Many motorists are attracted to cars with a diesel engine because of their unpretentiousness, reliability and efficiency. However, when choosing a diesel, there are a number of nuances that must be taken into account, otherwise you risk spending a substantial amount of money to bring the engine to an acceptable condition.
In this article, we will tell you what exactly you should pay attention to and how to check a diesel engine when buying a car.
First, evaluate the condition of the engine in the same way as when buying any other car: the general appearance of the engine, the presence of oil leaks, soot or corrosion. Also pay attention if the engine is too clean. It is unlikely that an SUV released in early 2000 will have a power unit shining, perhaps this is how they are trying to hide a leak from you.
We also recommend that you (as well as when buying any other equipment, especially by hand) take with you someone who is better versed in this topic and knows how to check a diesel engine when buying a car. If you are satisfied with the visual inspection, proceed to the next step: starting the engine.
It is advisable to check how the engine starts in the cold season (well, or at least in the morning). The diesel engine must start from a half turn if it is necessary to turn the starter longer - the rings or piston are probably worn out.
Also try to start a warm engine - often there is such a situation when a cold engine starts immediately, and a "hot" one - only from the second or third time. This may indicate worn piston rings or a non-working temperature sensor.
Next, you need to check the smoke coming out of the exhaust pipe when the gas pedal is pressed. If it is black, it is most likely that the oil scraper rings have worn out and oil is getting into the fuel. It is also possible that the nozzles are worn out, which is much worse.
If smoke is present, but it is white, water gets into the fuel (usually this can also be recognized by the uneven operation of the engine at low speeds, it works "jerks").
Next, open the oil cap and see if oil comes out from under the oil filler neck (sometimes it can even splash). There can be many reasons, in principle, it is quite amenable to elimination, but the presence of such a defect will allow you to seriously bring down the price if everything else suits you.
You should also evaluate the sound of the engine itself. The sound should be soft, but powerful, bass, without the presence of various kinds of noise. Try to hear sounds that are not included in the overall rhythm, and also "drive" the engine at different speeds.
If this car suits you, and you still decide to take it, then the first thing you need to do is start measuring compression (although it is advisable to do this even when buying). For a diesel engine, the optimal compression value is 25 atmospheres, although much depends on the specific engine model, but, as a rule, compression of a lower indicator indicates malfunctions.
Moreover, the smaller the compression difference between the cylinders, the better (the optimal value is 0.5). Of course, one cannot expect such a thing from a used car, but if the spread is really strong, it means that soon the engine will need to be overhauled.
Also, compression can be approximately estimated without special equipment (although it is still advisable to use a compression gauge). Unscrew the oil filler cap, but do not remove it, and ask your friend to keep the gas pedal depressed. If the engine retracts the cover, then there are no global problems, if it pushes it out, then the compression value is much less than necessary.
In addition, you should not warn the owner of the car that you will check the compression, as there are additives that increase it. You will be misled, and these additives are not very useful for the engine.
In addition, immediately after the purchase, you should buy a new timing belt (even though the previous owner claimed that he installed it a week ago). Moreover, it is advisable to take a branded one, even if the price bites - if a poor-quality or worn-out belt breaks, it can turn the entire cylinder head, and this is completely different money (not to mention the fact that the belt can break at the most inopportune moment).
We hope that our article helped you understand how to check a diesel engine when buying a car, and you can choose the right car that will serve you for many years!
When choosing a car with a diesel engine, a person wants to get reliable and economical transport, let's figure out which diesel engine is better and how to choose it so as not to be mistaken.
Before buying, you should always carefully examine the engine for oil streaks and traces of antifreeze. If traces of antifreeze are found on the engine, then most likely the owner of the car has overheated it too much, and if traces of oil are visible, this may indicate a large age of the engine and worn parts.
Remove the air pipe and see if there is oil in it, if it is, then this indicates the wear of the cylinder-piston group. However, oil in the pipe may appear due to a clogged air filter, so this should also be checked.
Starting the diesel engine will help determine the health of the diesel engine, it should start instantly, except in cold weather. When starting, a small smoke should come out, and immediately disappear, this is normal for a diesel engine.
