Lawn Mower Smoking And Leaking Oil From Exhaust [Fixed]

Lawn Mower Smoking and Leaking Oil from Exhaust

Lawnmowers are full of surprises, and their maintenance is not an easy task. Because you have to deal with lawn mower smoking and leaking oil from exhaust often and some other major and minor issues.

If you are seeing oil coming out of your mower’s exhaust and are worried about it, don’t be! It might be due to some mistake or mishandling by you. Maybe there is an oil spillage from the cocked or tilted lawnmower, or by inlaying excessive oil, maybe the lawnmower has an imbalance carburetor, a clogged air filter, or due to deteriorated engine. Most of these issues aren’t too challenging to fix, but finding the correct cause can be tricky yet helpful.

Leaking Oil

When your lawnmower is leaking or smoking, What causes smoke to come out of the exhaust? it’s important to find the cause so you can fix this problem. We’re here with solutions for fixing leaky oiled engines and preventing future problems with long-lasting fixes!

Also Read: 5 Best Oil For Lawn Mower

Lawn Mower Smoking And Leaking Oil From Exhaust

One of the major reasons for lawn mower smoking and leaking oil from the exhaust is Oil or Coolant leakage. Smoke from the exhaust is an indication of the attention-seeking engine problem. Smoke from the exhaust has different colors depending upon the various reasons and causes; it might be black, white, or grey smoke.

Let’s have a brief look at the smoke color along with its reasons, which helps you to diagnose the impact according to the intensity.

1. Black Smoke – Lawn Mower Smoking and Leaking Oil from Exhaust

Black smoke from the exhaust pipe is not an indication if it disappears when you come to a stop. But, continuous blackening of your vehicle’s Motorcraft should be concerning for safety reasons and may indicate roughhousing with other cars or trucks near yours as well!

Black Smoke

Reasons and Solutions to Avoid Lawn Mower Smoking and Leaking Oil from Exhaust

The black smoke has the following reasons:

1.1. Dirty Air filter

The air filter is a crucial component in improving the quality of your engine’s ventilation and ensuring that you can breathe easier while driving.

Dirty Air Filter


A dirty air filter can cause:

  • Harmful emissions.
  • The decrease in gas mileage.
  • The engine suffers a low air to fuel ratio.
  • Polluted spark plugs.
  • The engine becomes noisy and causes a fuel smell.

Ways to Avoid Smoke and Overcome the Impact:

The engine of your lawn mower can wear out, and if you’re noticing that it’s smoking or leaking oil from the exhaust then follow these steps to avoid a major problem in the future;

  • First, notice the intensity of the smoke.
  • Examine the air filter under sufficient light.
  • Make sure to clean the air filter as mentioned schedule in the user manual.
  • If cleaning is not suitable, then try to replace the air filter when you attempt oil changing.
  • Try to clean and maintain the air filter to keep your lawnmower healthy and efficient.
New Air Filter

Examine, clean, maintain, and replace the filter with time to prevent its impact on the engine. Stay calm! We are providing you with the products you might need. Select the product of your choice and need, make purchases just by clicking the products mentioned in the table to fix smoking and leaking oil from exhaust;

Lawn mower spark plug
Original Equipment Manufacturer (OEM) part
Compatible Brands: Craftsman, Tecumseh, Mtd, Sears, Troybilt
Air Filter
• Kawasaki OEM Air Filter
• Compatible with Cub Cadet, Toro, John Deere, Gravely, BobCat, Husqvarna, Exmark, Stens, Ariens riding / push lawn mower
• protect the filter from the dusty environment 
• extend working life.
Nylon Bristel Brush Set
Made of brass, stainless steel, and nylon
Strong and Durable
Rust Resistant
Suitable for cleaning and removing Dust, Rust, and loose paint

1.2. Poor Fuel Regulator

The fuel pressure regulator is to control the fuel pressure in the engine. So that the fuel system can perform properly according to its particular pressure range.

