What Can Cause an Engine Knock


A knocking noise coming from your vehicle is never a good thing-unless the neighbor’s cat has gotten caught in the belt. The sound is usually coming from the motor if you can hear it when you start the vehicle or when it is idling. If you hear it while driving, it is most likely caused by something other than the engine.


Noises from the engine

The motor is responsible for the majority of knocking noises in automobiles. Or some of the parts dangled from it. And they are almost always serious and should be dealt with immediately, if not sooner. Engine knock should be less of an issue in newer vehicles because air/fuel mixtures, injectors, and timing are all controlled by computers that feed information into the knock sensor. This resolves the issue. Unless the knock sensor is malfunctioning and causing the knock.


Engine oil is low

Engine knocking and engine damage can result from low engine oil. Low oil levels are typically caused by leakage, burning oil, or putting in too little during an oil change. When empty, a Hemi requires 7.5 liters of oil. The oil change crew only used 5 liters-twice. Examine your oil levels. Hopefully, raising the oil level to the recommended level will eliminate the knock. Unfortunately, by the time you hear the engine knocking due to low oil, the damage has most likely already begun. If the oil level remains low for an extended period of time, the next knocking you may hear is a broken rod attempting to pound a hole in the engine block. A knocking or tapping sound from the upper engine can also be caused by a lack of lubrication. This is frequently caused by valves or lifters not receiving enough oil.


Knock on Wood

Improper air/fuel mixtures cause detonation knock. Instead of a single uniform explosion, the fuel burns in individual pockets. If the mixing issue is not resolved, piston and cylinder wall damage can occur. Other possible causes of detonation knock include low octane gasoline. Using lower octane fuel can result in knocking. Fuel with a higher-octane rating resists premature detonation. This pre-ignition problem is easily solved by using higher octane fuel that matches the vehicle’s recommended level. Alternatively, you could purchase an octane booster. Deposits of carbon. Carbon buildup on valves, spark plugs, and even piston heads reduce cylinder volume, increases compression, and can result in premature detonation and knocks. Adding an injector cleaner or carbon cleaner to the fuel tank will usually solve the problem.

Inadequate spark plugs or a plug gap This is usually a quick and easy fix. Simply take out a couple of plugs and make sure they match the manufacturer’s recommendations. The recommended spark plug gap is also listed in your owner’s manual. You can check and adjust the gaps as needed if you have a spark plug gapping tool.


Timing Chain Is Loose

A faulty timing chain can produce knocking, clattering, or rattling sounds from the motor’s front end. A stretched chain, or a failed guide or tensioner, is frequently the culprit. The noise you’re hearing could be a loose chain banging on the cover. Timing chains regulate the timing and order in which valves open and close. Timing chains that are off by a few seconds can cause valve or piston damage because bad timing contributes to detonation knock. As soon as the problem is identified, timing chains should be repaired. The longer it goes unattended, the more damage it can do. If you’re not sure about doing it yourself, take it to a shop. It can be an expensive repair, but it pales in comparison to valve and piston replacements.


Valve Train Wear

When valve trains, which include rocker arms, lifters, and camshafts, become worn, they will make knocking or tapping noises. The noise usually comes from the engine’s top. Aside from the normal wear and tear of metal parts interacting with one another at high speeds and temperatures, driving with low oil levels will cause parts to wear out faster. Keeping the oil at the proper level and changing it regularly will help to reduce valve train wear.


Idle Knocking and Other Noises

Often, the best time to listen for engine knocking or other strange noises is immediately after starting the vehicle. There is no road noise, and no engine or exhaust noises. The engine is now cold, and the majority of the lubricant has returned to the oil pan. If you have a valve train problem, you will notice it during startup. Along with detonation issues and low oil issues. Any or all of those knocking and tapping noises should appear early on. If none of these are life-threatening, they will vanish quickly-usually within a minute-making turning off the radio and listening to the motor instructive. Along with engine knocking, you might hear knocking, scraping, grinding, howling, or other horror movie sounds coming from the front end of the engine. Where the alternator, air conditioner compressor, water pump, and belt tensioner are held together by loose bolts and rotate on worn-out bearings.

Any of these necessary pieces of equipment can produce knocking, scraping, grinding, howling, or screaming noises. If you think you hear something out of the ordinary during startup, open the hood and try to isolate the noise. Even if you have no intention of attempting to repair the problem yourself, giving the mechanic a hint as to where to start looking can be helpful.