You don't need me to tell you how important the engine is in a car so checking it thoroughly is one of the main things when buying a used car because how worn the engine is when you buy it depends how long it will last when you own it. If you were to replace the engine in some cars the engine can cost more than the car when buying the engine new. There are a number of checks you can do so to make sure you check the engine properly, follow the steps below:
The internal engine
Just by looking at the engine on the inside you can tell if it has been properly maintained, a poorly maintained engine will more than likely have a thick sludge over parts inside the engine. This sludge will be the result of low oil levels or poor quality oil being used, the oil affects the engine greatly and eventually can cause the engine to fail even though many think of it as a small factor in the maintaining of your engine. A well maintained engine will still have some dirt but it should not be thick and oily it should be fairly clean in comparison to the poor one. If the engine looks suspiciously clean then you should check the oil its self if the oil colour is light brown then this is a good sign, however, if the oil is black then there is definitely a problem. Also if the oil looks clean and was said to have been changed that morning after your test drive check it again just to make sure the oil being flushed through the system is as clean as that in the tank.
If the car has blue smoke coming out of the exhaust then this means the engine is pulling oil through the cylinders and burning oil in the system. This, as you may have guessed, is not a good thing for the condition of the engine and can eventually cause it to fail. It is usually caused by a leak in one of the engine valves and is quite difficult to restore so if the car shows a sign of this then it is advised that you don't buy the vehicle as there will be many more costs on top of the price you pay finally.
Under no circumstances should the engine make loud noises so turn the engine on and listen for any noises coming from the engine. If the engine makes loud rattling noises then this could mean the parts in the engine have had excessive wear. If there are any whistling sounds coming from the engine then this could mean a loose fan belt. If the engine does make lots of noise then it usually means it will soon require quite a lot of work, however, bear in mind that diesel cars will always be slightly noisier than petrol cars so some noise is to be expected from diesels.
If you are unsure on checking any part of the vehicle you can always hire a professional to look at the engine for you. This is advised especially if you think there may be a problem but you can't find what it is, if you can find the problem then you may be able to get the price of the vehicle reduced.