When buying a used car, it is best to drive it to a service station and have it diagnosed there with the help of a specialist. In the event that this is not possible, the inspection will have to be carried out on our own. If everything is very clear with the body and interior of the car, then how to check the engine when buying?
It is necessary
- - gloves
- - clean cloth
- - white sheet of paper
Visual inspection. Raise the hood of the vehicle and inspect the engine compartment. Here you should pay attention to oil stains and drips: they should not be on a working engine. Even small traces of oil can mean leakage problems for you in the future. Pay particular attention to the areas around the ignition distributor and the fuel pump. Leaks can be caused by both leaky gaskets and rubber seals, as well as loose hose clamps. Another cause of oil traces can be a loose cylinder head cover: inspect the joint, make sure that there are no traces of oil or traces of sealant on it. Even if the current owner tidied up the engine before the sale, he could be missing something. For example, traces of a malfunction of the engine could remain on the inside of the hood, so take a close look at the bolts and nuts: if you find scratches around or on them, albeit small ones, then this may be a clear sign that the engine is at least opened. And it's good if in this case the seller informed you in advance that the engine has recently passed a planned bulkhead.
Inspect the condition of the oil and antifreeze. Check the oil with a dipstick, antifreeze - simply by unscrewing the cap of the corresponding tank or radiator. The oil should be clear, have a normal, not too viscous consistency and odor. The oil should be free of foreign matter or air bubbles, and there should be no streaks or foreign deposits on the dipstick. The same applies to antifreeze: the liquid should be clear, have a characteristic sweet smell, and no oil stains or bubbles on the surface. Bubbles in the liquid are the first sign of a leak, remember: this is a very serious problem. In the case, for example, with antifreeze, bubbles can mean a coolant leak into the engine due to a leaky gasket or a crack in the block head itself, which is completely unacceptable. Antifreeze eats away at the piston rings and causes irreparable damage to the condition of the engine.
Unscrew the oil filler cap. Inspect the lid: under no circumstances should there be foam or plaque under it or along the edge of the neck itself. Dense deposits of the characteristic yellow-white color means that coolant is entering the engine. We already talked about the consequences of such a malfunction in the previous step.
Examine rubber products and candles. The seals and hoses must be free of external signs of damage or cracks.
If the engine compartment is dusty and dirty, don’t be too lazy to put on gloves and arm yourself with a rag to inspect all units: many years of soot can hide many defects.
If possible, unscrew one or two candles: their appearance can tell a lot.
Normally, a very thin layer of light gray or light yellow plaque will cover the candles, and the electrode may be slightly worn out. Candles with a crack on the surface of the insulator mean that the engine will run with a knock, and candles with abundant light deposits indicate the wrong oil. A melted candle center electrode can signal a whole bunch of problems: from early ignition and poor fuel to malfunctioning valves and ignition distributor. Formation of a peculiar glaze consisting of soot or severe wear on the electrodes means that fuel or oil with a large amount of additives was used. Oily spark plugs can be a sign of either too much oil in the lubrication system or more serious wear on piston rings, cylinders, and valve guides. Finally, carbon deposits on the candles indicate improper mixture formation or an air filter that has not been changed for a long time.
Start the engine and gas it on the spot. When starting the engine, the starter should not emit extraneous sounds and rattling. Needless to say, the engine should start on the first try, regardless of the degree of warming up and weather conditions. The motor should run smoothly, without interruptions. If the engine jerks, there are extraneous vibrations, and the rhythm of work can be called inconsistent, then most likely the motor is troit. This means that one of the cylinders is not working. The reason may be a malfunction of the ignition system, incorrect operation of one of the spark plugs, a burned-out piston or an over-enriched mixture. In any case, the problem is worth discussing with the owner.
Check out the readings of the devices. With the engine running, after warming up, the arrows of the oil pressure and temperature sensors should be within normal limits, ideally in the middle position.
Look at the smoke from the tailpipe. If, when starting the engine, the white smoke seemed to you abundant, but then after a short period of time completely disappeared, then most likely it was just condensation, and you should not worry. If smoke continues to pour out of the exhaust pipe, then express diagnostics can be carried out by its color and smell. So, white smoke or smoke with a slight bluish tint, which at the same time quickly dissipates and leaves a sweetish smell in the air - a clear sign of the presence of antifreeze in the cylinders of a car engine. Blue or gray smoke (maybe with a shade of white), which for some time hangs in the air with a light lilac or gray haze, means that oil gets into the combustion chamber. It can be costly to fix both of these problems, so don't risk it. Finally, black smoke means that the air / fuel burns inefficiently. The cause can be many malfunctions: coked air jets, leaking injectors, a faulty lambda probe or an air flow sensor. The consequences are that engine wear is greatly accelerated and the exhaust becomes highly toxic.
Take a test drive. It should identify those flaws that you might not have noticed when the engine is idling. Check how the motor reacts to driving at high and low speeds, how it accelerates and behaves in dynamics under load. You should be alerted by extraneous noises, knocking, uneven operation, a sharp loss of power and, of course, smoke from the exhaust system.