Free Auto Repair Advice by Certified ASE Technicians
Troubleshooting
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Why Does My Engine Make Noise
Engine Noises
Introduction
Today's engines have been designed with more complexity and moving parts than
ever before. Most of the time when you hear a tapping, squeaking, whirring or
rattling sound there is something going wrong. Excess engine noise is due to
excessive clearance between two metal parts that should have little to no
clearance. This clearance can be due to several things from a broken valve
spring to a valve lifter sticking. Identify where the engine noise is being
generated, with the engine running try to isolate where the noise is coming from
in the engine, either the upper half, lower half, front half or rear half.
Listen from above the engine or below the engine as this will help determine
where to start looking for the cause of the noise. To avoid engine
noises
change your engine oil every 3,000 miles. We have listed the most common
reasons for excessive engine noise below. Some engine noises are normal for
example: some
Chevy
and Ford
engines have short skirt pistons or all roller valve train, a minimal amount of
engine ticking noise is normal. Most cars have fuel injectors that will make a slight
clicking noise when the engine is idling. These noises are normal and no repair
is required, but if you have other unexplained noises we have listed the most
common reasons for engine noise.
Car Repair Guide - READ COMPLETELY BEFORE BEGINNING!
- Step 1 - Engine Making a Tapping, Clicking or Rattling
Noise (lower and upper engine noise) -
Check the engine oil level, your engine depends on clean engine oil to lubricate
the internal moving parts, if the engine oil level is low or the oil is dirty
it can cause internal engine parts to malfunction. For example: a valve lifter
is responsible for holding valve train clearance to a minimum, if the oil level
is low or dirty it can cause the lifter to malfunction which will allow excess
valve train clearance creating engine tapping or clicking noise. In extreme
cases or when your engine has run out or close to out it can cause one
of the many bearing surfaces to fail causing permanent engine damage and noise
until repairs have been made. If this condition is left unattended the engine
will suffer permanent damage and fail. If your engine is making a noise
change the engine oil and filter
with the manufacturers recommended weight (viscosity) oil first, if that
does not make a difference engine repair work is needed
Change Motor Oil and Oil Filter
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Step 2 - Engine making a Squeaking, Squealing, Chirping or Rattling
Sound (front engine noise) -
To check for a
squeaking noise that could be generated by the engine accessories, accessory
mounts, drive belts or drive pulleys. When an accessory, accessory bracket,
belt or drive pulley fails it can make a rattling, squeaking or tapping
noise. These sounds are centrally located near the front of the engine. With
the engine off, check the tension of the belt/belts, it should be at medium
tension a loose or worn belt can make a loud squealing or chirping noise,
check the belt tensioner and the size of the belt to make sure the right
belt is installed. To isolate the origin of the noise, remove the main drive
belt and start the engine. If the sounds disappears an accessory, accessory
bracket, belt or pulley has failed. (Ford Cars and Trucks reference to step
6 - all other cars reference step 7 and 8) With a flashlight inspect the
brackets and pulleys that connect the alternator, air conditioner
compressor, power steering pump, and air pump if equipped to the engine.
Look for signs of rust, this indicates broken or loose metal parts rubbing
together which can generate
squeaks and ticking noises. Replace the failed bracket or pulley as needed
and recheck. If the bracket is ok rotate each accessory by hand to check for
hard spots or seized bearings in the accessory and replace as needed.
Check Multi Rib Belt and Accessory Video
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Step 3 - Engine making a Rattling, Knocking or Tapping
Sound (upper engine noise) -
If you hear a lighter tapping
noise from the upper half of the engine, shut the engine off and remove the
valve covers. A
camshaft is commonly used to operate poppet valves in a
piston engine.
A cylindrical rod is situated in
the cylinder block or cylinder head that has oblong lobes or cams which push
open the intake and exhaust valves. This force is applied on the valve
directly or through an intermediate mechanism such as a rocker arm, lifter
(cam follower) and push rods that are used to press against the valve for
movement. Each valve utilizes a spring that will return the valve to its
original position (closed) after the force is removed. If a valve spring has
broken or a cam lobe is worn down it will cause the engine to create a
tapping or clicking sound. To test for this condition, remove the
ignition coil connector,
ignition system or
fuel pump fuse to disable power
to the ignition or fuel system. Remove the valve covers to gain access to visually
inspect the valve train.
