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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    Comments (232)
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    • Guest - serina

      i have a 98 chevy blazer i need a water pump for sue but my check gauges light comes on when i stop and the oil pressure drops all the way down now my truck is knocking please help me i dont know what is going on i think i just need pick up tube and oil pressure sensor what do yall think

    • Guest - Ernest p thomas

      Why my 2005jeep laredo4.7liter is taking tha water but comes back up.but I hear a knocking nose.i cut on tha air and then it ran hot on me.this is a new motor in this jeep just put it in two months ago cut on tha air for tha first time and it runs hot.what is it

    • Guest - Krystie

      I was extremely low on oil, I put oil in now my car is making a rattling roaring sound when I go above 20mph. It doesn't do it if I drive under 20mph. My check engine light starts blinking when I go above 20mph. What do you think this is?

    • Guest - jim johnson

      looking at buying a 2003 Chevy S10 4x4. SRLS model .. 155,000 miles, has not been running for 10 months. Just started it and has a knocking sound... Gas is spoiled in tank but did start. What can we put in it to improve gas quality? And one Cylinder has a low pressure output. I'm looking at buying this and getting it to a shop to repair. Most shops dont fix engineds they just replace. What are your thoughts. I'm buying at $1700 trade in value is $1400 to $2400. your thoughts would be appreciated,?Shoud i walk away with these issues or could it be a good opportunity to fix up for $500 and make some money

    • Guest - sabrina

      In reply to: Guest - jim johnson

      I have a GMC 3.0 engine went off the road 2 days ago now it as a knocking sound and when get up speed it starts shaking and if let gas off increase shaking even the stering wheel shakes Help

    • Guest - Tim

      In reply to: Guest - jim johnson

      I would walk away from this problem truck. You need to drain all the fuel, Low cylinder pressure means engine needs to come apart to fix it.

    • Guest - kathleen

      2001 buick regal gs just started making a ticking outside is over 100 .Engine part closest to drivers seat started smoking.Have heard reports of engine fires with this model.

    • Guest - Tim

      In reply to: Guest - kathleen

      The smoking is probably a leaking valve cover gasket. Ticking in that extreme heat could be a worn lifter, rocker arm or low oil pressure.

    • Guest - Celina Castellano

      Hey I need advice. I have a 1997 sc1 saturn 5 speed. It had issues keeping oil and I had the filter changed and drained. Since I've been running threw oil. Then a loud rattling began to happen from the engine .it happens when the car i s ideling in gear driving and even worse and louder when the gas pedal is pressed . , , i can smell a faint odor when it is ideling in neutral. Tinted white smoke comes from the exhaust. Checking the oil it is all still there. It burns threw quickly. The service engine light is on now and the sound is horribly loud.

    • Guest - Hey

      I have a 2006 dodge caravan an one day I was driving down the road and it sounded like something broke it kept going for a little bit but then died?? It started right back up but it was making a sing like something broke off in the motor or something. It made a really load clegging sound!! I need help I'm a single mom with no transportation

    • Guest - Tim

      In reply to: Guest - Hey

      You have major internal engine problems.

    • Guest - Atha

      My 2000 aluminum block has been ticking for years,but its louder ticking now. Whats this?

    • Guest - Seth

      I have a 87 Camaro engine 350 small block, it just started knocking and sounds like a diesel engine it's knocking so bad what is the prob.. note I just fixed the balancer yesterday

    • Guest - Sam

      I have an 06 ram. The other night I heard a clicking sound coming from the front as I accelerated. I pulled off to the side and shut it off. After that it wouldn't start for a little while. When I did get it to start, the engine shook and knocked violently, so I immediately shut if off. What could be going on with it?

    • Guest - Larry

      I have a 2007 Mercury Mariner V6. I started hearing this knocking noise and often times the car would stall. I changed the oil and replaced the spark plugs. But the issue continues.

