Step 4 - If a heavier noise seems is being 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 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 misalign. 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.