Diesel Engine Knocking Prevention & Solutions

Diesel Engine Knocking Prevention and Solutions
July 12, 2023

If you hear a strange sound coming from your vehicle’s engine, it’s trying to tell you something. When your vehicle starts making a knocking noise, it’s time to take action.

Engine knocking can indicate something is wrong with your fuel, ignition or vehicle’s mechanics. If you ignore the noise, your fuel efficiency will drop and your engine may be permanently damaged. Learn what to do when your vehicle starts making noise. 

What Is Engine Knocking?

Engine knocking is a sound that occurs when your vehicle’s cylinders don’t burn fuel evenly. Ideally, the mix of fuel and air in each cylinder will be balanced so that small pockets of fuel and air burn in small amounts. When the mix becomes unbalanced, multiple fuel and air pockets burn at once, producing a knocking noise. 

The knocking noise in the engine may start out quietly, becoming louder as you continue to drive — or on later trips if the issue isn’t treated. Left unresolved, engine knocking can cause damage to the pistons and cylinder walls of the engine. 


What Causes Engine Knocking?

There isn’t a single cause of engine knocking. The sound can occur when part of the engine is worn out or due to choices you’ve made about your vehicle — especially regarding fuel. Engine knocking can also be the result of ignition problems or mechanical concerns.

Fuel-Related Causes of Engine Knock

The type of fuel you choose for your vehicle matters. You don’t want to put regular fuel in a diesel engine, for example, or choose the wrong cetane rating for your engine. The following fuel issues can all contribute to engine knock:

  • Wrong cetane rating: Diesel fuel has a cetane rating from 45 to 55. It’s important to choose a cetane level that’s recommended for your engine to prevent knocking.
  • Contaminated fuel: Knocking can also be a sign of contaminated fuel. Dirt and debris can mix in with your vehicle’s fuel, leading to buildup in the cylinders. You can use fuel additives to clean the oil or bring your vehicle in for a tune-up to have the cylinders cleaned.
  • Improper fuel-to-air ratio: Too much air and not enough fuel in the cylinders means your engine needs multiple combustions to get going. Those multiple combustions will produce a knocking noise. 
  • Improper fuel additives: Using the wrong additives — like an additive meant for a gas engine in a diesel engine — or using more than the recommended amount can cause incomplete combustion, producing a knocking sound.

Ignition-Related Causes of Engine Knock

Fuel isn’t always the cause of engine knocking. Sometimes, an issue with your engine’s ignition is to blame. Incorrect ignition timing is a common cause of engine knock. Timing matters for your engine. If the air-fuel mixture ignites too soon, it will produce a loud noise. 

Another common problem is a loose timing chain. Repairing the chain will correct the problem and prevent additional damage to your vehicle’s engine.

Mechanical Causes of Engine Knocking

Occasionally, a mechanical issue with your vehicle’s engine leads to a knocking noise. Three common mechanical causes include:

  • Excessive carbon deposits: Carbon deposits can develop in the engine’s cylinders, fuel injectors and chamber walls, creating a buildup that leads to a knocking noise. Along with producing noise, carbon buildup can reduce fuel efficiency and may lead to overheating. 
  • Compression problems: Your vehicle may make a knocking sound when there’s an issue with the compression system. That could include leaky valves, damaged cylinders or worn-out piston rings. 
  • Worn-out parts: Old bearings, a damaged crankshaft or a stretched-out belt can all contribute to engine knock.
  • Overheating: Your vehicle can overheat if the oil or coolant is low, if there’s a problem with the cylinders or when the weather is hot. Overheating increases cylinder pressure, which leads to incomplete combustion. Along with a knocking noise, you’ll probably notice other signs of overheating, including a burning smell, smoke from the engine and the temperature gauge in the red zone.


Symptoms of Engine Knocking

There are a few ways to know if your engine is knocking. Pay attention when you notice:

  • Audible knocking sounds: One of the first signs of engine knocking is the sound. At first, you may just hear a few soft knocks. The noise is likely to become louder as you continue to drive.
  • Vibrations or rough engine performance: If you don’t take action at the first sign of engine knocking, you may notice that your vehicle shakes or handles less smoothly on the road.
  • Loss of power or reduced fuel efficiency: You may also notice that you need to refuel your vehicle more often. Damage to the cylinders can affect fuel efficiency and overall performance.


Risks and Consequences of Engine Knocking

Take engine knocking seriously, even if it’s not loud initially. If you ignore that knocking noise, your engine components can become permanently damaged and need replacement. Ignoring engine knocking can also reduce the life span of your motor and increase the cost of repairs and maintenance.


Engine Knocking Prevention and Solutions

Fixing or preventing engine knock can be quick and simple depending on the cause. Often, using the right fuel can be the best way to prevent engine knock. Pick a fuel with the appropriate cetane rating. It should be free from debris and impurities. 

A cetane booster, such as Diesel Extreme or Everyday Diesel Treatment, can help protect your engine and improve its performance.

Beyond improving your fuel, a few other practices can help prevent or reduce engine knocking:

  • Inspect and maintain your fuel system: Schedule regular fuel system inspections and get the filters, injectors and pumps serviced as needed. Replacing faulty parts or cleaning clogged parts is key to making sure fuel is delivered and injected into the engine properly.
  • Schedule injection timing inspections: A qualified mechanic can inspect your vehicle’s injection timing and make any needed adjustments to the fuel-air ratio.
  • Perform regular maintenance and cleaning: Have your engine cleaned periodically to remove carbon deposits from the injectors, piston crown and combustion chamber. You can either use a fuel injector cleaner or schedule a professional cleaning.


Reduce Engine Knock With Hot Shot’s Secrets

At Hot Shot’s Secret, we offer a range of fuel additives to keep your engine running smoothly and help prevent engine knock. Browse our selection today and contact us with any questions or for more product information.