Mechanics

Engine Scraping Noise

Easy step by step guide on how to repair an automotive engine scraping noises, this information pertains to most vehicles.

Difficulty Scale: 4 of 10

Begin with the vehicle on flat ground, in park with the emergency brake "ON" and the engine "OFF".

Step 1 - A bearing style of support pulley is used to keep tension on the serpentine belt, these bearings can fail causing a scraping noise which follows the engine speed. Learn more


Serpentine Belt Tensioner Bearing

Step 2 - A starter motor utilizes 12 volts to crank the engine over, when the starter motor fails it can allow the armature to contact the case which produces a scraping noise. Learn more


Removing Starter Motor

Step 3 - For manual transmission vehicles a throw out bearing is used to disengage the engine from the transmission. When this bearing fails it will cause a scraping noise either while the pedal is depressed or released.


Clutch Pedal Released

Step 4 - A harmonic balancer is used to quiet the vibration of the engine while running, when it fails the outer ring will separate from the hub causing a scraping noise that changes with engine speed. Learn more


Failed Harmonic Balancer

Step 5 - An ignition distributor is designed to distribute the ignition spark to each cylinder at the correct time and is constructed with a bearing. When this bearing fails it allows 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.

Helpful Information

A scraping sound is typically created when metal is contacting metal during linear or rotational movement. Rotating objects are generally prone to scraping noises because they have close tolerances and are positioned near stationary objects. Some scrapping noises are easily fixed by re-positioning a particular brace or shield, while bearing failures need to be replaced.

AUTHOR


Written by
Co-Founder and CEO of 2CarPros.com
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


COMMENTS TO THIS ARTICLE


Please use our question form if you have a specific question about your car as we are not able to give you a full answer on this page.



Article first published (Updated 2015-03-12)