The next step in checking a diesel engine is its cooling system. Wait until the engine is completely cool and check the coolant level in the radiator and expansion tank. The radiator should be full to the top, and the amount of liquid in the expansion barrel should be at the level of 50%. After checking the cooling system, restart a cold engine to make sure it starts instantly. It is best to buy a car with a diesel engine in winter, as its performance will be immediately visible by the way it starts in cold weather.
Now you need to check the diesel engine on the track. Based on the size of the engine, you must determine how quickly it picks up speed. If the car, in your opinion, accelerates too slowly, then this may indicate a worn motor and poor compression.
Get out of the car and ask the car dealer to press the gas pedal while you look at the exhaust. The smoke should be almost invisible (depending on weather conditions), if you see a pronounced blue, black or white smoke, then this indicates an engine malfunction.
Also, when choosing a diesel engine, pay attention to the sound of its operation, there should not be any extraneous noise. If a whistle is heard at increased engine speeds, then most likely the engine intake system is not airtight. If you hear an extraneous howl or creak during acceleration, then it may be a bearing.
For a general development, take a look at the video, which shows the principle of operation of a diesel engine.
So, you have decided to buy a car with a diesel engine. For a post-Soviet person who did not work in the past as an Ikarus or KAMAZ driver, the word "diesel" always aroused a kind of sacred awe - this creation of the human mind seemed to be a very complex, dark and incomprehensible subject. Therefore, a daredevil who decides to take such a desperate step - to drastically change his usual gasoline life and buy a car, not only is it imported and not new in the vast majority of cases, there are many questions about what to do with this car before and after purchase.
Do you want to buy a diesel car
What should you pay attention to when buying? To begin with - for everything the same as when buying any car (general condition, mileage, corrosion centers, and so on). If you are buying from a stranger - don't let them know in advance of your plans to test something - catch them by surprise with the following test:
- How to start a cold engine (in the morning, for example).
If you have to turn the starter at least a little more, this is already an alarming sign (wear of rings, piston). In this case, it is desirable that the engine be completely cold when starting. A serviceable diesel engine should start with half a turn. Cold diesel noise, quite noticeable. Warmed up - much quieter. Try to start a hot engine, on some models the heating does not turn on and the start is due to compression.
My car has a similar pattern. On a cold one, it starts with half a turn, and on a hot one, you have to make from 3 to 10 attempts. After disassembly, the diagnosis was confirmed - the wear of the rings. However, this may not happen on all machines: some have a sensor - if the temperature on a warm engine is insufficient to warm up the combustion chamber, then the glow plugs turn on. Another thing is when this sensor does not work.
- and the condition of the fuel equipment.
When you press the accelerator on a warm engine, check for smoke coming out of the exhaust pipe. If the smoke is dark, then, most likely, the oil scraper rings are worn out, or the injectors are out of order, in general, nothing good. If it's white smoke, water is getting into the fuel somewhere.
A simple method: put a piece of paper under the exhaust and look - if there is soot, then most likely it is eating oil (oil soot) or incomplete combustion of fuel. If there is a turbine, then black smoke can go until it is turned on. On the move, there may be black smoke when re-gassing, but it is short-lived and not thick. Smoke may also be due to a clogged air filter - try running the engine without it.
- The sound of the engine.
If the sound is uneven, tapping, it is possible that the valve clearance is incorrect in the engine, or something is wrong with the valves themselves or the piston. It is possible that everything can be corrected with elementary adjustment. By the sound of the engine, you can also assess the condition of the fuel equipment: - "hard" sound, black smoke at high speeds - early injection angle; - interruptions and gray smoke at idle and black smoke and interruptions at high - late injection angle; - uneven idling and black smoke - a non-working nozzle, you can definitely determine this by turning it off. The pump should not "strum".
The engine should work softly, - "rumble" solidly, in a word, "in a diesel way". Try to hear (although it is difficult on an unfamiliar diesel engine) extraneous noises at different speeds, when they are set and reset, how the piston and crankshaft work.
- Open the oil cap.
If oil squirts from the oil filler neck, this is an indicator that there is a gas breakthrough somewhere (or maybe the guides are just broken). This thing, though unpleasant, but not fatal. There can be many reasons - both serious and curious.
At the same time, you can seriously bring down the price - shaking your head and speaking out in this way: “Yes, you, man, the engine is dead! that this is not so - in life it will not prove until the compression is measured.
