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How to check the used car engine

Things you should know before going to check a used car

When buying a used car, without a doubt, first check a car history records. Some cars may have been flooded - worthless to buy. Others were written off by insurance due to serious accident. Many cars have altered mileage, and so on.
Follow this link to learn more How to check a used car VIN history report



If looking at the used car you noted any problem with the engine (e.g: major oil leak or strong noise) or any abnormal behavior don't let the salesperson to mislead you. They may tell you, for example, that the leak is "overflow from the recent oil change" or "the noise will disappear later by itself or something like this". Generally, such defects never disappear by itself. If you have hesitation, move on - there are so many cars available.
Whenever it is possible, ask for service records. Look for oil change intervals - was the oil changed regularly? I mean 1,000km (600 miles) over suggested oil change interval won't make a big difference, but if driving, for example, 15,000 - 20,000km (9,000 - 12,000 miles) without changing engine oil, it will cause serious engine problems very soon.
Keep in mind that modern engines, especially those with turbo charger are extremely sensitive to the oil change interval

 
How to check the oil


Locate the engine oil dipstick, pull it out, wipe it and insert it back. Pull it out again and have a close look. If you've never checked the oil level before, follow this link for detailed guide How to check engine oil.
If you find the oil is completely black (note, for the Diesel engine black oil is normal) and the oil level is very low (left picture) - suspect excessive oil consumption and (or) lack of maintenance. In either case the engine will more likely to have problems in the future. Another sign of poor maintenance would be dark stains (carbon deposits) covering the oil dipstick along its length.
Well maintained engine will more likely to have oil level full and oil clean (right picture)

 
Look for leaks

Look for possible oil leaks. If the engine looks very clean and shiny it doesn't mean it has no leaks. Probably it has been shampooed. Most of the dealers shampoo the engine before putting a used car for sale. But there is the trick - look underneath the vehicle using your flashlight. Check the lower part of the engine and transmission. Everything has to be dry. There might be slight wetness which is not that bad, but there should be no leaks. See any leaks? Oil drops on the parking space? - this may indicate a problem.
Note, the water condensations dripping from air conditioner drain tube is normal. This drain tube is usually located on the passenger side of the firewall.

 
If it's possible, look at the internal parts through the oil filler neck (Don't open the oil cap while the engine is running!)


Try to open the oil cap and look inside through the oil filler hole with the engine turned off; Use a small flashlight. If you can see any internal parts there, check their condition. What you looking for is oil sludge - this thick black buildup on internal parts you can see on the picture. For a brighter illustration of how it may look like, I made pictures with engine valve cover removed. It's impossible to open the engine valve cover on each car we check, but luckily, on some models the condition of internal parts is visible from oil filler hole. If you see a lot of oil sludge buildup inside the engine it means that either the engine oil hasn't been changed for a long time, or poor quality oil was used.
Avoid buying such a car - sooner or later it will have serious problems. Mostly such (with thick buildup inside) engines are badly worn regardless of mileage.
For example, compare the two images below: the left Mazda' engine hasn't been maintained too well - it has thick black buildup all over. On the right picture you see well maintained Toyota Camry V6 engine - regardless of high mileage it's still in a good shape. You can see the difference.


 
Check the oil pressure

Try to check the engine oil pressure on a cold engine (after few hours since the engine has been turned off). Start the engine, and look at the low oil pressure warning lamp or oil pressure gauge in the instrument panel. The time between the engine start and you note oil pressure at the instrument panel should be no more than 1 - 2 seconds.
If this time is longer than 2 seconds, avoid buying a used car like this.
If the low oil pressure warning light goes on while engine is running or idle, or the engine oil pressure gauge indicates too low oil pressure, it also means that the engine is worn out or has some defect - avoid such a car.

 
If you find evidence of badly made repairs, avoid any such car.



If you find evidence that the engine has been repaired with inaccuracy (too much bulging of gasket maker, as in the image, loose bolts, stripped treads, altered wiring, broken fastenings, missing bolts or covers, etc.), avoid buying such a car because quality repair is possible only by very skilled mechanics. Just imagine how the engine has been repaired on the inside if it looks this way on the outside?

 
Check the antifreeze level in the overflow tank (never open the radiator or overflow tank cap when the engine is hot!)


