Step by step troubleshooting instructions on how to fix abnormal engine noises.
This article pertains to all non electric vehicles.
Difficulty Scale: 4 of 10
Tools and Supplies Needed
- Small mirror
- Protective eye wear and gloves
- Wrench and socket set
- Hydraulic jack w/stands
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. Fuel injectors also make a slight clicking noise when the engine is idling.
These noises are normal and no repair is required, but if unexplained noises exist,
the following steps are the most common causes.
- Check the engine oil level, an engine
depends on clean oil to lubricate the internal moving parts, if the oil level is
low or 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 fail which will allow excess valve
train clearance creating engine tapping or clicking noise. 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 (viscosity) oil sometimes helps. Visit -
- A squeaking noise could be generated by
the engine accessories, accessory mounts, serpentine belt 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 serpentine belt
and start the engine. Visit -
If the sounds disappears an accessory, accessory bracket, belt or pulley has
failed. With a flashlight inspect the brackets and pulleys that connect the alternator,
air conditioner compressor, power steering pump, and air pump if equipped. 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 or a seized
- If a tapping or ticking noise from the
upper half of the engine remove the valve covers. Each valve utilizes a spring that
returns it to its original position, closed. 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
due to the excess clearance. 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. 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 (where applicable)
has collapsed and will need to be replaced. Also inspect the condition of the valve
springs, using a flashlight and a small mirror to aid in the inspection to look
for broken springs. If a broken valve spring is discovered replacement is required
to correct the problem. When checking valve springs look at the height of the valve
springs and retainers in the closed position, they should be exactly the same height.
If one valve is higher or lower something is wrong with the cylinder head the valve
or valve seat and needs to be repaired.
Replacing a Camshaft
Step 4 - If a heavier noise seems is being generated
from the lower half of the engine, the problem can be more serious and may need to be disassembled. But, sometimes a lower engine noise could be generated due to excessive
carbon, (carbon is a natural byproduct of the combustion process which builds up
on top of the piston.) 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.
Step 5 - Some engines are manufactured with a timing
belt. 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 noise
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/scraping noises inside the timing belt cover.
Step 6 - A flex plate is used in automatic transmission
applications. Its 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. 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 a break or crack. Its these cracks
flexing back and forth that generate the ticking noises. Replacing the flex-plate
requires removing the transmission.
Step 7 - 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.
Step 8 - Some engines are equipped with a cam
angle sensor. This particular sensor is basically a distributor housing with a sensor
and trigger plate mounted to the center shaft. If the sensor seizes due to lack
of oil a high pitched squeaking noise will be produced. To check for this condition
remove the serpentine belt and restart the engine. If the noise is still present
suspect the sensor housing.
Today's engines have been designed with more complexity and moving parts than
ever before. Most of the time when you hear abnormal noises there is something going
wrong. Excess 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 the engine, either the upper half, lower
half, front half or rear half. (note: 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 to 5,000 miles
with normal motor oil, and 6,000 to 8,000 miles with synthetic oil.
Article first published 2016-11-26