About Engine Noises


There are a plethora of components that move around in today’s car engines and sometimes they create noises that you should pay attention to. To assist you, we’ve put together this brief guide to diagnosing common engine noises. Because they work on cars all day long for their living, trained mechanics have ears that are more tuned to sounds that emanate from engines than we common folk have. A good mechanic will usually be able to diagnose an engine noise quickly.

Hissing Noise

Have you ever heard your engine “hiss” while you’re operating the car, but specifically while you are idling it? It is not a nice noise. However, it is a warning sign that your vacuum line could be damaged, and result in your “Check Engine” light coming on. You may have to get lines reattached, or purchase a new vacuum line.

Valve Noise

Exhaust and intake valves are mushroom-shaped objects that move up and down in an engine for allowing fresh gas into and exhaust gases out of your combustion chambers. The valves themselves usually don’t make noises but the rocker arms and tappets (part of your “valve train”) do. When these rocker arm and tappet noises are loud, they make noise, and the mechanics at Sandovalbuickgmc.com say it usually means the valves just need adjustment. Technically, the noise is a sound that is half the speed of your engine’s pistons and flywheel. You can always hear a small noise in a running engine but if you hear loud clicking sounds, visit your local dealer and have them check it out.


Detonation is when an engine’s air/fuel gas mixture is ignited before it’s due to be. It’s a sound that you will hear when you’re driving, usually when going up a hill. Detonation sounds are like that of metallic rattling, they are quite noticeable. The really important thing to know is that if it happens for a long time, it can cause serious damage to your engine. Never ignore an engine that detonates for longer than five or ten seconds. Usually detonation is caused by simply running an engine on a low octane level. Vehicles with high compression levels need higher octane levels so if you think an engine is having detonation issues, try to increase the octane level of your fuel next time you fill up. That could be all it takes to fix a detonation problem.

Crankshaft Knock

The most annoying noise that an engine may have is a crankshaft knock–a sharp, rapping sound that gets particularly loud when an engine turns faster. If you hear a crankshaft knock, it usually means an engine is destined to fail. If you hear a loud knock coming from your engine, it’s probably a crankshaft knock and you’ll need to immediately bring it to a mechanic.

Piston Slap

An empty, dull, almost bell-like sound is almost always a piston slap. The condition is the result of a well-worn piston rocking back and forth within its cylinder. Piston slap only happens when an engine has tons of mileage on it. A continuous piston slap means the engine needs a repair; however, if you only notice the sound when the engine is cold, it is likely not serious. Unless you are a mechanic, you may not know what a piston slap is or means.

As we have mentioned, identifying engine noises can be difficult for the typical driver. If you feel an engine noise is not ordinary, it is a good idea to stop by your local car dealer for diagnosis.

Article Source: Sandoval Buick GMC


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