How to Check the Engine of a Used Car

2024 Author: Samantha Chapman | [email protected]. Last modified: 2023-12-17 09:13

No one has ever sold a car because it worked too well or because it was too cheap to maintain, and you have to keep this in the corner of your mind every time you look at a used car, no matter how much you may have fallen in love with it from a distance. However, "used" does not mean "bad" - in fact, even very old cars can still be perfectly reliable if they have been treated well. But before you put your hand to your wallet, it's best to use your head and make sure you're not making a purchase that you will immediately regret. First of all, you need to look at the engine.

Steps

Part 1 of 3: Getting started

Step 1. Check for spots, drips and puddles under the car

Before you even peek in the window, kneel and check the ground under the car for spots, drips or puddles. If there are, try to figure out how long they have been there - are they old oil streaks or fresh stains? Maybe there is also a puddle that is filling up?

• Take a look and determine if this car was just parked on top of an old leak or if it is leaking precious fluids right in front of your eyes. While not always a determining factor, any type of drip, leak, spill or spill can be indicative of much more serious problems.

  

• Dealers and owners will tell you that a small oil leak is normal and this is partly true - some makes and models are infamous for having oil leaks, but that doesn't mean the car has problems. It is up to you to decide whether it is worth adding oil from time to time.

  

Step 2. Identify the type of fluid the puddles are made of

They can also be created by brake lines, cooling systems, transmissions, power steering, or even washer fluid. If you find a wet spot, you might want to swipe your finger over it.

• A reddish fluid is likely transmission fluid. A black one is probably old oil. Caramel is the color of fresh oil from old power steering fluid or brake fluid. If it's green or orange, it's probably coolant.
• Clear puddles could be plain water, in which case it means that it has rained, the engine has been washed, or the air conditioning has been used recently. Once you have some on your fingertips you should be able to tell if it's oil or water based. If it looks like both, be careful and read the following steps carefully.

Step 3. Inspect the frame

Often vendors will wash a car they want to sell, and some will even try to clean the engine compartment, but, as a rule, they will miss the underside of the car. Puddles or not, look how clean things are. You can probably overlook plain old grime, and also expect to see a certain amount of road grime and grease stains (it's a car, after all), but you better be on the lookout for drops of liquid that have formed but haven't fallen yet.

• Check for damp, dark spots, and lumps of dirty oil, paying particular attention to the oil pan and any welds and gaskets you can spot. It is not unusual for there to be some dirt left over from old repairs.
• Either way, dirt or fresh, wet oil can indicate problems, so take note of what you see. Do not hesitate to run your fingers over them (perhaps with a paper handkerchief) to check how dripping, wet, slimy or congealed they can be.

Step 4. Determine if a loss is a problem for you

If you see drips or spills of wet mush, try to figure out where they are coming from. The presence of a leak may be reason enough to move you to the next car in the game, but it will be up to you to decide if it is a sufficient problem to dissuade you from buying the car.

• Some people will gleefully add oil to a leaking tub, and it will go on for years without any serious consequences, other than the expense and hassle it entails. Some spills are minimal, and it can take months before they amount to significant losses, while others get progressively worse and can lead to serious problems.
• If there is nothing that is leaking, dripping or clumping into a pulp noticeably, you can begin to feel calm. A large number of potential engine problems can be ruled out simply by the visible absence of fluid leaks.

Part 2 of 3: Examine the Engine

Step 1. Open the hood and watch for any odors coming from the engine

Before you even start the engine, have the seller open the hood so you can have a look at the engine and watch out for any odors.

• A completely new engine, in perfect condition, should smell like rubber and plastic with a trace of oil or gasoline. At best, you will smell the fumes coming from the straps, pipes and various plastic parts. It's called "degassing", and it's perfectly normal. The smell of an engine compartment shouldn't be much different than that of new tires.
• In a used car, you will almost certainly smell oil. This is normal, and unless it's too intense, it's not something you need to be afraid of. You may also smell gasoline. A hint is perfectly normal, and even a consistent whiff of gasoline-permeated scent is not unusual in older carbureted cars. However, if you hear too much, this could indicate a leak in the fuel system and be a cause for concern.
• You may also smell turpentine, which is basically the smell of old, bad gasoline. This smell could indicate that the car has been standing still for a while. You should ask the seller if there is fresh gas in the tank and how long the car has been standing. This isn't usually a big deal, but stagnant gasoline can cause problems, including rust in the car's tank.
• Another possibility is the sweetish smell of antifreeze. It may simply be from some spill, but you will always need to check for leaks in the cooling system. In a cold engine, they can be recognized by a light green film, a sign that the coolant has evaporated. An acrid, sour smell may also be present, indicating that at some point you need to take a closer look at the battery.

Step 2. Check the engine compartment and its components carefully

Take a look at the engine. Do you see any paint? Of the metal discovered? Sticky substances? Dirt? Remember that it would be best to see dirt or even cobwebs. Dealers and salespeople often clean an engine compartment both out of courtesy and to make it look good. This does not improve the look of the engine, but it can remove traces of leaks and also take your eyes off obvious defects.

