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 - 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 - 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 - 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 - 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 - 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 - 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 - Timothy Milhomme

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