Engine Noises | Knocking and Ticking | Common Causes

Main Bearing Noise

Damaged or worn main bearing noise is revealed by dull thuds or knocks which happen on every engine revolution. This noise is loudest when the engine is under heavy load. Excessive crankshaft end play is indicated by an intermittent rap or knock sharper than a worn main bearing.

The following are causes of main bearing noise:

 

  • Low oil pump pressure
  • Thin, diluted or dirty oil and/or filter
  • Excessive main bearing clearance
  • Excessive crankshaft end play
  • Out-of-round crankshaft journals
  • Loose crankshaft pulley
  • Loose flywheel or torque converter
  • Loose main bearing cap

Connecting rod Bearings

A damaged or worn connecting rod bearing will produce knock under all speeds. During the early stages of wear, connecting rod noise may be confused with piston slap or loose wrist pins. Connecting rod knock noise increases in volume with engine speed and is at its loudest on deceleration.

The following are causes of connecting rod bearing noise:

  • Excessive bearing clearance
  • Worn crankshaft connecting rod journal
  • Thin, diluted or dirty oil and/or filter
  • Low oil pressure
  • Crankshaft connecting rod journals out-of-round
  • Misaligned connecting rod
  • Connecting rod bolts not properly torqued
  • The wrong bearing inserts or misaligned bearing half


Timing Chain and Gears

Engines designed with timing gears, or those equipped with a timing chain and sprockets, can produce different noise. The most common noise is a high frequency, light-knocking sound. This sound will generally be the same in intensity whether the engine is idling, operating at high speeds, or under load.

The following are causes of timing gear or chain and sprocket noise:

  • Worn timing chain and/or gears
  • Misaligned gears
  • Excessive backlash
  • A damaged tooth
  • Gear or sprocket loose on the shaft
  • Too much end play in the camshaft or crankshaft

Loose or improperly seated camshaft timing gears are usually loudest when warm. They are speed sensitive only. They are not load sensitive.

Cam gear noise will usually be evident at a warm idle in neutral and sounds much like a loose timing chain noise.

Piston Noise

Piston pin, piston, and connecting rod noise are hard to separate. A loose piston pin, for example, causes a sharp double knock usually heard when the engine is idling, or during sudden acceleration then deceleration of the engine. A piston pin that has been improperly fitted will emit a light ticking noise that is more noticeable with no load on the engine. Excessive piston-to-cylinder bore clearance will cause piston slap noise. The noise is similar to a metallic knock, as if the piston were "slapping" the cylinder wall during its stroke. As with most engine noise, understanding the cause of the noise will help you imagine what the noise sounds like. An indication of piston slap is a decrease in noise as the engine warms up. When the engine is cold, the piston to bore clearance is greater and piston slap will be louder.

Flywheel Noise

A loose or cracked flywheel will produce an irregular thud or click. To test for a loose or cracked flywheel, operate the vehicle at approximately 32 km/h (20 mph) and shut off the engine. If a thud is heard, the flywheel may be loose or damaged. This type of thud is loudest on deceleration. Loose torque converter-to-flywheel or flywheel-to-crankshaft bolts will sound similar to bearing knock. This condition produces several raps during quick acceleration on a free running engine. Depending on the idle smoothness, when the transaxle is in gear, the noise may or may not appear. Check the torque converter-to-flywheel and the flywheel-to-crankshaft bolts before attempting to investigate any bearing-related knock.

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  • Guest - Beverly

    I have a 2007 Ford Taurus SE; After the car starts there is a low growling sound, when the car is moving and I start to accelerate it then turns into a whine; by the time I going 65-70 mph its a high pitched whine! Almost sound like the car is stuck in gear or between gears!! You know what I mean?

  • Guest - Beverly

    I did notice that before the noise started when I was going up a steep incline, then my engine light would flash on and off; the engine light would not stay on just flash on and off; then about 2 weeks later the noise started. I had just recently had the car serviced and there is 115,000 miles on it.

  • Guest - Mechboy

    In reply to: Guest - Beverly

    A flashing engine light means an engine misfire. The noise could be a front hub bearing.

  • Guest - traking

    I have a 1998 Chevy Z71 truck -- I just drove it 300 + miles - all ran good then two days later a hose busted - fixed it. Now I crank it and there's knocking sound coming from engine? what could it be? is it ok to drive 20 miles to mechanic? there no oil pressure on gauge but oil on the stick when I check it. it has 183,000 miles.

