Abnormal engine noises are trying to tell you there is a problem
are designed with more complexity and moving parts than
ever before. When you hear abnormal noises there is something wrong. Some high
output engines have short skirt pistons or roller valve trains so a minimal
amount of ticking is normal when the engine is at idle. Fuel injectors also make a slight clicking noise when the engine is idling
as well. These noises are normal and no repair is required. If unexplained noises exist
the steps below are the most common causes.
What Goes Wrong?
Abnormal engine noise is due to excessive clearance between two internal metal
parts that should have little to no clearance. This clearance can be due to many
things from a broken valve spring to a crankshaft bearing that has failed. The first
step is to identify where the engine noise is being generated. With the engine running
isolate where the noise is coming from in either the the upper half, lower
half, front half or rear half. Listen from above and below the engine as this will help determine where to start looking for the cause of the noise.
Let's Get Started
1. Check Engine Oil
An engine depends on clean oil to lubricate the internal moving parts. When
the oil level is low or dirty it can cause the lifter to malfunction which will
allow excess valve train clearance creating a tapping or clicking noise. For example:
A valve lifter is responsible for holding valve train clearance to a minimum. In extreme
cases it can cause one of the many bearing surfaces to fail causing permanent
engine damage. An engine making a slight noise
changing the engine oil and filter
with the manufacturers recommended weight oil will help.
2. Engine Front Squeak or Ticking Noise
A squeaking noise is generally created by the engine accessories, accessory mounts, serpentine belt or drive pulleys. When
an accessory such as the
power steering pump
serpentine belt tensioner
or idler pulley has failed it can make a
squeaking or tapping noise. These sounds are centrally located near the front of
the engine. With the engine off check the tension of the serpentine belt. 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 serpentine belt
and start the engine to see if the noise is still there. If the sound disappears
one of the above items has failed. With a flashlight inspect the brackets and pulleys that connect the alternator,
air conditioner compressor, power steering pump, and alternator. Look
for signs of rust (reddish powder). This indicates a broken or loose metal part
rubbing together which can generate squeaks and ticking noises. If the brackets
look okay rotate each accessory pulley by hand and check for hard spots
indicating a seized bearing.
Some engines are manufactured with a
. This belt is kept under
tension by the belt tensioner. The belt tensioner
is constructed with a bearing that can sometimes fail creating a squeaking
or chirping sound. Also, when this tensioner or timing belt starts to fail it can
cause the timing belt to be misaligned. This condition will cause the timing belt to
shred producing ticking or scraping noise inside the timing belt cover while the
engine is running.
3. Inside the Engine
If a tapping or ticking noise is coming from the upper half of the engine
remove the valve covers
This condition is sometimes accompanied by an
. Each valve utilizes a spring that
returns it to its original closed position. If a valve spring has broken or a camshaft
lobe is worn down it will cause the engine to create a tapping or clicking sound
due to the excess clearance.
To test for this condition disable the ignition system or fuel pump by
removing the system fuse. Have a helper crank the engine over while watching the rocker arms
or cam lobes making sure all valves are traveling the same amount. If one or more
lobes are traveling less than the others the engine has a flattened cam lob and
the camshaft needs to be replaced or the hydraulic lifter/follower has collapsed and will
also need to be replaced.
Look for broken springs using a flashlight and a small mirror. If a broken valve spring is discovered replacement is required
to correct the problem. When checking valve springs compare the retainers in the closed position they should be exactly the same height.
If one valve is higher or lower something is wrong with the
valve or valve seat and removal is required.
4. Piston Carbon
If a lighter knocking noise seems to be generated from the middle part of the engine
it could be generated due to excessive carbon build up on top of the piston. This carbon is a natural byproduct of the
combustion process which builds up on top of the piston is some cases. This
knocking noise is created when carbon is compressed between the piston and the
cylinder head. To repair this problem the cylinder head needs to be removed or
the engine needs to be subjected to a de-carbon process which can be done by
pouring a steady stream of water down the intake of a hot engine at
about 3,000 PRM. This will break up the carob and allow it to pass through the
5. Noise at Engine Rear
A flex plate is used in automatic transmission applications and 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. This will
make little to no noise at idle and make more noise depending on how much load
the engine is under. As more engine power is applied the louder the noise will
become. To check for this condition remove the flywheel inspection plate or
cover. Use a small flashlight and mirror check for signs of rust dust
near or around the bolts. Rust dust indicates a break or crack. It's these cracks
flexing back and forth that generate the ticking noise. Replacing the flex-plate
removing the transmission
6. Engine Humming or Honking
The IAC motor (idle air control) controls
idle air to the engine. When an IAC motor fails it creates a loud humming sound
when it fails. This is a common problem with Ford engines meaning
idle air control motor
needs to be replaced.
7. Engine Knocking
When there is a deep knocking noise coming from within the engine toward the
bottom it means there is a broken piston, seized wrist pin, rod bearing or
crankshaft bearing that has worn or gone bad. To fix this problem the engine
must be disassembled and repaired.
Got any Questions?
If you have any
engine noise questions
please visit our forum. If you need
, please ask our community of mechanics is happy to help you and
it is always 100% free.
We hope you enjoyed this guide. We are creating a full set of
car repair guides
subscribe to our 2CarPros
channel and check back often for new videos which are uploaded almost
Article first published 2017-02-03