    • Guest - Mick

      Have a toc toc noise when i put the vehicle in drive as soon as i put it in neutral its gone was wondering what it is .
      Any suggestions

    • Guest - Tim

      In reply to: Guest - Mick

      Possible cranked flywheel.

    • Guest - Karan

      I have a 07 Chevrolet hhr and i hear a knocking noise and it worsens when u hit the gas what could be the problem and it keeps shutting off

    • Guest - Monique

      I have 2006 ford taurus and my starter when out so I replaced it and it won't start but whe you try to turn it on there's a knocking sound coming from the top of the engine what could be wrong with my car please someone cuz that all I have to get home to az

    • Guest - Tim

      In reply to: Guest - Monique

      Possible broke timing chain.

    • Guest - Cheyne

      I just bought 03 dodge ram 1500 4x4 and when I start it up loud knocking and it doesn't go away it gets worse when I accelerate can u help

    • Guest - Tim

      In reply to: Guest - Cheyne

      A loud knock is very bad. Probably a bad main bearing.

    • Guest - Ann

      I recently bough a rouge. When i give it gas, it makes a ticking noise. Like a card hitting a running fan. It stops after a few moments when it warms up. It drives perfectly fine, what could this be? It has been 5 degrees outside for several days

    • Guest - Tim

      In reply to: Guest - Ann

      Sounds like a sticking lifter. They will make noise when a very cold engine and then free up when the engine warms up.

    • Guest - raul

      i ran into a big potwhole big enough for my car to fit and when that happen my car turn of basicly the whole motor got wet then i took it out try to turn it on but it wouldnt turn on then i charged my battery and it turn on but it started making a noise a knocking noise under the car but i cannt realy make it if its on top or the bottom what could it be so i can be sure of what im looking on spending on my car and find the cheapest way of doing it just if you can tell me what could it be please and thank you

    • Guest - Tom

      In reply to: Guest - raul

      Ig you ran into water that deep, most likely the engine has sucked in water and is damaged. Remove th air filter to see if it is wet. If it is, then water got inside the engine cylinders and the engine is damaged.

    • Guest - Malisa

      Have a 2001 chevy express 2500 and have a ticking noise only once engine is warm and only when accelerating. Sound coming from around oil filter what could it be

    • Guest - Dave

      My96 jeep v6 4.0 started making a ticking noise a cople days ago out of the blue ,,,no loss of oil pressure,,,at a loss as what to check

    • Guest - Sly

      My Chevrolet LT Astro always knocks bearings what is the cause?

    • Guest - Valerie

      Replaced my flywheel on a 1999 Chevy Tahoe 4x4, my starter is good, but when I try to start it, it still makes this loud rough clicking type noise. Had some try to start while I was looking an it's like the flywheel is stuck, doesn't want to move. Can you give me some idea or advice to what this might be? I really need the help, I'm a single mother with two young children an this is my only form of transportation. Thank you, Have a Great Day!

    • Guest - Tom

      In reply to: Guest - Valerie

      Not sure by what you mean the flywheel is stuck. It cant be. If the engine does not turn over, then either the starter is bad or the engine is locked up.

    • 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?

    • Guest - Phil

      In reply to: Guest - Rachael wilson

      Any ticking noise is bad. If the il was low for a long time, then there may be internal engine damage to a lifer, rocker arm or pushrod.

    • 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - shelly

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

    • 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 - cynthia

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

    • 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 ?

    • I never asked about noise

    • 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?

    • Guest - sam brittendall

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

    • Guest - Mary H

      my son ran into a road covered in water. The car immediately died. The next morning the car cranked but now has a knocking sound. the oil is clean and there is no water in the engine. will someone please help. I am a single mom and my son uses his car for part time wok and school.

    • Guest - markiss

      In reply to: Guest - Mary H

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

    • Guest - Vic's

      In reply to: Guest - Mary H

      Did figure out what happened

    • Guest - Vic's

      In reply to: Guest - Mary H

      That just happened to me. I ran through a puddle of water the car died and when I started it again there was a ticking noise

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