  • Guest - Mechanic Paul

    In reply to: Guest - traking

    No oil pressure means DO NOT DRIVE IT. Oil on the stick is just the level of oil, not the pressure. Have it towed.

  • Guest - Andy

    I have high oil pressure and a ticking sound on a mondeo zetec, I'm guessing blocked oil way/filter and it's the pressure release valve ticking?

  • Guest - Jerry c

    Hello!<br /> I have a 2004 chevy impala when I started up and the eengine is cold it makes a low knocking sound I've heard that its normal but I want to know if it's normal or nor not please thank you

  • Guest - Bobby

    In reply to: Guest - Jerry c

    On the 3400 engine, a slight knocking is normal. It is called Piston Slap. On the 3800, no noise is normal.

  • Guest - twitty

    Have a 07 5 speed caliber a knock noise has just starter it runs engine is quiet but when a press peddle the knock starts up and go some what away. When i am inbetween shifting it sounds like a more of a hollow knock from the back of the engine firewall area when rpming down to shify to next gear. What gives

  • Guest - Ted

    In reply to: Guest - twitty

    Have a 07 5 speed caliber a knock noise has just starter it runs engine is quiet but when a press peddle the knock starts up and go some what away. When i am inbetween shifting it sounds like a more of a hollow knock from the back of the engine firewall area when rpming down to shify to next gear. What gives
    <br />What? You got an engine knock. I think. Cant understand a word you are saying !

  • Guest - duane hartley

    In reply to: Guest - Ted

    put in some buster octine if nois stops it is spark knock

  • Guest - Wil

    I have a 2006 buick lucerne. i have started to hear a wineing sound from the car as you drive faster does not do it at a stop and idle. and gets louder as you drive. what could ot be?

  • Guest - Ted

    In reply to: Guest - Wil

    Check your power steering fluid and transmission fluid if it is engine speed related. If it is car speed related, may be a noisy front hub bearing.

  • Guest - joe castillo

    I have a 2005 Chevy Tahoe all the lights turn on but when I turn the key to turn it on it makes a loud clicking sound. It don't start or anything. I passed cables nd still no response. What could it possibly be.

  • Guest - Ted

    In reply to: Guest - joe castillo

    A loud clicking is the starter trying to crank the engine. Either hte starter is bad, or the battery is weak. just because the lights are on does not mean it has enough power to start the truck.

  • Guest - SLM

    1999 oldsmobile alero V6 knocking noise started a while ago, noise is consistent during driving, acceleration, stopping, etc, but has gotten louder over time...?

  • Guest - Ted

    In reply to: Guest - SLM

    1999 oldsmobile alero V6 knocking noise started a while ago, noise is consistent during driving, acceleration, stopping, etc, but has gotten louder over time...?
    <br />Check for a coolant leak from the intake manifold causing the oil to look like a milkshake.

  • Guest - jharris

    my 2000 f-350 gas truck is missing when i press the gas does not do this when not pressing the gas sounds like it suppose to

  • Guest - Ted

    In reply to: Guest - jharris

    That is the sign of an ignition problem. Probably a bad spark plug or plug wire.

  • Guest - Brett

    My 1998 S10 was making a knocking sound when I would it accelerate the knocking would get louder.. The next day it got louder and I went to take of from a stop light and only got like 15 feet and then I stopped running.

  • Guest - Tony

    In reply to: Guest - Brett

    Sounds like your engine is now locked up. Either low oil pressure was what started it, or just a worn out motor.

  • Guest - trina smith

    Ihave a 2005 booneville and when I start it upto let it warm up it knocks for like 5 mins

  • Guest - duane hartley

    sounds like a valve lifter

  • Guest - Julio torres

    My brother in law has a 2004 ford expedition he recently changed the oil and spark plugs them the motor started knocking could he have done something that caused this while doing what he did.

  • Guest - Tony

    In reply to: Guest - Julio torres

    My brother in law has a 2004 ford expedition he recently changed the oil and spark plugs them the motor started knocking could he have done something that caused this while doing what he did.
    <br />Not unless a spark plug broke and part of it fell into the cylinder.

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