Have a helper crank the engine
over while you watch the rocker arms or cam lobes, make sure they are all
going up and down the same amount, if one or more lobes are traveling less
than the others you might have a flattened cam lob and the camshaft needs to
be replaced or a hydraulic lifter/follower (where applicable) that has
collapsed and will need to be replaced. Also inspect the condition of
the valve springs, use a flashlight and small mirror to aid in the inspection
if needed. If a broken valve spring is discovered it will need to be replaced
to correct the problem. And the final check, look at the height of the valve
springs and retainers when in the closed position (pressure off) they should
be exactly the same height. If one valve is higher or lower something is wrong
with the cylinder head, valve or valve seat and needs to be repaired.
Typical Camshaft Configuration
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Step 4 - Engine making a Rattling, Knocking or Tapping
Sound (lower engine noise) - If a heavier noise seems to be generated
from the lower half of the engine the problem can be more serious and disassembly
maybe required. But, sometimes a lower engine noise could be generated due to
excessive carbon (carbon is a natural by-product of the combustion process)
build up on top of the piston. This noise is created when carbon is compressed
between the piston and the cylinder head. If you elect to perform a de-carbon
procedure start and run the engine until warm, have a helper hold the engine
at about 1500 RPM. As the engine is running poor a small amount of water down
the throttle body, about a cup, you are creating a steam cleaning effect to
break up the carbon that will exit the engine. Don't worry if steam is generated
from the
exhaust during the treatment, this is normal. If noise is gone after
the treatment the carbon has been removed, if the engine noise is still there
lower engine disassembly is required.
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Step 5 - Engine Humming or Honking Noise, (Ford Cars and Trucks Only)
- The
IAC motor (idle air control) controls idle air to the engine.
This process enables the computer to adjust idle engine idle speed. Ford has
manufactured an IAC motor (idle air control) that creates a loud humming sound,
almost like honking when it fails. If your engine is generating this noise replace
the IAC with a new unit and recheck system.
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Step 6 - Engine Squeaking or Chirping Noise with the Multi Rib Belt
Removed, (Ford Cars and Trucks Only) - Ford V6 and V8 engines only
with a CAS (cam angle sensor). Starting in the 90's ford started to manufacturer
engines equipped with a CAS. This sensor assembly is basically a distributor
housing with a sensor and trigger plate mounted to a center shaft. This center
shaft is driven by the camshaft. The problem is, Ford slowed the oiling to the
distributor housing and this causes the housing to seize to the center shaft. The
CAS seizes due to lack for oil making a high pitched squeaking noise, like a
loose belt. To check for this condition remove the drive belt and restart the
engine. If the noise is still there suspect the CAS, remove the unit and (by
hand) spin it. If the unit has failed it will be rough to turn, either dissemble
the unit to clean or replace the CAS housing with new.
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Step 7 - Engine Making Noise From the Front - Squeaking, Tapping or Chirping
Noise with the Multi Rib Belt Removed - Some engines are
manufactured with a timing belt. This belt is used to keep the crankshaft in 2 to
1 correlation with the
camshaft. This belt is kept under tension by the belt tensioner. This belt tensioner is constructed with a bearing that sometimes
can fail, creating a squeaking noise or chirping sound. Also when this tensioner
or timing belt starts to fail it can cause the timing belt to misalign. This
condition will cause the timing belt to shred producing ticking/scraping noises inside
the timing belt cover. If you are not sure your car has a timing belt, visit
this page:
timing belt diagrams
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Step 8 - Engine Making Noise From the Rear - An engine flex-plate
is used in
automatic transmission cars. It is used to connect power form the
engine to the
torque converter
of the transmission. When a flex plate fails it usually cracks at the
crankshaft mounting bolts. If the flex-plate is cracked it will make little
to no noise at idle, and make more noise depending on how much load the
engine is under. The more throttle that is applied the louder the noise will
become.
To check for this condition remove the flywheel inspection plate or cover. Using
a small flashlight and mirror, check for signs of rust dust near or around the
bolts. Rust dust indicates broken or cracked metal on metal contact. It is these
cracks flexing back and forth that generate the ticking noises. Once this condition
has occurred the only way to repair the problem is to replace the flex-plate.
This requires removing the transmission from the engine.
For exact specific repair procedures for any of the steps above visit our
online repair
manual page.
WARNING! Always have the vehicle under inspection on level
ground, in park with the emergency brake on. Always wear protective eyewear, gloves
and necessary clothing before inspection or work begins. Never crank an engine over
when anyone is near the battery or engine. Always have an operational fire extinguisher
close by, obey all first aid instructions in the event of an injury. Never stand
in front or behind a vehicle when starting or running. When engine is cranked over
keep hands and clothing away from rotating components. Anyone with a heart pacemaker
should not perform these tests.
Troubleshooting
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Why Does My Engine Make Noise
Additional Resources
Check Manufacturer Specific Engine
Noises Questions and Answers
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