• An engine covered in dirt, on the other hand, will show you where every drop of oil or gasoline has been, which parts have been handled or changed (light spots), and will also indicate that the car has been driven, which it means that, at least recently, it has worked. The cobwebs let you know that it has been standing still for a while, which may not mean anything, or that a few more steps are needed later on.
• A caked and dirty engine is both a good thing and a bad thing. It may indicate a leak, but at least you are able to locate the source by following the path of the sewage. If it's just a pile of goo or blackened goo, it might be time to change the seals, or even rebuild them.
• However, this does not mean that the engine has failed or that you will not be able to drive it for years before you have serious problems. A fuel leak will often create a clear stain on an otherwise dirty engine, but fuel leaks are usually hardly noticeable, and you will need to use your nose to notice their existence.

Step 3. Check fluid levels

You will have come across the oil dipstick by now. Take it out, clean it, put it back in, take it out again. Is there any oil? Good. At this point, even if there is oil, its level may also be low. Many cars only show the right oil level if they are hot.

• If it has an automatic transmission, you find another rod in it, so you have to check this one too, using the same take out / clean / put back in / take out method. Again, you want to be sure that transmission fluid is present.

  

• If it has power steering, there will be a pump somewhere. Usually this pump has a lid with a small rod. Check to make sure there is at least some fluid in it. While you're at it, check the brake fluid too. Normally the brake fluid reservoir is semi-transparent, and you can check the level without having to open anything.

  

• Finally, you should also check the coolant level and the washer fluid level. Watch out for all low levels and remember, if you eventually buy this vehicle, fill all these tanks to the right level.

  

Step 4. Examine the belts and tubes

Ask the seller when they were last changed. Cracks in the rubber most likely indicate that these parts will need to be changed soon. With a good cleaning, even old and worn belts and hoses can look fine on the surface, so don't be afraid to explore the engine compartment, pressing on the hoses and pulling on the belts.

• If the straps are a little damaged, remember that they will need to be replaced. Many traders will have already evaluated such issues, but you are not necessarily dealing with a trader, and these things sometimes go unnoticed.
• Most importantly, make sure the straps are present. Many cars don't start without, but some have extra belts that load something or make the air conditioning system work, so make sure every pulley you see has a belt attached or there's a good reason for its absence.
• Check that the cooling tubes are not mushy and soft, a more reliable index of their age than their outward appearance. Check the joints of the pipes and look for the film that reveals hot leaks. These non-waterproof stains sometimes only develop when the engines are hot, so there won't be any dripping, and a good dose of engine cleaner can make them vanish, so look carefully if there's even a trace of residue, more or less. the same size as the limescale you sometimes have to clean out of your kettle.

Step 5. Examine the battery and terminals

Like motors, batteries and their cables can be well cleaned and still be in poor condition. It's not at all unusual for used cars to run out of battery after standing still, so don't be discouraged if at some point the car needs a boost.

• For now, take a look at the battery to make sure it isn't broken or has a leak. Watch out for a bare wire, which isn't all that bad until it's turned green or caked with white residue.

  

• Watch out for the white (or green, or white-green) scale residue on the terminals as well. This is usually just an indication of the aging of a battery that has stood still for a while, and can be cleaned with a toothbrush and carbonated water.

• Again, the best case is a layer of old dusty grime on metal and plastic that would otherwise be clean. This does not mean that the battery is good or that the terminals are not imperceptibly corroded, but it does mean that none of these potential problems have been hidden by the hard work of a dealer.

  

Step 6. Learn about air filters

If you are buying the car from a dealer, the air filter must be new and clean. If you are buying from a private individual, it may be old and dirty, and in need of replacement.

• If the air filter needs to be changed, it is likely that others or all (such as oil, gasoline, air conditioning and transmission) will also need to be replaced.
• If you're not sure or don't want to fumble around the air filter to see for yourself, ask the seller.

Step 7. Make sure the turbo is plugged in and free of rust

If the car has a turbocharger, you probably won't notice it until the car is moving. However, you can at least check for leaks and make sure it is plugged in and not rusted.

Step 8. Take a step back and take a look at the engine compartment as a whole

Each brand and model has a different organization - there could be a rather complex situation or a very simple and trivial one.

• Check for loose cables and hoses. Look for small things that you may not understand but that seem strange to you, such as uncovered holes or potentially missing parts.
• It's harder to navigate newer cars, between electronics (look for burns and obvious damage) and complicated intake systems.
• Older machines are simpler, and are more tolerant of alterations to spare parts. Talk to the seller about any changes or modifications he has made.

Part 3 of 3: Performing the Final Checks

Step 1. Look at the underside of the hood

Stop and take a closer look at the lower part of the hood. Below you will find, if not clear signs, some clues. What you should see is a clean (as usual, normal dirt is not a problem) and intact upholstery, which has the functions of muffling engine noise and acting as a flame retardant.

• A muddy, non-waterproof, and oil-burning car may have blackened the upholstery. If the lower part of the hood is blackened, this is probably not a problem, but if any part of it is scorched, burned or has been removed, it is a sign that there has been an engine fire in the past.

