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 (210)
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    • 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 - 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 - 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

    • Guest - Joel

      2001 regal making a loud clicking noise when driving eventually the noise happen when I started it for 2 days then try to start it it didn't start. Mechanic said it was flywheel n torque convertor said how did I tear it up like that the flywheel well he fixed it and 4,days later it made a loud noise when started cut if off didn't start again. Took it back said I broke the bolts off into the crankshaft then call back and said transmission. The car wouldn't start how he know its the trans and my trans wasn't slipping or anything like that. 3 months before that he put an engine in my car and I drove it a month with that loud noise he probably didn't torque the bolts good when he replaced the engine the engine sounds quite.

    • Guest - darrell

      got stuck in 98 tahoe now it sounds like chain rattling on front drivers side dont know if its transfer case

    • Guest - darrell

      my 98 tahoe makeing chain rattling sound from front drivers side was stuck in mud and snow prior to the noise

    • Guest - john rogers

      My motor is make a loud nock noise y

    • Guest - James

      I have a tick in the engine of my 2006 5.3 chevy silverado that comes every now in then. I can shut it off for a while and it will ho away. Any ideas?

    • Guest - shortys transmission and auto repair shop

      In reply to: Guest - James

      Replace the oil filter and oil some filters have a spring loaded check ball that sticks if all good iv changed a lot of oil pumps and pick up tube best thing to do is take oil sensor out and install a oil pressure gauge check for low oil pressure at the time the motor is making the ticking noise.

    • Guest - Gerardo

      I accelarated my trailblazer to much a noise out of the engine started hearing and i got a messege stop engine but i kept going until the motor shut off wen i decrease the speed

    • Guest - Kmom

      My truck makes a thudding noise but only when ur driving and push down gas to accelerate it doesn't do it idling

    • Guest - eric mallon

      I got a 1998 tahoe its making a lil ticking noise after I got unstuck on some ice

    • Guest - Joe

      In reply to: Guest - eric mallon

      If you over revved the engine when stuck on the ice, you could have damaged the engine. May be a ticking valve lifter.

    • Guest - frank

      In reply to: Guest - Joe

      My inpala suck

    • Guest - Ti

      I just bought a 2000 Chevrolet blazer. Haven't had it for a week and noticed that the longer i drive it, i start to feel a pull. When i took it to my mechanic, he said it was the main piston heating up and causing the oil pressure to drop. Which could freeze the engine. I took it back to the dealer and they tried to say nothing was wrong with the car but they would look at it. I am not sure what to do. Should i keep it if the dealership can fix it or will it be a problem later down the road

    • Guest - Bob l.

      In reply to: Guest - Ti

      Not sure what an oil pressure problem has to do with the truck pulling. There is no such thing as a main piston. Low oil pressure could be a main bearing. Yes, this could cause the engine to lock up. I would get any oil pressure problem fixed ASAP !

    • Guest - John

      The " noise seems to be be coming from passenger side underneath the power steering pump

    • Guest - John

      2001 Ford Taurus with a loud mechanical noise that is constant when engine is idling in park , reverse , drive . Would like an opinion on what could be causing this noise please .

    • Guest - DJ

      06 Ford F 150 started ticking about a week ago. Dont hear it in idle only when giving it gas and whole truck jerks especially going up hill. any ideas?

    • Guest - ken

      My 99 f-150 is making knocking noise. I do not hear it when in idle or neutral or when giving it gas

    • Guest - Stephanie J

      I have a 2004 Pontiac Grand Prix that just started Knocking and ticking yesterday. When i started the car it made a noise like something was stuck in it and now makes the other noises. The ticking is consistent but he knocking is not. Was told it is either the rods or it could be a torque bolt. Any idea?

    • Guest - Stan

      In reply to: Guest - Stephanie J

      If the motor is knocking and ticking, you have big problems. Check your oil level and see if it is contaminated with coolant. It really does not matter exactly what is making the noise, the engine has to come apart and get repaired.

    • Guest - isaac

      My 04 i35 just got out of the shop . they changed the rod bearings but its been 2 weeks and its still knocking and it started shaking? Any ideas

    • Guest - jennifer

      i just bought a 01 v6 mustang not even 5 days ago. everything was going sooooo smooth.. then when i came up on a highway toll, the car seemed to die. I put it in park and re started it.. then all of a sudden a knock/ tick started.. it is semi loud but due to my loud exhaust its kinda hard to hear.. if i go 50 mph + it seems to go away. well as i was trying to drive it to get looked at i had to wait for a train.. It died randomly again.. when i turned it back on it seemed to knock/tick more. some people keep saying it the 02 sensor, some say its the lifters that are bad.. any ideas?

    • Guest - ian n

      In reply to: Guest - jennifer

      Was it just the knock/tick or was there a fair amount of engine vibration that could be felt a lot in the steering wheel and shift knob? Because I have had a problem with the harmonic balancer wheel assembly for my 2001 v6 mustang before too, but it was due to the balancer becoming un aligned and it made a lot of vibration and rattling. Having already successfully fixed that problem by replacing the Hbalancer assembly and installing the new factory part, it has been running fine...great even. So last week I also fixed the AC by charging the frion and eliminating any leakes. Well, so bringing us up to todays issue...heres what happened, I was dangerously low on gas as I pulled off the busy freeway and immediately said, "I gotta get gas." literally as soon as the words left my mouth, the car started idling funny and bogging down slightly and becomimg less responsive when I would try to manipulate the accelerator, so I figured, "oh, I must be running out of fuel like RIGHT NOW". So miraculously i was able to coast into the station and up next to a gas pump, where I preceeded to pump $10.00 worth of 89 octane into the gas tank of my green V6 Mustang coupe, well normally I would just put in the, bottom of the barrell, 87 octane, but I figured if it was that low on gas, then maybe I should give it a little treat, and start putting in better gas. I dont know what happened or if anything I did was the cause but now its making engine noises like Im hitting valves against pistons and possibly feels like maybe the motor mounts are somehow failing too. Definitely works better in certain gears compared to others but Im not sure if it has to do with the speed at which Im travelling or the actual gear itself. SOMEBODY HELP ME PLEEEAAASSE!!!!!
      Ian D Newsome (602)760-6334

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