How to check the used car engine
Things you should know before going to check a
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
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
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
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
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.
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
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
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
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
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
- 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.