- General view of the underhood.
Determine if the nuts of the nozzles, cylinder block, traces of white or red sealant (for the Japanese - only black) are not jammed - it means that they climbed into the engine here. All accessory mounting bolts must be in place. Only in our service they can easily not put a hard-to-reach bolt.
The condition of the liners can be assessed by warming up the car, turning off and immediately turning on the ignition: the oil pressure light should light up after a couple of seconds. If earlier - either the oil is liquid, or the liners are not in order. The second is faster.
More complex procedures:
If you have completed all of the above steps and after that you are not disappointed in life, then this is already good. Even better if you still want to buy the same car. Then, if you have the opportunity, it is strongly recommended to perform the following actions, which speak volumes (at the station or, if possible, better with friends).
A. Measure the compression. Correctly it is measured like this:
- Unscrew all injectors.
- The starter “flashes” the cylinders a couple of times to prevent oil or fuel from entering the cylinders, which can affect the compression value.
- Screw the compression gauge into place of the nozzle and turn the engine several times with the starter until the arrow stops.
- Everything is repeated on other cylinders. Compression should be, firstly, not lower than 25, although it may be different for each volume. The smaller the spread of values by cylinders, the better. The standard for a new car is 0.5, no more. For an old car, this, of course, is not feasible, but if there are values like 18-25-30-22 at a rate of 25, this indicates the possibility of an early overhaul.
If the compression is low, it's not the end of the world. To begin with, you can find out what is the cause - and, accordingly, how much the repair will cost. Low compression happens for two reasons:
- Piston wear (there is a breakthrough of gases through the gaps between the sleeve and the piston)
- Valve wear (gas breakthrough through guides, seals).
To check, take a little oil in a syringe, inject into the nozzle hole, screw in the compression gauge again and measure the compression again. The idea is simple: if the rings are worn, oil flows into the gaps and does not allow the gases to break through, and the compression should increase. If it remains as it was, then the valves are worn out, which is both cheaper and easier to repair. Yes, and do not inform the seller of your intention in advance - otherwise they will pour in some filth to increase compression, then you will not end up with problems.
B. Check the injectors. A normal nozzle, when fuel is fed into it under pressure, should emit a very characteristic "beech-beech-beech" and spray "into the fog": All sorts of rain and trickles are not welcome. Increased black smoke can still occur if the cut-off in the injectors does not work. Sprayers need to be removed and inspected. Spraying in the form of drops and streams is categorically not recommended - you can burn the pistons or the head, depending on where it sprays. Determine the condition of the fuel supply and return hoses. If the tightness is broken, then there will be problems with starting.
B. Glow Plugs/Heated Combustion Chamber. The inclusion of the heating relay is checked by ear and by the lights on the dashboard. By the speed of switching off the relay, it is possible to determine idle candles. Using a voltmeter, you can first trace that 12V is supplied to the candles. After starting or after 5-10 seconds, it drops to 6V, and after the engine warms up - to 0. But on different machines in different ways. If the candles, designed for 8 sec. put on a car with a relay that gives out 13 seconds, there is a high probability that they will burn out. And the speed of turning off the relay does not mean anything at all - it gave out 10 seconds. and turned off, and the candles may be faulty. What’s more, we can’t tell anything by ear.
D. Oil color. The color of the oil is black, without foreign inclusions. A quick, somewhere in 500 kilometers, darkening of the oil after changing it (not due to a mixture with the old one) is an indirect sign of wear on the rings. If the oil has a characteristic silvery-gray tint, then there is a fairly high probability that the engine has been "treated" with some kind of molybdenum additive.D. Cooling system. There should be no bubbling in the cooling system, this is checked at medium and high speeds on a warm engine. If there are bubbles, the gasket has burned out, or the cylinder head has moved. Estimate the thermostat response time, the engine at idle may not warm up above 40-60 degrees, but after 5 minutes of driving, the arrow on the scale showing the temperature of the coolant should show the operating temperature. On the iron pipes of the cooling system near the block there should be no rust and a characteristic red coating, like the exhaust manifold - a suspicion that it was overheated.
