Mechanics

Engine Noises

Step by step troubleshooting instructions on how to fix abnormal engine noises. This article pertains to all non electric vehicles.

Difficulty Scale: 4 of 10

Tools and Supplies Needed

  • Flashlight
  • Small mirror
  • Protective eyewear and gloves
  • Wrench and socket set
  • Hydraulic jack w/stands
Some engine noises are normal for example: some Chevy and Ford engines have short skirt pistons or all roller valve train, a minimal amount of engine ticking noise is normal. Fuel injectors also make a slight clicking noise when the engine is idling. These noises are normal and no repair is required, but if unexplained noises exist, the following steps are the most common causes.

Step 1 - Check the engine oil level, an engine depends on clean oil to lubricate the internal moving parts, if the oil level is low or dirty it can cause internal engine parts to malfunction. For example: a valve lifter is responsible for holding valve train clearance to a minimum, if the oil level is low or dirty it can cause the lifter to fail which will allow excess valve train clearance creating engine tapping or clicking noise. In extreme cases it can cause one of the many bearing surfaces to fail causing permanent engine damage. An engine making a slight noise, changing the engine oil and filter with the manufacturers recommended weight (viscosity) oil sometimes helps. Visit - Engine oil change

Step 2 - A squeaking noise could be generated by the engine accessories, accessory mounts, serpentine belt or drive pulleys. When an accessory, accessory bracket, belt or drive pulley fails it can make a rattling, squeaking or tapping noise. These sounds are centrally located near the front of the engine. With the engine off, check the tension of the belt/belts, it should be at medium tension a loose or worn belt can make a loud squealing or chirping noise, check the belt tensioner and the size of the belt to make sure the right belt is installed. To isolate the origin of the noise, remove the serpentine belt and start the engine. Visit - Serpentine belt removal

If the sounds disappears an accessory, accessory bracket, belt or pulley has failed. With a flashlight inspect the brackets and pulleys that connect the alternator, air conditioner compressor, power steering pump, and air pump if equipped. Look for signs of rust (reddish pounder), this indicates a broken or loose metal part rubbing together, which can generate squeaks and ticking noises. If the brackets look okay rotate each accessory pulley by hand and check for hard spots or a seized bearing.

Step 3 - If a tapping or ticking noise from the upper half of the engine remove the valve covers. Each valve utilizes a spring that returns it to its original position, closed. If a valve spring has broken or a cam lobe is worn down it will cause the engine to create a tapping or clicking sound due to the excess clearance. To test for this condition, remove the ignition coil connector, ignition system or fuel pump fuse to disable power to the ignition or fuel system. Have a helper crank the engine over while watching the rocker arms or cam lobes, making sure all valves are traveling the same amount. If one or more lobes are traveling less than the others the engine has a flattened cam lob and the camshaft needs to be replaced, or the hydraulic lifter/follower (where applicable) has collapsed and will need to be replaced. Also inspect the condition of the valve springs, using a flashlight and a small mirror to aid in the inspection to look for broken springs. If a broken valve spring is discovered replacement is required to correct the problem. When checking valve springs look at the height of the valve springs and retainers in the closed position, they should be exactly the same height. If one valve is higher or lower something is wrong with the cylinder head the valve or valve seat and needs to be repaired.


Replacing a Camshaft

Step 4 - If a heavier noise seems is being generated from the lower half of the engine, the problem can be more serious and disassembly maybe required. But, sometimes a lower engine noise could be generated due to excessive carbon, (carbon is a natural byproduct of the combustion process which builds up on top of the piston.) This knocking noise is created when carbon is compressed between the piston and the cylinder head. To repair this problem the cylinder head needs to be removed.

Step 5 - Some engines are manufactured with a timing belt. This belt is kept under tension by the belt tensioner. The belt tensioner is constructed with a bearing that can sometimes fail, creating a squeaking noise or chirping sound. Also, when this tensioner or timing belt starts to fail it can cause the timing belt to misalign. This condition will cause the timing belt to shred producing ticking/scraping noises inside the timing belt cover.

Step 6 - A flex plate is used in automatic transmission applications. Its used to connect power form the engine to the torque converter of the transmission. When a flex plate fails it usually cracks at the crankshaft mounting bolts. This will make little to no noise at idle, and make more noise depending on how much load the engine is under. The more throttle that is applied the louder the noise will become. To check for this condition remove the flywheel inspection plate or cover. Using a small flashlight and mirror, check for signs of rust dust near or around the bolts. Rust dust indicates a break or crack. Its these cracks flexing back and forth that generate the ticking noises. Replacing the flex-plate requires removing the transmission.

Step 7 - The IAC motor (idle air control) controls idle air to the engine. When an IAC motor fails it creates a loud humming sound when it fails.

Step 8 - Some engines are equipped with a cam angle sensor. This particular sensor is basically a distributor housing with a sensor and trigger plate mounted to the center shaft. If the sensor seizes due to lack of oil a high pitched squeaking noise will be produced. To check for this condition remove the serpentine belt and restart the engine. If the noise is still present suspect the sensor housing.


Helpful Information

Today's engines have been designed with more complexity and moving parts than ever before. Most of the time when you hear abnormal noises there is something going wrong. Excess engine noise is due to excessive clearance between two internal metal parts that should have little to no clearance. This clearance can be due to many things from a broken valve spring to a crankshaft bearing that has failed. The first step is to identify where the engine noise is being generated, with the engine running isolate where the noise is coming from in the engine, either the upper half, lower half, front half or rear half. (note: listen from above the engine or below the engine as this will help determine where to start looking for the cause of the noise.


Crankshaft Bearing

Best Practices

  • To avoid engine noises change your engine oil every 3,000 to 5,000 miles with normal motor oil, and 6,000 to 8,000 miles with synthetic oil.

AUTHOR


Written by
Co-Founder and CEO of 2CarPros.com
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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