If you are interested in buying your first used car, you will need your wits about you to make sure you don’t end up with a lemon. Sellers try their best to hide the defects of their cars in order to get rid of it as soon as possible.

The car's exterior gives you a fairly clear picture as far as the physical condition of the vehicle is concerned, although there could be more than what meets the eye. On the other hand, an engine is a complex machine and requires detailed inspection but for the sake of keeping it simple, we will talk about five important and relatively basic aspects of an engine:

Smoke

Smoke coming from a diesel car is expected but if you are buying a used petrol car, you will need to find out what kind of smoke is it. Blue smoke from the exhaust means the car is burning its motor oil.

Light blue smoke at the cold start which vanishes after the warm-up is normal since older engines sometimes have worn-out seals and oil drips in the cylinder overnight. However, excessive blue smoke, even after the warm-up, is not a good sign. Steer clear of such cars.

If the smoke is black, it means the car is burning excessive fuel, and it is running rich. Rich prolonged burning means the car engine has carbon deposits in it.

Oil quality and level

Check the oil quality and level of the engine oil with a dipstick. If it looks like a mud-slush, it means the current owner didn’t bother to change the oil for a long period of time. When you lift the car’s bonnet, check for oil residue and seepage around the engine. A small patch of muddy and dusty oil is okay in an old car. It shouldn’t look fresh and/or all around the engine head, etc. That means leaking oil is a persistent problem in that car. Fixing it will require both time and money.

You might even find out the car had something worse done to it, hence the constant fresh oil spots. Open the oil cap and look inside. If you don’t find any black carbon gunk inside, and everything looks clean and shiny, that is a good sign.

Also, ask the owner where the car is usually parked. Looks for oil drip stains on the floor of the owner's garage, etc.

Coolant

Check for the coolant in the car. Open the radiator of the car, and see if the current owner has bothered to use anti-freeze or anti-boil in the car.

Unfortunately, most owners don’t bother to insert an anti-freeze in their cars. Watch out for signs of rust under the radiator cap. If it’s excessive, it means the car has been running on good ol’ plain water for a long period of time. You will find the rust deposits and residue in the reservoir bottle of the car as well.

When you open the radiator cap, check if there is any oil mixed with the water. If you see a foamy substance or oil residue inside, stay away from the car.

Noises in the engine

Do a cold start and keep a sharp ear out for noises. A warmed-up engine would hide a lot of its weaknesses that are only visible when the car is cold. A minor clicking sound from an engine is normal. It is usually the sound of cold tappets. You need not worry about that. The sound will vanish when the car heats up.

Make sure there is no heavy thudding or clunking sounds in the engine, or constant metal grinding. If you find out that the engine is making an unnecessary mechanical noise, you should avoid purchasing or enlist the opinion of an expert. Rebuilding an engine is expensive. You don’t want to end up with a car that lands in a workshop in its first week of purchase.

Test drive

Ask for a test drive. A test drive can help you make up your mind better. Even though, engine is a major part of the car, it is still just one part of it.

Your transmission is another important part of the car. A test drive will allow you to check that as well.

Maybe if you drive the car, you will discover that you don't enjoy the ride even though it looks good otherwise. Not only will a test drive allow you to experience the condition of the engine under load but will also give you an overall picture of the car.

This article originally appeared on Pakwheels.com and has been reproduced with permission.