  

• If you find any evidence of a fire, ask when and how it occurred, and you may find that the engine has been rebuilt; if so it is best that you worry about any current oil or fuel leaks.
• A past engine fire should at least make you wary, but even such an unpleasant incident does not in itself mean that the car is in bad condition.

Step 2. Examine the tailpipe

Exhaust pipe leaks are one of the causes of engine fires. You may not see the exhaust manifold well in the engine compartment, but it's easy enough to check the exhaust pipe. The inside of the tailpipe edge should be ash gray.

• If the interior is black, it means that the car has a rich carburetion (too much gas in the air / fuel mixer), which is not a good thing but not terrible either, and usually involves high fuel consumption. The white edges mean that the car has poor carburetion (too much air in the air / fuel mixer), which increases wear damage and causes the engine to overheat.

  

• In older machines this is a valve adjustment problem. In the more recent ones it indicates something wrong with the electronics; usually an oxygen sensor, or perhaps an air flow sensor, which transmits incorrect information to the computer, which then makes mistakes in adjusting the blender. Either way, tailpipe problems will require a tune-up.

  

Step 3. Try starting the car

So: you looked, smelled, felt and grabbed, and so far there is nothing that has scared you, so there is nothing left to do but turn on the car and see if it starts. Three things could happen.

• It starts up and leaves on the first attempt.
• It takes a minute to get it started.
• It does not set in motion.

Step 4. Find out why the car won't start

Did you turn the key and nothing happened? Did the dashboard lights just come on? Check the battery and connections. Pay special attention to the terminals, and make sure the wires are connected well and tightly, and are not corroded. Again, a little baking soda will clean them up enough to maintain good contact.

• The dashboard lights come on, you turn the key and then you hear a click, followed by nothing? This is probably a dead battery or simply a bad connection. Check it and charge it. If needed, remove it, or use jump leads. The best thing is to take out the battery, connect it to an AC charger and wait for some time.

  

• The engine runs, but does not start? Give the accelerator a good push, wait a few seconds and try again. Press the accelerator repeatedly while turning on. If that doesn't work, try again a couple of times. If the car has been standing still, it may just take some time for the gasoline to be pumped from the tank to the engine. With any luck, it will catch at some point and you probably won't have to do it again.

  

Step 5. Take a look at the spark plug leads

If still nothing happens, make sure they are well connected. If you find one that is loose, tighten it and try starting the car again.

• Still nothing? You will probably need to take out the candles and clean them. If the car has a carburetor, you can also try pouring a few teaspoons of gasoline directly into the venturi (the part from which the air enters).
• Sometimes this process has to be repeated entirely, simply to start the engine after a car has been parked for a long time. Finally, if you want to sell a car that has been standing still for a while, start it every now and then, so that this does not happen.

Step 6. After you start it, listen for the engine noise

After starting the car, get out and let it idle as you look into the engine compartment again, and check for smoke or leaks. Feel for gasps, clicks, bangs, or thuds. Sniff for gasoline fumes (there will be some) or a burning smell (there may be some). Here are some things you might hear and what they might mean:

• A "tick-tick-tick-tick-tick" noise, which increases in speed as you rev the engine. It can be produced by stuck tappets, worn cams, loose valves and even a loose belt.
• A "nok-nok-nok-nok" sound that increases in frequency as the engine is revved is called a "knock". That's not good news and could indicate that you should steer clear of this car (unless it's a diesel; in which case that's exactly the noise it should make).
• Squeaking, creaking, screeching? This is usually the belt, or belts, and sometimes the pulleys they run on. Expect to need to change the belt. If the noise continues even after you've changed the belt, you'll need to figure out which pulley it is. Alternators and air conditioning pumps can also make these noises, and they can also make rubbing noises. Watch out for these noises, but unless they start to really bother you, don't worry too much.
• A louder patter that does not match the speed of the revs, but which may be present as you accelerate or when the engine is idling, indicates an engine or transmission mount to change. It is not an emergency, but sooner or later you will want to fix it.

Step 7. Take the car for a test drive

Does everything seem okay? Close the hood and, if you're taking a test drive, take it straight to your parts dealer and have it hooked up to the ECU and check the codes for any other minor problems you may not have noticed. This only applies to cars from the 1980s or newer, and is usually only useful if an engine check light comes on when you start.

• From this point on, you can get help from your parts dealer or mechanic. You've done everything you can to make sure your engine is at least reliable enough to take you to the store. While driving, be on the lookout for any problems, such as a noticeable drop in power, some strange vibration or any other kind of abnormal behavior.
• The code reader can provide you with some details to help you with replacement parts and electronics and adjusting. Your parts dealer has a device that can check your car's computer codes, and most will do it for free, if they have the time. If someone tries to get you paid for a check-up, keep driving to the next one.
• You may need a tune-up or rebuild. If you've made it this far, however, you have a working engine. Congratulations. The fluid pans are full, the battery is full, the tank holds good gas and you are driving. See what it feels like - in the end, that's what matters.