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 - KC

    2006 Trailblazer 4.2 inline 6 has started making a tapping/clacking noise it starts about 15-20 min. after I start it then at idle it will start soft then get louder the stop then start soft and then get louder and it keeps doing this.If I take the rpm up to around 2000 then it sounds like a sharp clacking noise.When I shout off engine I can hear what seems to be something dropping in the engine???

  • Guest - KC

    Her is a link to Youtube I posted video of the engine sound.<br /><br />http://youtu.be/ABzWUrhlgT0

  • Guest - Techjk

    In reply to: Guest - KC

    If you have done any work recently, it sounds like there is something bouncing around in the cylinder. If no work done you may have a broken valve spring. If it goes away sitting at idle in gear, i would check for a broken flywheel, even if it sounds like it is coming from the top of the engine- noise travels.

  • Guest - KC

    Took valve cover off and didn't see anything that looks bad turned engine over everything looks to be ok only thing is very slight play in one of the cam gears.I'll check flywheel if not probably in the bottom of engine.I got a stethescope and the sound seems to be loudest at the bottom in the oil pan.

  • Guest - Techjk

    Bottom of oil pan means either a bad main or rod bearing or crancked flywheel.

  • Guest - Km

    I have a 2007 cobalt that has sat for over a year because I believe the motor is going on it. It is making a knocking sound when you press on the gas. This car was in a car accident as well but was still in driving condition until the knocking. I'm trying to see if it is worth me trying to fix or if I should just get what I can get for it? What would be a reasonable price to give?

  • Guest - Techjk

    In reply to: Guest - Km

    :-? That is impossible to say what the car is worth wiothout seeing it.

  • Guest - Alan

    2003 Chevy 4.3 engine manual trans. Driving to work with no problems then about of the blue started making loud noise I can't described , but If I had to say.... A bunch of hammers hitting or banging around in a dryer. So loud beyond knocking. It died at a stop light. It will start easily but shakes and runs like crap. No warning signs at all. Wasn't overheating or leaking that I could see . Possible broken valve or blown engine ? It's been a great truck want to repair it. Need to know if I need to buy a new engine, or what. Please help.

  • Guest - Tom

    In reply to: Guest - Alan

    Sounds like the engine is blown. It threw a rod or broke a piston.

  • Guest - james

    have a 98 sunfire 2.2 used liquid glass to fix head gasket changed the oil needs done again water still mixed in oil but now my valves are ticking why??? please help

  • Guest - Mike

    In reply to: Guest - james

    Don't use liquid glass !

  • Guest - Nathan Hurley

    i have a 1997 buick lesabre has a bad nock and gets worse when you accellerate the oil preasure is normal when i first start it then after it gets warm it drops slowly to no oil preasure please tell me is it the oil pump or rod bearing or what

  • Guest - Tom

    In reply to: Guest - Nathan Hurley

    Yes, sounds like worn out bearings.

  • Guest - Mike

    I have a 1998 chevy blazer 4.3 vortec i was driving then stalled started up and have heard knocking noise check egine light came on 2 days later check engine light is off driving good but still here slight knocking can it be a knocking sensor or bad gas thankyou for any help

  • Guest - Tom

    In reply to: Guest - Mike

    Get the codes scanned. If the knock sensor is hearing a knock, then you need to get the engine fixed.

  • Guest - Chandler

    I have a 2001 Saturn Sl2. Today coming home i went to make a right turn and my car began to thunk and then i lost all power to my wheels. trany fluid is leaking out and i cant seem to figure out did i blow my trany or is it my cv joint. any ideas?

  • Guest - Tom

    In reply to: Guest - Chandler

    Get a mechanic to drive it.

  • Guest - aaron

    Truck hit a bump real hard and starting knocking and died and wont start its a 94 dodge dakota v6 4x4can u call me? 816 2947101

  • Guest - Bill

    In reply to: Guest - aaron

    A bump should not cause the engine to stall or knock unless it had no oil in it.

  • Guest - jesse

    have a 89 ford tempo, great condition, 145,002 kms. when put into drive and begin to accelerate I hear a slight knock. I hear this then going from reverse to drive or and time when going over speed bump, hitting the breaks when coming up to red light as well as acceleration.. I figured engine mount. there is 3, front, right front and tranny/motor mount. any other ideas, plz and thankyou

  • Guest - Harry

    In reply to: Guest - jesse

    A motor mount would have been my first thought as well. But reading your problem, it almost sounds like a suspension problem. Check the tie rods, control arm bushings and strut rods.

  • Guest - suleiman

    my car drips oil...it makes a creepy sound in the engine...it also brings out too much fumes from the exhaust pipe...please help. What could be wrong?

  • Guest - Harry

    In reply to: Guest - suleiman

    Your kidding right? You want us to tell you what is wrong with your car that drips oil, creepy sound, and smells ? REALLY !<br />How about this- you need to have a mechanic look at it, replace the engine, or get a new car !

  • Guest - JamesM

    In reply to: Guest - suleiman

    That's a bit too vague to say anything for sure, but it sounds like it could be either a cracked engine block or blown head gasket. I am no professional though. You should have a mechanic take a look.

  • Guest - James

    I have a 2003 honda civic lx, i heard knocking sound everytime i begine to move backwards and there is a unusual sound when i shifting from 3rd gear to 2nd gear or when it was on engine breaking. HELP! Service center cannot identify the problem!

  • Guest - Tom

    In reply to: Guest - James

    I have a 2003 honda civic lx, i heard knocking sound everytime i begine to move backwards and there is a unusual sound when i shifting from 3rd gear to 2nd gear or when it was on engine breaking. HELP! Service center cannot identify the problem!
    <br />Check engine mounts and transmission.

  • Guest - Sarah

    I have a 2001 chevy prizm and every time I start my care before its warmed up it makes a knocking sound when I shift from park. Does anyone have an idea what this could be?

  • Guest - JamesM

    I have a 1990 Chevy S10 with a manual-transmission. It makes a kind-of ping/knock (but more of a ping) whenever I put it into gear, take it out of gear, hit the gas or let off the gas and at some other random times too, but only when the truck is rolling. Any ideas?

  • Guest - Trey

    I have a 99 Chevrolet silverado. Lately, when I accelerate from 0-15 mph the engine sounds "loud" like the rpms should be high (but they aren't). Once I get above 15-20 mph, everything sounds normal. Any idea? I really appreciate your help.

  • Guest - Juan

    I got a 2005 Chevy Silverado I open up the heads remove the knock sensors cap off and find out the timing chain sprocket was really lose Would that cause it to lose your Oilpressure

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