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

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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 (190)

    • 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 - 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 - 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

    • Guest -

      Right inside cam shaft...or were I insert oil there is a ticking sound on idle...tick..tick...tick. What could it be?

    • Guest - Bob

      In reply to: Guest -

      This i a tick noise from the upper engine. Possibly a rocker arm or push rod.

    • Guest - Jarrett

      I have a 91 s10. The vehicle idles fine when in park. When I go to put it in gear it idles rough until you touch the accelerator to start moving. It does this every time I stop even at normal operating temperature. When the vehicle idles rough it will also loose oil pressure and will bottom out and almost shut off. The check oil level light will come on but the check engine light has never came on. The oil level in vehicle is fine. Just changed about 200 miles ago. The mileage is around 250xxx. What is causing this?

    • Guest -

      i have a 2006 grand prix i put to much oil in my var drove it about 10 miles then drain it out 3daya later it started knockin no smoke tho what is the knockin noise and how do i fix it

    • Guest - Tom

      I have a 98 Chevy z71 with 5.7 ltr when I accelerate real fast or go up a hill on interstate pops through throttle body and exhaust any ideas. Ty

    • Guest - Hank

      In reply to: Guest - Tom

      A pop noise is usually an engine backfire or misfire caused by an ignition problem. It could also be a bad camshaft.

    • Guest - joshua

      i got a ticking noise coming from behind my motor and transmission it a 94 s10 5speed i replaced spark plugs and so much more to much to list but its kinda funny i think its a flywheel tick cuz it only happens when i step on the gas fast if i just slowly push it down it dont make a sound and at low rpms it makes the ticking sound and then when i drive down the road it only makes the sound when i step on it hard if i take off like a 90 year old make it dont make the sound let me know what u guys think thanks!!!

    • Guest - rick wilks

      I just bought a chevy ss trailblazer 2008 and it started to smell like gas was coming in from the vents in the chevy and it was sputtering and almost stalled last night. I took it to the dealer today and told them to check it out, they called me a couple hours later and said it didn't smell of gas and no sputtering. I went up and picked it up and when I left all the lights were coming on and said it was overheating and there was 2 engine lights on and then when I turned around and basically crawled in, there was a huge puddle of milk shake lookink liquid pouring out and where you fill it up with oil was smoking. and now I am smoking from being so pissed off. Of course no mechanics were there so I have to back tomorrow am. Any comment or explanation would be great. Thank you for your time

    • Guest - Jonathan Jones

      I just came back from a trip out of town and I started hearing a knocking sound in my engine. I pulled over and put some more oil into my vehicle. The knocking became less but was still there. Once I made it home I parked it and I have not driven it since. I have however cranked it and the light knocking noise is still there. Can anyway help me better understand this. I am going to take it to a professional tomorrow. But my main question is whether the knocking noise automatically means a engine that needs replaced. Im sure it could be many things possibly causing the knock. I just wanted to know if there is a chance it could NOT be "WORSE CASE SCENARIO ENGINE BAD". Hope that makes sense. Obviously something is wrong and needs replacing or fixed. I'm just hoping there is a chance it doesn't automatically mean I have to replace my engine. Thanks for any feedback.

    • Guest - Cliff

      I got a 95 silverado 5 spd. Runs great. Has a buzzing noise in floor board like at tranny or bellhousing. And itll stop when i pull out slow then goes back and stays buzzing

    • Guest - Wolfie

      I Have A Chrysler 300 Hemi It Was Running Fine Until I Passed Alot Of Water It Was Passing The Tire And Then The Car Just Stopped I Turned It On And It Made A Really Loud Knocking Noise I Checked The Oil And It Disnt Have Any But I Had Just Changed The Oil It SmoKes Alot Out Of The Exhoust Now And The Knocking Noise Is Still Really Louds Whats Wrong Whit It ?

    • Guest - Leonie

      Hi my holden VX was driving fine no noises no sigh a of anything was wrong, I accelerated from being stopped at a roundabout and next thing u know I heard a loud clunk noise and everything went stiff like the break and steering and turned off so I tried to start it again and it was making a weird noise but not making any attempt to turn over. My partner thinks he can fix everything but dosnt always have the best outcome so I need another opinion if u can plz.

    • Guest - Jerry

      I have a 1995 chevy tahoe. Started tuning rough no check engine like and underneath the car more so by the transmission I hear a clunking noise. I have no idea what it could be any ideas?

    • Guest - kyle

      I have a 90 Chevy 1500 and there is a knocking noise and does get louder when I accelerate. Wondering what I need to do to get it fixed. I have great oil pressure and do have oil in the truck. Only has 182000 miles on it. Am I ok to keep driving it?

    • Guest - angela

      I have a 2001 Chevy venture it makes a loud ticking noise con constantly. It does it all the time.its a lot worse when I ecellerate up a hill.

    • Guest - Guest

      I have a 2001 Chevy venture it has a rel loud ticking noise especially when I ecellerateup a hill

    • Guest - Alex

      I have a 2007 Ford Explorer Sport Trac. Recently it has been making a noise coming from the front of the drivers side. It makes a noise sort of like a loose chain and it only happens when I go over bumps even the smallest bumps on the roads. Any idea what it can be and how to fix it?

    • Guest - renni

      I have a 1999 dodge durango and its making a loud knocking sound when I crank it up..

    • Guest - justine

      My saturn sl1 2001 has a sound when I start the car as if it is over heating but it isnt. When ever I push the clutch in to shift gears the sound gets louder.all the way till I get to 5 th gear then it stops or sound really light. If I take my foot off tge gas my car feels like its pulling faster and fast but yet my cars at the same speed as if it's on cruise control butvisnt. I would like to know whats going on im tired of mechanic saying they know what it is and fix it and then something else is messed up

    • Guest - Ray Alestock

      What are the main bearing specs for a 1995 Chevrolet Suburban 350 engine, 2 wheel drive? Thank You! Vhcvq

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