E. Measure crankcase gas pressure. High pressure indicates, again, the wear of the piston or valves.
Immediately after purchase
If you are not afraid of all of the above, and still bought a car, then immediately perform the following magical steps:
- Change the timing belt immediately after, no matter what the seller tells you there. Take a branded belt, do not buy cheap. If, God forbid, it breaks, the valves cover at least. Have the belt changed by a specialist. I saw an Audi with a head of the block torn off and thrown into the trash only because the owner was stingy to buy a good belt.
- After purchase, watch the oil level. If the level drops without visible oil leaks, this is a clear sign of worn oil scraper rings.
Change the oil and fuel filters, regardless of when the dealer says he changed them. Especially if you bought a car on the eve of winter. - Naturally, when performing the above actions, it is desirable to change the oil. I recommend: Shell Helix Ultra Plus 5W-40 synthetic. Started at -33° even with very poor compression. P / synthetic Chevron Diesel SAE 10W40 API CF / SE plus REDEX molybdenum additive. By the way, it is best to take oil with API CF or CE classification. CF is the best. CC and CD are designed for diesel engines operating at medium loads, which is not very suitable for our fuel. Abroad, for old diesel engines, it is just right, but in our country all conditions must be considered the most difficult and unfavorable, and oil should be taken accordingly.
- In addition, study the numbers on the battery that you got with the car. A diesel engine, especially if it does not have very good compression, needs a good battery to start the engine (recoil current: the more the better), thinner oil and a working heating system. I have, for example, 100Ah / 450A at - 18.
- Also, as a primary event after the purchase, we advise you to carry out diagnostics at the service station (costs from 30 to 60 dollars), which can tell a lot about the car. Although the stations are also different and they can say different things. So don't be too scared. It is best to ask the opinion of several experts (they tend to be very contradictory).
Some time has passed since the purchase
So you're driving your newly acquired diesel car, and hopefully getting a lot of buzz out of it. But somewhere in the depths of the soul, the thought torments: “Now it’s good, but some time will pass and ....” What should I do to prevent this “and ....” from happening? It is difficult to advise here for all occasions, but some general advice can be given:
- Don't fill up at random gas stations. If the color of diesel fuel confused you, it is better to look for another gas station. Always have a watering can with a mesh (preferably double) on hand to prevent dirt from entering the tank.
- Avoid "cheap" options from nowhere (tractor, ship, diesel diesel fuel). It's very hard to guess here. We once took a chic diesel diesel fuel, but our friend, or rather, his car, suffered greatly from the ship's diesel fuel. Refuel only if someone already drives this diesel and is satisfied with it.
- Change the fuel filter more often than required by the service book. With the quality of our fuel, this is a decisive factor for the normal operation of the machine, especially in the cold season. You can put an additional fuel filter.
- Do not spare money on oil, especially for winter. For our winters, mineral water 10W30, semi-synthetic 10W40, synthetic 5W40, other SAE markings are best - see the catalog for temperature limits.
- Fuel and oil additives.
We do not recommend getting carried away with the addition of additives, especially cleaning ones, and especially of unknown production. The cleaning additive has the ability to wash out all the dirt and muck from the tank and pipelines and drive it all into the fuel pump, the filter cannot hold everything. The result is high repair costs for the pump and/or motor.
For the winter, you can stock up on anti-gel. I use Kleen-Flo (Canada) and REDEX (GB). Antigel should be added to the fuel according to the instructions and until the diesel fuel thickens. After that it won't work anymore. Although diesel fuel from new, decent gas stations at a more or less low temperature (about -10-15) should not gel much.
I highly recommend the REDEX molybdenum oil additive. Firstly, the molybdenum compounds contained in it enter into molecular interaction with the rubbing surfaces in the engine and create a thin protective layer that reduces wear and friction. Secondly, these compounds tighten microcracks and small surface damage. It lasts for 75,000 kilometers, i.e. the protective layer is not washed off at. In practice, this is expressed in a sharp decrease in engine noise and fuel economy. This is not an advertisement, I tried it myself and am very satisfied.
You can also add a few so-called conditioners, i.e. additives designed to improve fuel performance. Manufacturers attribute to them the magical effect of binding water, increasing the cetane number, reducing consumption, etc. I gradually add again the REDEX conditioner. It doesn't seem to do any harm. Try to buy all fuel additives from the same company. They all seem to be compatible, but it's better not to risk mixing additives from different companies.
