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 - Vic's

    In reply to: Guest - Mary H

    Did figure out what happened

  • Guest - markiss

    In reply to: Guest - Mary H

    He dry locked the motor... Its done....

  • Guest - sam brittendall

    can you put new rod bearings in a 2001 monte carol 3.8 engine with out pulling the engine

  • Guest - jr gonzalez

    I got 2005 chevy silverado 5.3 sometimes it knocks while driving i stop shut it off turn the truck off and the knocking goes away its starting to do it more often what could it be?

  • I never asked about noise

  • Guest - Bill

    i have a 2003 vw gti 24v vr6 golf and when it reaches higher temps it starts having a knock to it what could the problem be ?

  • Guest - cynthia

    I just rebuilt my Durango engine and I started it up and it rattles what could this possibly mean?

  • Guest - Jr

    In reply to: Guest - cynthia

    Means you did it wrong

  • Guest - Currie West

    If I buy a oil pump switch or a oil pump for a 1997 gov saffari mini van 4.3 will that stop a bottom end knock on the motor

  • Guest - Jr

    In reply to: Guest - Currie West

    No, if its knocking the damage is already done

  • Guest - shelly

    My car is tappin and hittn sound. What do i do

  • Guest - Jeremiah

    Loud tapping and knocking noise then my truck shut off and coasted to a stop. After and hour it did crank up again. What do you believe my problem is and is it fixable?

  • Guest - Noah

    In reply to: Guest - Jeremiah

    Hard to say with out some more info, but piston slaps/rod knocks are normally present when the car is not under load. This means when you hit the gas sometimes the knocking stops. What you can do to check this is pull spark plug wires one at a time while the car is running in gear (with the parking brake on). If you find the knocking stops when you pull a certain plug wire then it's probably time to rip apart the motor. Also a compression test wouldn't hurt in case it's just a sticking valve ( A cylinder with a stuck valve will have MUCH lower compression readings than the rest)

  • Guest - Todd

    I have an automatic mustang 98 Gt. I've felt and heard a loud thump under the car approx. in the area where tranny bolts to engine. Has done it parked and moving. 1 loud thump. Car seems to shift fine. No other noises. ?

  • Guest - Jr

    In reply to: Guest - Todd

    Check for a loose or broken flexplate.

  • Guest - Dallas

    1999 Ford Expedition has high miles on it it makes a knocking noise that's pretty loud only when its idling its in there but its just sitting still as soon as I put it into gear it stops making the noise what could it be

  • Guest - Phil

    In reply to: Guest - Dallas

    Possible a cracked flywheel.

  • Guest - David Jones

    I just had my engine rebuilt, when I crank the engine up when cold it sounds like a Diesel engine, after warming up its better, but I can still hear the ticking just not as bad. My question to you if I do nothing about this what ,and how long is the engine going to last? Also I have apox. 1500 miles on the rebuilt engine now and this is the 3rd oil Chang it looses 3 quarts of oil about every 500 miles. It's not smoking or leaking ,or blowing it, where is the oil going, and am I looking at a engine that not going to last? The shop that rebuilt it does not won't to do any thing about it.They charged me. $3750.00 what can I do it is making me sick.

  • Guest - Jr

    In reply to: Guest - David Jones

    Check your oil, and coolant see if the fluids have mixed. Possibly blew the head gasket. While oil can burn off, that much you would see it. Which means its going somewhere. Into the coolant system, out the air cleaner, or out the exhaust. If this happened just after a rebuild, your mechanic screwed up, and didn't put it together right.

  • Guest - Christine

    When i turn the truck on it make a knocking noise and clicking noise when i push on the gas .i have a 1999 hrand jeep cherokee larado.

  • Guest - chevynomore

    2014 Chevrolet Silverado crew cab 2wd has a tapping noise, stops after truck warms up, dealer says it's the starter shield, but they can't seem to make it stop, any suggestions

  • Guest - Phil

    In reply to: Guest - chevynomore

    Common problem on this Chevy motor. Cold engine tap or tick noise. They have had many procedures to try to fi it- new piston rings, oil pan with baffles, nothing seems to help.

  • Guest - Ralph Salazar Acworth , Georgia

    Have 93' Firebird TAKE , oil leaks or blows back thru oil caprunning down to exhaust .

  • Guest - Phil

    In reply to: Guest - Ralph Salazar Acworth , Georgia

    This is called blowby. You have internal engine problems. Most likely worn out piston rings or valve seals.

  • Guest - Alyssa

    I have a 2004 chevy trail blazer it just started to make a vibrating taping sound from the front I pulled over and the oil is good and it don't really make the noise when ur stopped but u can tell it is coming from under the hood but the engine light is not coming on

  • Guest - Bryan

    In reply to: Guest - Alyssa

    I have this same problem still trying to find out what it could be

  • Guest - Arnel

    i have Lancer 2009 model year manual transmission, my problem is when i drive the car shifting from first gear then to second gear i heard unusual sound like katak katak katak from my engine. what could be the problem on this. thanks..

  • Guest - Phil R

    I have a 2008 mustang gt. Had the engine replaced. New installed engine sounds perfect when cold, but starts a horrible knocking sound once the car is driven for 20 minutes. When the sounds happens and engine is turn off/on the sound goes away, but starts again once it goes under load on any gear. Sound is knocking increasing sound as if the engine was going to blow up. Was unsure if it was a possible transmission issue. Mechanic convinced the engine was bad.

  • Guest - Phil

    In reply to: Guest - Phil R

    Not a transmission noise. This is an engine noise or flywheel noise.

  • Guest - Rachael wilson

    I have a 95 GMC YUKON and just recently it started making an awful ticking noise. My first thought was to check the oil and it was low. Having put 2 quarts in it is still making the ticking noise. Any idea of what it could be?

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