Read descriptions and causes of some common engine noises. Knocks, ticking, rattling and more.

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 - Elizabeth Norton

    I have an 89 Ford Taurus wagon and I noticed a "ticking" noise coming from the fuse box under the steering column. Later in the day the battery was dead. I charged up battery and then noticed a "ticking" noise coming from the inside panel area in the cargo area in the back on the Drivers side. After a while I heard my car doors lock. The next day my battery was dead again.I had the battery checked out and it is good. The car will drive fine. I unhooked the battery cables for now. If the battery goes dead and it locks the doors I can't get in the car with the key. I had to use a slim jim to open a door. Now I keep a board under the hood when it is parked at home to create a little area so the hood won't latch so I can get to the battery if it goes dead. I have had about everything replaced on this little nightmare and it looks like a new car. I want to know what this problem is so I can get it repaired and then sell it. Any ideas? Thank you.

  • Guest - Ann Jones

    In my 2004 Avalanche i hear a tapping noise in first gear and then slightly worse in second gear. It completely disappears when im traveling down the road. Should i be concerned about this immediately?

  • Guest - 98 Sable Problems with Engine

    What is suggested to do to fix the following things wrong? Backfiring when starting and while accelerating, very low power accelerating, bad gas mileage, and timing off.

  • Guest - Jeffery Smith

    My 1996 GMC Jimmy truck has a knock when I tighten up the flywheel it stopped knocking but the other day I drove to the store and it stopped on me and would not crank anymore it was only clicking on the turnover not fully turning and I was trying to see the anyone know what that problem could be

  • Guest - Timothy Milhomme

    Driving home. Ticking noise from engine. It got louder then engine quit running. Has oil and coolant

  • Guest - bruce cole

    I have a 2006 pontiac G6 3.5L with 220 thousand miles. Now the motor allways ran real good I was driveing down the road and as i went around a curve the tappets started making a ticking noise.I replaced lifters ,oil pump and rod and main bearings . Still havent found problem

  • Guest - James mcmurrey

    I have a 2007 silverado. It has a intermittent loud knock. This knock comes and goes, and when it knocks I loose considerable power. My old 2 shows camshaft sensor bad. This knock sounds likable a collapsed lifter, but they are all good. What could it be? I also noticed when I checked the lifter the vacume hose that goes to the valve cover on driver side when I plug it off the noise is about one third of what it is when taken off the rocker cover.

  • Guest - Lloyd Smith

    2002 Chrysler M 300 ran hot died pull over to the side of the road let it cool couldn't get it to start finally did it had a real rough idle and it sounded like a scraping metal noise coming from the engine hasn't ran since is this a valve or something more in depth

  • Guest - David

    I have a 99 Ford ranger 3.0. I lost all oil pressure it lost power and the lifters are making noise. It doesn't smoke and I changed the oil there was no metal in the oil. I can't figure out what's wrong with it.

  • Guest - Jr

    In reply to: Guest - David

    You lost oil pressure, more then likely you toasted the rod bearings, Time for a rebuild.

  • Guest - Dillon

    My buddy was driving my 2006 Chevy equinox awd the other day when the car got hot and cut off they put water in it Jumpstart ed the car and drove it home it would not drive over 25mphalso there's a rattling noise coming from either the top or bottom in front of motor the car will run and stay running with no problems except the rattling noise sound like a chain being pulled down set of metal stairs

  • Guest - Jr

    In reply to: Guest - Dillon

    equinox are notorious for trashing the timing chain, and /or timing chain guides. A bad guide will cause excessive play in the chain, and will slap around or rattle. Have it looked at asap, that is a interference motor. If the timing chain breaks or skips a tooth, it will throw the valves into the pistons, and trash the motor

  • Guest - Ben Jacobs

    MY 440 mopar runs incredible at idle to 1500 rpm, but around 2000 rpm, the engine becomes overcome with loud rattling, noise, thousands of "rocks gone wild" come from the engine or transmission. It sounds like the motor is falling apart. We just rebuilt the top end in hopes of repairing a cam or valvetrain noise....but it only got louder I hear the automatic could do this, or the converter. I hope we don't have bearings somewhere causing this high rpm rattle that is terrifying.

  • Guest - Shenetta

    My 93 cavalier goes dead at take off now it won't start oil light has been coming on has oil in it before it had a knocking in it and now won't start

  • Guest - Tom

    In reply to: Guest - Shenetta

    The oil light does not mean oil level, it means no oil pressure. If it has been on for a while, then you have damaged your engine.

  • Guest - Taylor

    I have a 95 Ford F-150 on way to work I had a popping sound come from front of the engine slight sparks. I went to easy off road but still had power no drop in oil pressure or temperature change. I decide to continue slowly to get out of a high traffic area if possible. I made it no problems about 3-4 miles to the exit. Still no change just the knocking. I went back after work started right up but still knocks. I didn't drive. I'm wondering what may be the issue and if I should drive to the mechanic or just have it towed.

  • Guest - Schwery

    I have a 1994 Suzuki Sidekick 4x4 and hear a clicking sound somewhere in the left front only when driving for a while and the sound increase as I go faster, and decreases when going slower. This ocurrs even when driving straight and not necessarily when turning. What is causing this?

  • Guest - Larry

    In reply to: Guest - Schwery

    It is possible you have a bad front bearing, u joint, CV joint. Try it in 4 wheel drive to see if it goes away or gets louder.

  • Guest - Becca

    I have a 2009 Saab 97x. Was driving perfect no noise. Then it sounded as if something feel off under hood . And started to knock immediately and bogging out . Checked coil packs. Could it be spark knocking? Or is this serious?

  • Guest - Derek (MOBILE MECHANIC)

    i would like to ADD a cause i found in my repair. 2001 olds alero 3.4L engine knock. it was guessed the lifers had colapsed. during dissasembly and reasebly it was found. that when they replaced the intake manifold gasket, they didn't follow torque specs for the ROCKER ARM BOLTS. and one of the rocker arm was pivoting in it's spot, the wear was quite obvios where the knock was from

  • 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 - Jr

    In reply to: Guest - Celina Castellano

    White smoke from the exhaust is burning coolant, and the knock, is most likely a rod knock, burning oil is bad rings. Unfortunately, all combined.. the motor is toast, will need a complete rebuild, or replaced.

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