Do not experiment with additives to increase compression - when you need to replace rings - "You can't revive a dead man with poultices", and they can do much harm.
Cars with diesel engines have recently begun to gradually replace their gasoline counterparts. There is nothing particularly surprising, since diesel engines are characterized by increased reliability, economical consumption of fuel resources. However, it is wrong to blindly buy a car knowing only that it consumes diesel fuel. The engine or its individual components can exhaust their resources, so pay maximum attention to checking. An old and neglected engine will smoke excessively, "eat" an unexpectedly large amount of diesel fuel, and also prevent the car from starting normally. Therefore, experienced motorists recommend carefully inspecting the vehicle, including its engine. Not everyone knows how to check a diesel engine when buying a used car, so we recommend such motorists to take the advice of experienced drivers.
How to test a diesel engine before buying a car.
We check the diesel engine before buying
Checking a diesel engine is important not only to find out what technical condition it is in. Such an inspection allows you to understand the parameters of the engine, to clarify how they match your expectations. It's no secret that automakers equip vehicles with diesel engines, as well as turbocharged counterparts. Even these two types of engine are accompanied by significant differences. If you are a fan of high-speed driving, you appreciate the maneuverability of your car, then choose a car among vehicles equipped with turbocharged engines. However, in this case, accept the fact that you will not be able to save on fuel. If the priority for you is the economical consumption of diesel fuel, and you are ready to put up with an insufficiently high speed limit, then purchase without turbines. However, in any case, it is extremely useful to inspect the engine so as not to buy a "pig in a poke", and subsequently throw out incredibly large sums of money for engine repairs.
You should not abandon the idea of \u200b\u200bconducting an audit yourself, for fear of a lack of experience in conducting such procedures. After reading the instructions, you can easily figure out how to check the diesel used car. During a visual inspection, we recommend starting the car and carefully listening to how it works. It is important that he does not sneeze, does not rattle, but starts smoothly and easily. We also recommend that you go from the “rear” and observe what exhaust gases are coming out. If solid black smoke comes out of the chimney, then something is wrong with the engine of this vehicle. It is especially recommended to immediately abandon the car if not only black smoke is coming down, but also the suspicious knock of a running engine is clearly audible. Also, do not be too lazy to open the hood and inspect the interior "decoration" for cleanliness. Some diesels, even if there are problems, still start up quickly, but traces of pollution can tell about existing problems.
Checking the condition of oil and antifreeze
Let's continue the visual inspection of the power unit. Do not buy a car until you are convinced of its reliability and technical serviceability. So, check the cleanliness of the motor before buying. If you find traces of oil or antifreeze on it, you should suspect that the owner overheated it excessively. Also, traces of such pollution can tell about excessive wear of engine components. Of course, oil can also be thrown onto the surface of the engine in cases where the air filter is clogged, therefore, in order to get to the bottom of the reason for splashing out antifreeze or oil. Experienced motorists recommend purchasing diesel cars in the winter, as it is much easier to make sure that the engine starts well at low temperatures.
The principle of operation of a diesel engine is different from a gasoline counterpart. In particular, the ignition of the air-fuel mixture occurs from the glow plug during the compression process, in gasoline cars - from the spark plug due to the occurrence of a spark. There are two types of glow plugs installed in diesel cars:
- ceramic;
- pin.
Such glow plugs very quickly heat up to a temperature of 850 to 1000 degrees. The glow plugs will continue to glow until the coolant temperature reaches 75 degrees. You can check the health of the glow plugs using a multimeter by selecting the circuit test mode. To do this, one probe is brought to the body of the candle, and the second to the cap. Now notice if the circuit is closed. If yes, then the candles are in working order, so the engine will start easily. Otherwise, you will have to go to the auto shop and purchase new glow plugs.
Extraneous sounds and engine vibration
As mentioned above, checking a diesel should necessarily consist in listening to the sounds of a running engine. Refuse to buy if you hear a clear clatter and rumble. Think of sounds like "sos" to indicate that the engine is about to stall. If you start a diesel engine and start to hear a quiet tapping, you can not strain, such work is quite acceptable. Further at idle, we recommend increasing the speed (from 3 to 4 thousand revolutions per minute). Even with such an additional high-speed load, the engine should work quietly. Discard the car if you notice an increase in vibration and excessive jerking of the car when increasing the speed.
