traces of dirty yellow foamed emulsion on it is a very alarming symptom, indicating that antifreeze is seeping into the oil. After removing the cap of the expansion tank or radiator, inspect the antifreeze. Caution: To avoid injury, do this on a cool engine! An oily film on the surface of the coolant, as well as foamed motor oil, are harbingers of urgent engine repair.



Well, that's about it. We've thoroughly examined the "patient," literally from nose to tail. And during the inspection, we didn't use expensive equipment that was inaccessible to most car enthusiasts, but rather what nature gave us: sight, hearing, smell, and, of course, the mysterious "gray matter.".

Exhaust smoke analysis

An oily ring-shaped band 6–8 mm wide on the outer surface of a car's exhaust pipe ("mourning ring") is a consequence of increased oil consumption. A major engine overhaul is inevitable.

Black smoke

A sign of incomplete combustion of fuel. The fuel system prepares a very rich mixture and requires adjustment.

Blue smoke (purple) shade

Sign of increased oil consumption. The engine requires replacement of oil seals or repair of the cylinder-piston group.

Thick white smoke

Sign of a burnt out cylinder head gasket. The coolant enters the combustion chamber.

Smoke with the smell of exhaust gases from the removed crankcase ventilation (breather) pipe of the engine

A sign of exhaust gas breakthrough into the oil sump due to increased clearances in the cylinder-piston group.