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Expert buying - How to check a Car’s Engine

Ishaq Nabi
by Ishaq Nabi


5 min read

Expert buying

Checking the engine of a car seems like a very daunting task to a normal person. You might have asked a friend or relative who claims he is an expert at judging cars. However, that is not always possible and sometimes these people can make mistakes as well. It’s always better to have the ability to decide for yourself.

If you think only an expert mechanic can judge a car’s engine well, we are here to tell you that that’s not true. You can accurately judge any car’s engine if you look closely. With the tips that we are going to mention below, you will be able to tell a faulty and well-functioning engine apart.

So without further ado, let's start with these points.

Check engine light

We know, we know. “It’s too obvious”, you say but believe us when we say this that buyers do overlook the check engine light. This could either be due to a lack of knowledge but it could also be a manipulation by the seller. Sometimes, sellers convince buyers that the check engine light is due to some minute problem for which they are ready to lower the price. The buyer later finds out that the problem was way bigger than claimed by the seller but by then it’s too late.

Moreover, you will often come across cars whose check-engine light has been disabled by the seller. This has become a common practice but there are ways to enable this light back. However, the techniques to enable the check engine light varies a lot depending on the car model and make, or the technique used to turn it off in the first place.

Therefore, it would be wiser to follow the rest of the points we’ve mentioned below.

Check the sound produced by the engine

Before you do anything, even opening the bonnet, look for any unnecessary sound produced by the engine. Of course, you’ll have to start the engine for that, but that’s all. Don’t mistake the clicking sound of tappets with faultiness. That’s just normal. However, look for sounds like these:

(Put Bad engine sound)

This is what a good engine sound looks like:

(Put a good engine sound)

Don’t overlook a bad engine sound. It can end you up in big trouble.

Take a compression test

When you’re checking a car for purchase, you have the right to check its plugs. You can do that using a socket. If you hire a mechanic to check a car for you, he will have these tools. Since you need to take out the plugs, you can go a step further and do a compression test. This is something that a lot of people do not know.

A compression test will tell you how much pressure your engine makes. To do this, you will have to take out the spark plug, one at a time, and plug in the compression tester. Start the engine and you’ll have a reading on the tester. Note readings for every spark plug on a piece of paper.

Once all are noted, you'll notice that they are quite the same. Now observe if they are 10% above or below their average. If that is the case, then the engine is good. If not, there could be some problems with the engine that you don't want to deal with.

If the above process seems too Herculean to you, you can acquire Carmandee’s car inspection service that includes this test.

Check the oil of the car

The first and most obvious thing you need to do to check the oil of a car is to pull out the dipstick. The first time you pull out the dipstick might not give you an accurate reading of the oil level. So clean the dipstick with a piece of cloth, put it back in, and again pull it out. This time notice the level of the oil on the dipstick. If it is lower than the marking, it either means that the owner has not changed the oil in a long time or it can also mean that the engine is not in a good condition.

Another thing you should notice in the oil is its quality. If it's concentrated with tiny dust particles then that’s not a good sign. A good engine and timely changed oil will always be clear and viscous.

If you find that the quantity of oil is low, look for any signs of spillage on the parts below the engine. If you’re checking the car out at the owner's house, you might notice some stains on his porch or garage. This is a red flag and we recommend you avoid such cars.

In case you really like this car, ask the owner why the car is leaking oil. If he says that it’s a minor problem, ask him to fix it and then sell the car to you. If he doesn’t agree on this condition, then it’s highly likely that the problem is a big one and he knows it’s going to be a huge dent in his wallet that he doesn’t want.

Check the radiator

While the radiator is not directly related to the life of the engine if it contains oil that means the oil from the engine has leaked into the radiator. This will only happen if the engine gasket has leaked, which would require opening up the whole engine. This is a lengthy process that you don’t want to undertake in your newly purchased car.

Before you go on removing radiator caps, make sure that the car is cooled down. If you open a car’s radiator cap right when the engine is hot, the coolant or water inside would shoot out. This water or coolant might be so hot that it might burn your face or hands. So, make sure you avoid this mistake.

Observe the car’s smoke

In the case of a petrol car, it’s completely normal for a car’s engine to emit white or even blue smoke for the first few minutes.

However, if the blue smoke remains constant that is an indication that either the piston rings, the valve seals, or the gasket is weak. These are very major issues in a car and therefore should be avoided at all costs, except if you like spending time and money at the mechanic.

Black smoke means the car’s engine is not burning excessive fuel. The reason for this could be either the fuel injectors are adding too much fuel or that the intake valves aren't getting enough air in. This can require a full overhaul of the engine, a situation we recommend buyers avoid.

Final Words

We know these tips might be too much for some of our readers but once you get the hang of it, you’ll be able to tell of a bad car engine so easily. This knowledge will come in handy for the rest of your life and you won’t be dependent on anyone to help you find the right car. Moreover, you’ll be able to get your car fixed by a mechanic and not get taken for a ride.

If you liked this article, check out our other articles on Expert Buying, where we’ve broken down every aspect of checking a car. From the car’s paint to it’s suspension and even documents, we have covered all aspects with expertise and also with sincerity to our readers.

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