Exhaust gas color analysis when checking the motor
As all drivers know, it is very bad when black smoke comes out of the exhaust pipe. However, not only the black color of the exhaust gases should be alarming. Increase the engine speed to four thousand at idle and see what color of the exhaust gases will be observed. Blue smoke indicates that there is already some kind of problem in the engine, and blue smoke may indicate a late ignition. After that, we recommend that you press the gas pedal. Of course, more smoke will come out of the exhaust pipe. If it is also gray, and the engine starts to vibrate, then this car will significantly lose power while driving. Think, either you will immediately need to carry out repairs, or simply abandon such a car and look for better options.
Checking the engine while driving
After we checked the performance of the car in the garage, we suggest continuing the check when purchasing a used car while driving. Start the engine and start moving. Step on the gas pedal and see how the car obeys you, whether it picks up speed quickly. If the car is slowly picking up speed, it means that the engine is most likely worn out or it has poor compression. In the process of picking up speed, listen for extraneous sounds. If you hear squeaks, think about the performance of the bearings. Compression is best checked at a service station, as the craftsmen have special instruments. In garage conditions, compression can also be checked, but you cannot absolutely trust the result obtained, since an error is not excluded.
To finally verify the performance of a diesel car, we recommend that you take a ride on it by conducting a kind of test drive. So you can evaluate not only the operation of the engine, based on the sounds made, smoke coming out of the exhaust pipe, but also make sure the level of diesel fuel consumption.
So, by checking a diesel car, you will save yourself from unpleasant surprises. We are sure that you will now be able to carry out all the actions correctly, thanks to this you will get the best car for yourself.
More recently, automakers have amazed the world with the release of diesel versions of sports cars. The Audi TT, the Škoda Octavia RS or the Peugeot 406 Coupe seemed to encroach on the core values of sportiness: a manual transmission, rear-wheel drive and a petrol engine. Probably, it could not have been otherwise - the opportunity to drive in style and economically seemed too tempting.
Diesel "Audi TT"
In the last decade, diesel models have become popular in most vehicle classes, from small city cars to large all-terrain vehicles, as well as the already mentioned sports cars. People choose used diesel models even despite the somewhat higher operating costs - everything is overshadowed by low fuel consumption.
Here are some tips on how to test a diesel car yourself when you buy it. By following the steps already mentioned, you will reduce the possibility of acquiring a bad vehicle:
- Unscrew the oil fill cap, but do not remove it. Ask the owner of the car or the person accompanying you to hold down the accelerator pedal of the car for a while. Check the cover: if the engine pulls it in, everything is fine, if it pushes it out, the engine compression is probably already too low.
- Inspect the lid itself - there should not be any deposits of a pasty consistency on it. If they are still there, this may indicate an overheated engine or an untimely oil change.
- Until the owner of the car or your friend got out of the car, ask him to press the accelerator pedal harder. Keep an eye on the exhaust pipe: if what you see resembles a light black smoke, it's okay, but if thick bluish smoke pours, you may have to change the turbine in the near future.
- Select the so-called oil dipstick and pay attention to whether steam or smoke rises from the hole. They shouldn't be. True, this advice does not apply to new cars.
- Do not rush to turn off the car engine. Let it warm up to operating temperature. Then turn it off, wait 5 minutes and try again. The motor should start running instantly. If this is not the case (i.e., the engine starts to work only after 2-3 rotations of the crankshaft), you will probably have to visit a car service in the near future.
- Avoid the V-shaped 2.5 TDI engine, which was installed in the cars "Volkswagen", "Audi", "Škoda". Due to its defective design, it requires more maintenance and cannot always answer with its durability.
- Keep in mind that even in a new car, the engine can be dirty and, experienced people say, this is nothing to worry about. The main thing is that there are no traces of oil smudges on it, indicating more serious problems. So take a close look at a ten-year-old car that has a clean engine. Washed it, probably not in vain. And it is better to be accused of morbid suspicion than to buy a bad car.
Good luck with your choice!