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Home / Symptoms / Lawn Mower Noise

Four common causes for a lawn mower sound from the vehicle and their related parts.

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Common Causes for Your Car Sounding Like a Lawn Mower

The lawn mower sound is typically due to a crack in the combustion system. A vehicle's combustion system features many components, such as cylinders, spark plugs, and exhaust, which are all susceptible to damage and lead to car sounds.

Watch out: If your car makes a lawnmower noise, you might be in for combustion issues, which can progress into engine misfires, bad fuel consumption, a loud noise, and in the worst cases, fire hazards. Plus, besides the risk of fire, the lawn mower sound means engine components are at risk of damage. Eventually, these components can break, causing the engine to stall, meaning the car can die on you unexpectedly.

The most common causes your vehicle makes a lawn mower sound

The most common causes for the lawn mower sound are:

A crack in the exhaust system: The car's exhaust system serves as a sort of "straw" that throws engine gases to the outside. When the exhaust cracks, it affects the flow of gases, leading to exhaust system leaks, which results in weird lawn mower sounds.
Faulty head gaskets: A car's head gasket is a sealing component inside the engine that prevents fluid and gases from the engine's cylinders from mixing up. However, when this sealing fails, it can allow leaks; the leak can lead to fluid building up on hot surfaces and produce gurgly lawn-mower-like noises when the vehicle is running.
Faulty spark plugs: Spark plugs are engine components that create a spark; the spark they create ignites the fuel in the combustion process and makes the car start. However, when spark plugs become faulty, like when they are malpositioned or overheating, they fail at "sparking" and produce noisy detonation, resembling a lawn mower sound.
Engine misfire: An engine misfire happens when there's an issue in the combustion process. Cylinders work with spark plugs and perform controlled explosions in the combustion process, but when a spark plug is faulty, a cylinder might do this explosion wrongfully; this is called a "misfire," and it sounds like a lawn mower.
Faulty wheel bearing: Wheel bearings are components that help support the car's weight and provide balance; they're found between the wheels and a large metal rod below the vehicle called an axle. However, a failed wheel bearing causes more rolling friction, generating a lawn mower sound.
Exhaust manifold leaks: The exhaust manifold is a component inside the engine that collects the resulting gas from cylinders and leads them outside through the exhaust pipe. However, if there's an exhaust system leak, the exhaust manifold changes the tone of the exhaust gases, producing a lawn mower noise.

Frequently Asked Questions

Do you notice white smoke coming from the tailpipe?

Blown head gaskets can make your car sound like a lawn mower. In this case, note that a few other symptoms come along. For example, you might notice white smoke from the tailpipe, bubbling in the radiator and coolant reservoir, coolant loss, white-ish oil, and engine overheating.
Is your engine misfiring?

Engine misfires can cause this issue. In such cases, it's common to notice chugging sounds, power loss, vibration, burning match-like smells, and excessive exhaust smoke. Also, the dashboard usually holds the check engine light on or flashing.
Are you noticing an odd sound coming from the exhaust?

Usually, if it's an exhaust leak, you'll notice a noise that changes with engine speed. Also, watch out for fuel economy since this leak impacts it negatively. In addition, it's common to have the engine light pinging on the dashboard. Finally, exhaust fume smells can also indicate exhaust leaks.
Do you hear chugging or banging noises?

A failing spark plug often causes this issue. In this case, the noise might even resemble chugging or banging. Usually, the symptoms that come along with this issue are fuel mileage loss, engine underperformance, lengthy starts, engine vibration, and rough idling.
Are the wheels feeling odd or making humming noises?

A faulty wheel bearing can also cause humming or squealing sounds. In addition, keep your eye open for ABS failures, steering wheel vibration, and looseness, for they are satellite symptoms.
Have you noticed any changes in the noises coming from the engine?