Poor fuel regulator


If the regulator stops working correctly, then the pressure will fluctuate, and it goes out of the range. It may have the following causes:

  • It can make it difficult for the engine to start because of low pressure.
  • High pressure can result in over-fueling, which makes the engine run rough and deliver low fuel mileage.
  • Effects fuel efficiency.

Ways to Avoid Smoke and Overcome the Impact:

To avoid all the above consequences, Follow the stepwise guide to clean, replace, and install the fuel pressure regulator the following way; if you don’t have a new regulator, you can order one from the link below!

Steps to Remove Fuel Pressure Regulator:

  1. Disengage the negative battery cord.
  2. Release the fuel system pressure.
  3. Eliminate the upper intake manifold adjustment.
  4. Disengage the vacuum channel from the pressure regulator.
  5. Remove the regulator retaining screw and remove the retainer bracket.

Use a clean cloth to catch fuel spillage, and carefully pull the regulator from the fuel bar. Twist the regulator slightly to make removal easy. You can buy a new one to replace the damaged part if needed;

Fuel Pressure Regulator Kit
Made of Aluminum Alloy
it regulates the fuel pressure against the air pressure
maintain the perfect ratio between fuel and boost
The fuel regulator pressure gauge range is 0-100psi

Steps to Install The Fuel Pressure Regulator:

  1. Make sure to clean all the parts. Avoid using compressed air to test or clean a fuel pressure regulator. Clean the fuel pressure regulator accordingly.
  2. If you found an infected pressure regulator, make sure to replace it.
  3. Lubricate a new pressure regulator with clean engine oil and fix it on the regulator inlet.
  4. Fix the fuel return pipe to the regulator.
  5. Install a new deposit and bracket into the fuel bar and install the pressure regulator to the fuel rail.
  6. Connect the vacuum line to the pressure regulator and install the retainer screw.
  7. Inspect and verify that the retainer and bracket are engaged in the slots properly. Grasp and pull on the regulator to ensure that it is well seated.
  8. Install the upper intake manifold.
  9. Join the negative battery cord.
  10. Inspect properly for oil leaking by starting and stopping the engine several times.

1.3. Unrepaired Fuel Injectors

Fuel injectors are small electro-mechanical devices used to spray a mist of gasoline into the mower’s intake manifold, which is right in front of the intake valve.

Clogged Fuel Injector

The gas can be drawn into the combustion chamber and mixed with oxygen to optimize the efficiency of the combustion event. Fuel injectors become clogged due to hydrocarbons present in the fuel. The water in the fuel can cause internal components to rust. Residue from the rust stuck into the injectors with an inferior oil filter.

Faulty windings and damaged springs can prevent the valve and injectors from properly opening and cause serious oil leaks.


Clogged or unrepaired fuel injectors can be the cause of bigger trouble. And can generate further issues like:

  • Seriously affect the efficiency and performance of the mower.
  • Inconsistencies in RPM.
  • It leads to continual oil leakage from the exhaust.

Ways to Avoid Smoke and Overcome the Impact:

To prevent lawn mower smoking and leaking oil from the exhaust, and inconsistent inefficiency of the lawnmower, these provided steps will help you out if you are facing the same issue with your machine;

  • Adding fuel injector cleaners and additives to the fuel helps in unclogging the clogged fuel injectors.
  • The filter basket must be removed, cleaned, and replaced for proper unclogging of fuel injectors.
  • The best way to unclog fuel injectors to avoid smoking and oil leakage is the ultrasonic way of cleaning injectors. You can replace old parts with new ones and test each injector for fuel flow comparison.

To unclog the fuel injector and to keep your lawnmower running, order Fuel Injector Cleaner now!

Fuel Injector Cleaner
Cleans restores, protects the entire fuel system
Restores power, acceleration, and lost fuel economy
Reduces, engine surge, hesitation, and spark plus fouling
Improves cold start performance, and fuel stability for up to one year
Oil Filter
Genuine Briggs & Stratton Oil Filter
Higher capacity Oil Filter
Provides maximum protection
Designed to meet the Higher operating temperatures

2. White Smoke – Lawn Mower Smoking and Leaking Oil from Exhaust

White smoke often exhausts when the engine burns the leaked coolant in the combustion chamber. It’s normal to deal with white smoke during every first-morning start-up.