Check the antifreeze (coolant) level in the overflow tank. It should be between the "min" and "max" marks, as in this picture. The antifreeze should not have even a spot of engine oil. It should be clean and transparent, it also may be of green, red, blue, orange, or yellow color (depending on the maker).
If you find presence of the engine oil in antifreeze, it may be an indication of a possible engine or radiator problem (a blown head gasket, leaking transmission fluid cooler, etc.).
Look under the car. Check the radiator and water hoses for damage, cracks or leaks. Look at the radiator, it should not have any damage.

 
Timing belt

Many cars, especially with four-cylinder enigne, have a timing belt that needs to be replaced at a certain interval - usually between 60,000 and 100,000 miles (100,000 and 160,000 km). For example, 1993 - 1997 Toyota Corolla, 1992 - 2002 Toyota Camry, 1998 - 2001 Honda Accord, 1997 - 2001 Honda CR-V, 2001 - 2004 Volkswagen Passat - they all have a timing belt. If it wasn't replaced by the previous owner, you will have to do that. It's difficult to check it on the car because the timing belt is protected by the protective covers. The only way is to ask the previous owner if they have a receipt. Sometimes though, dealers place the timing belt replacement sticker somewhere on the top of the engine (see the picture) that indicates the date and the mileage when the belt was replaced.

 
Check the smoke

Start the engine. Let it idle for a 5-10 minutes. Then ask someone to press more than a half way down on the accelerator (to 4500-5000 engine rpm) for 2-3 sec. while you look at the smoke from the exhaust.
If there is cloud of blue or grey smoke, the engine consumes oil. Avoid such a car.
Black smoke means the engine consumes too much gas - possible problem with fuel injection.
Normally, there should be no smoke at all (Diesel engine may have slight black smoke at a cold start - it's normal). A white water steam and water condensate dripping from the exhaust is normal.

 
How to check the air conditioner

When you switch the air conditioner on, the air, blowing out from ventilation outlets should become very cold (not just cool) in a few seconds. There should be no strong noises while the air conditioner is on. If the air is not cold - the air conditioner doesn't work.
Avoid buying a used car after frontal collision. Due to its location (at the very front end of the car) the A/C condenser (part of air conditioning system) may be easily damaged during frontal collision which require to unseal the A/C system. Once the air conditioning system is exposed to the outside air it starts corroding inside which may cause problems with A/C later.

 
Listen for noises when the engine is running

There shouldn't be strong noises, coming from the engine under any condition with no matter is the engine cold or hot. By the way, knocking or tapping at a cold start is one of the indicator of poor maintenance. Knocking, tapping or rattling noises indicate excessive wear of internal engine parts. Whistling may be caused by loose belt. If the engine makes too much noises, avoid buying such a used car. However, Diesel engines are always more noisy, it's normal.

 
Look at the instrument panel

All the warning lights for low oil pressure, low oil level, overheating, "check engine" or "service engine soon" etc, should go off after the engine is started.
I receive lot of questions about "check engine" or "service engine soon" light. You may find the explanation what "check engine" means in the article Why my "check engine" light is on

 
Test drive

Try to test drive a car as long as you can. Try to accelerate, decelerate, go highway if it's possible. The more you drive, the more chances you discover possible problems. If it's your first car, try to test drive few different cars of the same model to have better idea. If you feel anything that may indicate possible engine problem (e.g.: vibration, delays during acceleration, rattling noise, smoke, rough idling, etc.) avoid buying such a car. If you have any hesitation about the way the car drives, go further and shop around more. Usually the sales people are trying to convince you to buy a car today and now because "tomorrow I won't give you this price" or "I have the customer who will buy this car tomorrow" - Don't take the bait - the more you shop around, the more chances to find the right car.

 
Mechanical inspection

As a last step prior buying a used car, have the vehicle inspected by an experienced mechanic of your choice.

 
Do's and Don'ts

- Don't buy a car if you see a smoke from exhaust pipe - only the water steam and water condensate dripping from the tail pipe is OK.
- Don't buy a car if engine knocks or works too noisy.
- Don't buy cars with very high mileage. To be more precise I'd recommend to scratch out anything with more than 230,000 - 240,000km (145,000 - 150,000 miles)
- Don't buy cars that have some engine problems even if it seems to be easy to repair
- Do hire someone knowledgeable to have a vehicle inspected before you buy it.

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