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Car Noises /
Scraping Noise
My Car is Making a Scraping Noise
Introduction
A scrape or scraping sound is typically created when metal is contacting
metal during linear movement. This condition can be created by a bearing that
has failed or a brake heat/dust shield that is out of place. Scraping sounds
generally do not occur from the
engine,
transmission
or
differential. Rotating objects are generally prone to scraping noises
because many components have close tolerances and are positioned near objects
that are not moving. The first step is locating the region in which the scraping
sound is be generated. Some scrapping noises are easily fixed by repositioning a
particular brace or shield while bearing failures need to be replaced. Other
scraping sounds are activated when the key is brought to the crank position such
as the
starter motor. We have list common problems below:
Scraping Noise
Car Repair Guide - READ COMPLETELY BEFORE BEGINNING!
Engine Running, Car Not Moving: This section includes
symptoms that present themselves when the engine is running only.
- Check Engine Accessory Mounting/Condition: When your
engine starts it provides power to various accessories such as the
water pump,
power steering,
air
conditioner,
alternator,
and air pimp (if equipped) These accessories are held in place by mounting
brackets while being the inner working are supported by a roller bearing. If these roller bearings fail they can allow the
impeller or armature to contact their respective housing. To check
for this condition start with the engine off, then remove the multi rib belt
and rotate all accessories by hand and check for resistance and lateral
play. If either of these conditions is present replace the component in
question and recheck system. Removing your car's multi rib belt is a relatively simple repair that can
be done in a few minutes with minor tools in most cases. Always wear protective
gloves and eyewear before you begin.
Change Multi Rib Belt Video
-
Starter Motor Scraping Sound: The
starter motor is designed to crank the engine over by engaging onto the
engine flywheel. This starter motor has bearings that can fail allowing the
armature to contact the starter motor housing which contain cylindrical
magnets. These magnets are dense and can make a very generous scrapping
noise when the starter is activated. If this noise exits when the engine is
cranked over the starter motor has failed and replacement is required.
-
Checking a Throw Out Bearing (standard transmission vehicles only):
A throw out bearing is designed to press against the
clutch pressure plate. This bearing is what rides near the pressure
plate and is activated when the clutch pedal is depressed. If a scraping
noise is heard when the
clutch pedal is depressed this bearing has failed and replacement is
required.
Typical Clutch Pressure Plate, Disc and Throw-out Bearing
-
Inspecting an Ignition Distributor: The
ignition
distributor in your car is designed to distribute the ignition spark to each
cylinder at the correct time. This distributor is constructed with bearing
that can fail allowing the main distributor shaft and stator to contact the
stationary housing and pick up coil(s). When this condition occurs it can
cause the engine to stall, and then start again once the engine has cooled
down. To check for this condition remove the distributor cap and check for
lateral movement in the main shaft. Also this condition is sometimes
accompanied by rust colored powder in and around the interior of the
distributor housing. If this condition has occurred distributor replacement
is required in most cases. This problem is especially inherent in
Honda motor cars.
-
Scraping Noise When Air Conditioner is On - The
air
conditioner is designed to operate using a electromagnetic clutch
assembly that receives a command signal from the activation switch. This
command controls when electricity is supplied to the compressor clutch that
engages and disengages the air conditioner system. If the air conditioner
compressor has failed it can cause a scrapping sound when the air
conditioner is switched on. Once the system has been switched off the noise
will stop, if this is the case with your cars the air conditioner
compressor replacement is required.
-
Inspect Harmonic Balancer: The
harmonic balancer on your engine is used to help silence engine
vibration by utilizing a rubber mounting metal ring attached to a hub that
is connected to the front of the engine. If this ring becomes dislodged
because the rubber insulator has failed it will allow the outer ring to
bounce and scrape on the rotating hub. This condition will produce a
scraping
noise that will change with engine speed. To check for this condition
remove the multi rib belt and check the harmonic balancer condition. If
the outer ring is lose replacement is required.
Failed Harmonic Balancer
Engine Running, Car Not Moving: This section includes
symptoms that present themselves when the engine is running only.
Car Moving: This section includes symptoms that present
themselves when the car is in motion
- Loose Brake Caliper: The
brake
pads and calipers are designed to slow the vehicle when applied. The
brake caliper holds these brake pads that are applied to the
brake
rotor. If the caliper is lose because the main caliper mounting bolt(s)
are
missing it will allow the caliper to ride against the inside of the rim
producing a scraping noise. To check for this condition
inspect the brake caliper mounting bolts to make sure they are tight and
intact. If these mounting bolts are missing replace and tighten with new.
Do not drive the vehicle in this condition, brake
operation failure can occur.
How to Change Front Brake Pads and Rotors
- Worn Out Brake Pads or Shoes: The
brake
pads on your car are designed to slow the vehicle when applied. If the brake pads are
completely worn out they will can create a scraping noise when the brakes are applied.
This scraping noise is created when the pad is forced against the brake rotor
in normal braking operation. To
check for this condition inspect the brake pads in question. The brake pads
should have composite material between the pad backing plate and the
brake
rotor, or on the rear of the
vehicle
brake drum and
shoes. If a brake grinding noise is allowed
to continue, brake operation failure could occur. The
rotor featured below is a perfect example of what can happen if a brake
grinding noise is left unattended.
Scraped Brake Rotor
When a scraping brake rotor is neglected, it will cause the brake
system to fail due to the separation of the rotor hat (center) from the
outer web (braking surface). Additional problems can occur include the
brake pad to fall out completely or the
brake
caliper to blow out a piston. Either condition will cause brake
operation failure. Do not drive the vehicle in this
condition, brake operation failure will occur.
-
Relocate Brake Rotor Heat/Dust Shield: When the
brake rotor
is in operation it produces heat and the rotor is subject the road side dust
that can inhibit proper brake function. To help protect the brake rotor a shield
is fastened to the spindle. If this shield becomes slightly out of alignment it
can come in contact with the rotating brake rotor creating a scraping noise. To
check for this condition support the car to remove the wheel in question. Next,
rotate the brake rotor by hand to recreate the sound. Then inspect the air gap
between the brake rotor and shield, reposition as needed and reassemble.
-
Checking Axle Bearing Failure: An axle bearing is designed to
support the weight of the vehicle while allowing the wheels to rotate. These
bearings are manufactured with high grade steel that resists wear under
extreme conditions. When an axle bearing fails it allows metal to contact
metal under pressure with a linear motion creating a scraping noise. Once an axle bearing fails it cannot be repair, replacement is required. Remove
axle bearing and replace with new and recheck. Some vehicles are equipped
with a bearing hub assembly. The bearing below is the style of bearing is replaced by un-bolting
the bearing hub assembly and replacing it with new.
Axle Bearing Hub
Other bearing designs include separated bearings that include inner and
outer bearings with bearing races, a four piece set. Separated bearings
require an inboard seal attached to the bearing hub. This seal rides on the
spindle to hold grease inside of the bearing hub, keeping lubrication inside
of the bearings.
Axle Bearing/Race Set with Seals
-
Check for Tire to Body Contact: The tires on your car are
designed to rotate with a minimum clearance between the body and the wheel.
If this clearance is minimized by the wrong tire size or suspension
modification or failure it can allow the tire to rub against the inner
fender wheel which will create a scarping noise. To check for this condition
inspect the cleaner between the tire and inner fender well. Check the
suspension for spring failure or tire size to make sure the proper tires
have been installed.
For exact specific repair procedures for any of the steps above visit
our
car repair
manuals page.
Car Noises /
Scraping Noise
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