If this is the case, it's common to notice the noises changing as the engine cools down and again when it’s running at operating temp. You might also feel power loss, fuel economy loss, and exhaust fumes smell in the driver's compartment. Also, watch for your car's dashboard; the check engine light might be on for emissions-related failure. Finally, you might see missing bolts from the exhaust manifold or glowing red areas in dark engine compartments.

Typical fixes to address the cause(s)

These are typical processes and repair services that fix a check engine light issue

The most common cause: Combustion issues

The most common reason for a car making a lawnmower noise is an issue in the combustion system. Your vehicle’s combustion system depends on the engine’s movements and internal mechanical cycles between pistons, valves, etc. Over time, issues can happen to the engine’s components, like a faulty head gasket, a valve crack, or a seal malfunction, which results in combustion gases escaping. When the combustion gases escape and leak out, the vehicle can sound like a lawnmower.

Symptoms it causes: Apart from the lawnmower noise, you might notice engine misfires, emission test failures, smoke from the hood, engine overheating, bad fuel economy, stalling, etc.
High risk of priority: Any issue in the combustion system means that the engine is suffering stress and further damage. Eventually, internal engine components can fail, resulting in severe symptoms and even a vehicle breakdown.

How exactly do combustion issues?

Combustion issues can happen due to a failure in any of the internal engine components that take part in the combustion process. There are many seals, valves, pinions, and gaskets that move synchronized to ensure the engine can convert fuel into mechanical power so the vehicle drives properly. Sadly, a failure in any of these components can lead to fuel vapors and useful combustion gases escaping, affecting the engine’s performance.

Go safe: Ask for a mechanic to inspect your vehicle’s combustion system, including the engine, fuel tank, catalytic converter, spark plugs, etc., to investigate the lawnmower noise and see if it means further damage. Many shops do transparent vehicle inspections and lay out your options after investigating your vehicle’s conditions.

What’s a vehicle inspection? It’s “detective work” on your vehicle, checking its systems to find if anything is preventing the car from working as expected. In this case, mechanics examine different parts of your vehicle to track what’s causing the combustion system to cause lawnmower noises. They’ll also check the condition of components during their inspection, noting which are causing the problem and which got affected by it, recommending to replace them in order of priority.

Transparency example in a combustion-related service

A combustion system inspection is the most transparent process to understand why your vehicle is making lawnmower sounds. Let’s read an example of how this kind of inspection defines the service needed to fix a combustion-related issue in a vehicle.

In a scheduled service, a customer stated their car was making lawnmower noises; ‘looks like a lawnmower is working under the hood,’ in their own words. The technician opened the vehicle’s hood and inspected the engine’s internal components, fuel lines, and exhaust system for any issues.

After checking the engine in more detail, the expert found that the fuel injectors, which spray fuel into the engine chamber to start the combustion process, were clogged up in dirt.

A clogged fuel injector can’t keep up with the engine’s fuel demand, resulting in a bad air-fuel mixture, resulting in engine misfires, and bad fuel economy. Additionally, a clogged fuel injector can progressively damage the engine and quickly turn into something expensive.

The image below shows the technician’s first look at the clogged fuel injector.

Clogged fuel injector

In this case, the mechanic put the “Immediate Action” tag on the faulty fuel injector.

Similar Symptoms

Below are just a few examples of typical Symptoms and Fixes your car might be experiencing

Four common causes for a squealing noise from the vehicle and their related parts.

Common Causes for Your Car Sounding Like a Lawn Mower

The most common causes your vehicle makes a lawn mower sound

Frequently Asked Questions

Do you notice white smoke coming from the tailpipe?

Is your engine misfiring?

Are you noticing an odd sound coming from the exhaust?

Do you hear chugging or banging noises?

Are the wheels feeling odd or making humming noises?

Have you noticed any changes in the noises coming from the engine?

Typical fixes to address the cause(s)

The most common cause: Combustion issues

How exactly do combustion issues?

Transparency example in a combustion-related service

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