White Smoke

Reasons and Solutions to Avoid Lawn Mower Smoking and Leaking Oil from Exhaust

It has the subsequent reasons:

2.1. Damaged Head Gasket

A head gasket is a combination of metal and graphite material, and it sits between the engine block and cylinder head in the engine. Its purpose is to avoid leakage of coolant or engine oil into the cylinders and to seal the cylinders to ensure maximum compression.

Damaged Head Gasket

The leaked burnt coolant can damage the engine. The overheated engine can be the reason for its damage. Mixing of water, oil, and engine additives can cause severe damage to the head gasket.


Once a head gasket has failed it can lead to other engine issues that can harm the unit in different ways;

  • Engine overheating.
  • Reduce cylinder compression.
  • The engine becomes rough.
  • Smoke from the exhaust.
  • It can cause severe coolant or oil leakage.

How to Avoid White Smoke and Leaking Oil:

Gasket repair is much more expensive and costly than making a replacement. You can prevent smoke and prevent oil leakage due to gasket with the simple precautions and steps;

  • Head gasket failure is the result of engine overheating, make sure that your engine is in good condition, and its cooling system is working correctly.
  • Avoid overfilling the coolant from a particular level. Make sure to check the radiator efficiency to avoid overheating.
  • Make sure to inspect belts and hoses properly, and replacing them before failure can prevent head gasket failure.
  • Perform regular maintenance of the engine and all connected parts.
Engine Gasket
• Genuine Husqvarna Engine Gasket Kit
• Compatible with Husqvarna, Poulan, and Craftsman
Kawasaki Head Gasket
Package Dimensions: 8 x 5 x 0.1 inches
Item Weight:
0.81 ounces
Kohler Head Gasket
Package Dimensions: 5 x 5 x 5 inches
Item Weight: 0.01 ounces
Manufacturer: Kohler
Briggs and Stratton Head Gasket
Package Dimensions: 0.1 x 8 x 9.75 inches
Item Weight: 0.8 ounces
Manufacturer: Briggs & Stratton
Antifreeze Engine Coolant
• Compatible with all models
• Contain Alugard Plus to provide maximum protection
• Lubricates gaskets and seals
• Protect against cold weather freeze-ups and hot weather boil-overs

2.2. Blown Cylinder Head

A cylinder head is located on the top of the engine block. It works as housing for components including; the intake and exhaust valves, springs and lifters, and the combustion chamber.

The cylinder head allows the air and fuel to flow inside the cylinder and at the same time, it allows the exhaust gases to flow out of it, which results in the lawn mower smoking and leaking oil from the exhaust.

Blown Cylinder Head

The cylinder head seals by the head gasket, and it avoids the mixing of water and oil, and it also prevents the excretion of oil and water from the chamber.

Engine overheating is the leading cause of a blown cylinder head, and it further causes oil to leak from the exhaust.


A cracked, damaged, or blown cylinder head can allow coolant leakage, which directly affects the engine cooling efficiency and can harm the engine in several ways;

  • It affects the engine efficiency.
  • Coolant leakage.
  • Oil leakage in the combustion chamber.
  • It leads to loss of power and performance of the mower.
Aluminum Cylinder Head
Made of good quality aluminum material
strong compatibility and is suitable for most generators and gasoline engines
good corrosion resistance
stable structure, excellent performance, and long service life

Ways to Avoid Smoke and Overcome the Impact:

If you are experiencing issues with the cylinder head, then we are providing you with the methods which are unfortunately quite expensive and also challenging to handle. It includes entirely repairing or replacement, without any other option;

  • Pinning technique. It involves pins to repair the damaged aluminum cylinder head. It is cheap and affordable.
  • Another way to repair cylinder heads is hot welding or furnace welding. It involves skills, practice, and a lot of heat for welding.
  • Another alternative for repairing damaged or blown cylinder head is powder welding or flame spray welding. It requires less heat for repairing the head strongly. Flame-spray welding requires a specific oxyacetylene flare with a trigger-operated tank that supplies nickel alloy powder into the flame. The powder melts and fuses in the flame on exposure to repair the damaged part.
  • Braze welding is another simple process to repair the damaged or blown cylinder head. It works fine for repairing cracks on the tops of cylinder heads as well as small cracks in exhaust ports.

