New Hub Auto

Facebook Assistive-listening-systems Yelp Instagram
Book Appointment

Why is there a knocking noise from the engine?

Decoding the Knock: What’s That Engine Noise All About?

That tell-tale knocking sound emanating from under the hood can be a car owner’s worst nightmare. It’s often a sign that something’s not quite right within your engine’s intricate workings. At Newhub Auto Repair, we understand the anxiety a strange engine noise can cause. That’s why we’ve put together this guide to help you understand the potential causes of that knocking sound and what it might mean for your vehicle.

The Anatomy of an Engine Knock: Understanding the Sounds

Before diving into the potential culprits, it’s important to understand that “knocking” can encompass a range of sounds. Some knocks are subtle and almost imperceptible, while others are loud and pronounced. The severity and frequency of the knock can often provide clues to its origin. Pay attention to when you hear the noise – is it constant, only during acceleration, or when the engine is cold? These details are crucial for diagnosis.

Common Culprits Behind Engine Knocking

1. Detonation (or “Knock”): The Fuel’s Fault

One of the most common causes of engine knocking is detonation, often referred to simply as “knock.” This occurs when the air-fuel mixture in your engine’s cylinders ignites prematurely, resulting in an uncontrolled explosion. This explosion collides with the piston as it’s still moving upwards, creating a knocking sound. Factors contributing to detonation include:

  • Using Low-Octane Fuel: Your engine may require premium fuel to prevent premature ignition. Check your owner’s manual for the recommended octane rating.
  • Overheating: High engine temperatures can increase the likelihood of detonation.
  • Carbon Buildup: Deposits inside the combustion chamber can create hot spots that trigger early ignition.
  • Faulty Spark Plugs: Old or damaged spark plugs can misfire, leading to incomplete combustion and detonation.

2. Rod Knock: A Serious Internal Issue

Rod knock is a much more serious problem and indicates significant wear or damage to the connecting rod bearings. These bearings sit between the connecting rods and the crankshaft, allowing them to rotate smoothly. When these bearings wear down, excessive play develops, causing the connecting rod to slam against the crankshaft, producing a distinct, rhythmic knocking sound. Rod knock typically gets louder as the engine’s RPMs increase.

3. Piston Slap: A Different Kind of Knock

Piston slap occurs when a piston moves excessively within the cylinder bore. This can be caused by worn piston rings, a worn cylinder wall, or improper piston-to-cylinder clearance. The sound is often described as a slapping or rattling noise, and it’s most noticeable when the engine is cold. As the engine warms up and the parts expand, the noise may diminish.

4. Valve Train Issues: Ticking and Tapping Can Sound Like Knocking

Problems within the valve train, such as worn or loose rocker arms, lifters, or pushrods, can also produce noises that can be mistaken for engine knock. These noises are often more of a ticking or tapping sound than a deep knocking. However, if left unaddressed, these issues can lead to more significant engine damage.

5. Low Oil Pressure: A Silent Killer

Low oil pressure can exacerbate many of the issues mentioned above. Without sufficient lubrication, moving engine parts experience increased friction and wear, leading to knocking sounds. Low oil pressure can be caused by:

  • Low Oil Level: The simplest and most common cause. Always check your oil level regularly.
  • Worn Oil Pump: The oil pump is responsible for circulating oil throughout the engine. A worn pump may not be able to maintain adequate pressure.
  • Clogged Oil Filter: A clogged filter restricts oil flow, reducing pressure.
  • Oil Leaks: Leaks can deplete the oil supply and reduce pressure.

What to Do When You Hear an Engine Knock

If you hear a knocking noise from your engine, it’s essential to take action promptly. Ignoring the problem can lead to more extensive and expensive repairs down the road. Here’s what we recommend:

  • Note the Details: Pay attention to when you hear the noise, how loud it is, and any other symptoms your car is exhibiting.
  • Check Your Oil Level: Ensure your engine has adequate oil.
  • Avoid Strenuous Driving: Reduce the load on your engine to minimize potential damage.
  • Schedule an Inspection: Bring your vehicle to Newhub Auto Repair for a professional diagnosis. Our experienced technicians can pinpoint the source of the noise and recommend the appropriate repairs.

Newhub: Your Partner in Engine Health

At Newhub Auto Repair, we’re committed to providing reliable and trustworthy auto repair services. Engine knocking is a serious issue that requires expert attention. Don’t wait until the problem gets worse – schedule an appointment with us today, and let us help you get your engine running smoothly and quietly again. We offer comprehensive engine diagnostics and repair services to keep your vehicle performing at its best.

Disclaimer: This blog post is for informational purposes only and should not be considered a substitute for professional automotive advice. If you suspect your engine is knocking, consult a qualified mechanic for diagnosis and repair.