2.3. Cracked Engine Block

An engine block contains the cylinders and other parts of an internal combustion engine along with a crankcase.

Cracked Engine Head

Advanced engine blocks have the crankcase, integrated with the cylinder block as a single component. Coolant passages and oil galleries are also part of the engine block.


A cracked engine block leads to the loss of structural integrity, that supports the cylinders, crankcase, and passageways.

A cracked engine block can lead to several problems that include issues from engine overheating to the decline of engine performance and efficiency.

It can affect the engine and its parts in several ways;

  • It causes frequent smoke from exhaust and also damages exhaust.
  • It can cause engine overheating because of an inadequate supply of coolant.
  • Generate milky oil by mixing oil and coolant due to hidden leakage in the engine passageways.
  • It directly affects and reduces engine performance and efficiency.

Ways to Avoid Smoke and Overcome the Impact:

If you have seen any of the symptoms or causes in your lawnmower, then we are providing you with all the possible solutions, that you can follow to avoid cracked engine blocks;

  • Re-welding technique to seal out all the parts of the engine again.
  • You can stitch the two sections together with the cold metal stitching technique.
  • You can use the cold welding technologies arising in the market to deal with engine cracks.
  • You can use the standard commercial sealers to seal the engine cracks.
Head Gasket Sealer
Repairs Blown Head And Intake Gasket Leaks
Seals Cracked Cylinder Heads And Blocks
Stops Heater Core And Radiator Leaks
Fixes Leaking Freeze And Core Plugs
Rubber Gasket
Rubber Grommet Assortment with 18 different sizes
Wide Range of Applications
rigid box to store, easy to open
Quicker and easier to install

3. Grey / Blue Smoke – Lawn Mower Smoking and Leaking Oil from Exhaust

Grey smoke is an indication of oil leaking and burning caused by it in the combustion chamber. This burning oil leads to further engine issues. It can cause damage to the catalytic converter as well as hydrocarbon emissions.

Reasons and Solutions to Avoid Lawn Mower Smoking and Leaking Oil from Exhaust

Grey smoke is the result of;

3.1. Malfunctioning Valve Stem Seal

The valve stem seal regulates the amount of oil applied to the valve stem interface, which is often used to grease the valve guide and the entire combustion chamber.

Seals, particularly made of high-strength rubber, fit over the top of the valve stem inside a small collar of the engine in your lawnmower.


When valve seals start to wear and fail, they produce some distinct and unusual symptoms;

  • Cold engine; When the engine first starts up, the remaining oil gets absorbed down into the combustion chamber by the bad seal.
  • It generates a high vacuum in the engine; the oil gets absorbed by the seal and then burns in the exhaust causing the lawnmower smoking and leaking oil from the exhaust.
  • Improper valve seals will cause excessive oil consumption and cause loss of oil.
  • It can cause long-lasting excessive smoke after startup and acceleration.

Ways to Avoid Grey Lawn Mower Smoking and Leaking Oil From Exhaust:

A leaking valve stem seal can contribute to damage and failure in your engine. Follow the mentioned steps to avoid oil leakage and to prevent smoke from the exhaust;

  • Add an oil stop-leak additive to the oil filter tube of the engine for a temporary fix and extended life.
  • Use a high mileage motor oil that has seal conditioners in them to reduce corrosion and stop oil leakage.
  • Replace the leaking seal. Apply gasket sealer on both sides of the new cork-made gasket. The rubber gasket doesn’t need any seal.


Maintaining a lawnmower is as essential as lawn maintenance. We have tried to help you with lawnmower smoking and leaking oil from exhaust problems and all the factors that cause such issues.

We hope the provided reasons, causes, symptoms, and possible solutions for this specific issue will be helpful for you in maintaining your lawnmower, avoiding smoking, and preventing oil leakage from the exhaust.

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