Getting a big cloud of white smoke can be scary. Most people don’t expect it to happen — but why is it even happening?
If your mower is blowing white smoke, it’s likely due to a damaged head gasket, a clogged air filter, or overfilled oil. To resolve the problem, check the oil level and ensure that it’s not overfilled. If it is, drain the excess oil and refill it to the correct level. Next, inspect the air filter and replace it if it’s dirty or clogged. If these solutions don’t work, the head gasket may be damaged and require replacement. It’s best to take the mower to a qualified technician for repair.
Common Reasons a Lawn Mower Is Blowing White Smoke
If your lawn mower is blowing white smoke, it indicates a potential issue with the engine. Several common reasons for white smoke coming from a lawn mower are:
- Burning Oil: The most common reason for white smoke is burning oil. If oil leaks into the combustion chamber, it will burn along with the fuel, producing white smoke.
- Overfilled Oil: If you recently changed the oil and accidentally overfilled the engine, it can lead to excess oil getting into the combustion chamber and causing white smoke.
- Worn Piston Rings: Worn or damaged piston rings can allow oil to enter the combustion chamber, leading to white smoke during operation.
- Crankcase Ventilation Issues: If the crankcase ventilation system is clogged or malfunctioning, it can cause pressure buildup in the engine, forcing oil into the combustion chamber and producing white smoke.
- Head Gasket Failure: A blown head gasket can allow coolant to enter the combustion chamber, resulting in white smoke, often with a sweet smell.
- Water or Moisture in the Fuel: If there’s water or excess moisture in the fuel tank, it can create white smoke as it burns with the fuel.
- Fuel Additives or Detergents: Some fuel additives or detergents may create white smoke as they burn.
- Dirty Air Filter: A dirty or clogged air filter can cause an improper air-to-fuel ratio, leading to incomplete combustion and white smoke.
- Incorrect Fuel-to-Oil Ratio: If you are using a 2-stroke engine with a fuel-oil mixture, an incorrect ratio can result in white smoke.
- Choke Stuck On: Leaving the choke on while the engine is running can create white smoke due to excessive fuel being burned.
If you notice white smoke coming from your lawn mower, it’s essential to address the issue promptly to prevent further damage to the engine. You may want to consult the mower’s manual or seek assistance from a professional mechanic or a lawn mower repair service to diagnose and fix the specific problem.
How to Fix the Most Common Causes of White Smoke in Lawn Mowers
To fix the most common causes of white smoke in lawn mowers, you’ll need to perform some troubleshooting and maintenance tasks. Here’s a step-by-step guide to address each potential issue:
- Burning Oil:
- Check the oil level: Ensure the oil level is correct according to the manufacturer’s recommendations. If it’s overfilled, drain the excess oil.
- Inspect for leaks: Look for any oil leaks around the engine and repair or replace any damaged gaskets or seals.
- Replace worn piston rings: If the piston rings are worn, you may need to take the mower to a professional for repair.
- Overfilled Oil:
- If you recently changed the oil and overfilled it, drain the excess oil to the correct level.
- Worn Piston Rings:
- This is a more complex issue that requires professional repair. Take the lawn mower to a qualified mechanic for diagnosis and replacement of the piston rings.
- Crankcase Ventilation Issues:
- Inspect the crankcase ventilation system for blockages or malfunctions. Clean or replace the ventilation components as needed.
- Head Gasket Failure:
- A blown head gasket is a significant issue that requires professional repair. Take the lawn mower to a mechanic to replace the head gasket.
- Water or Moisture in the Fuel:
- Drain the fuel tank and replace it with fresh, clean fuel. Consider using a fuel additive designed to remove water from the fuel system.
- Fuel Additives or Detergents:
- If the white smoke is a result of the fuel additives, switch to a different brand or type of fuel.
- Dirty Air Filter:
- Remove the air filter and clean or replace it, depending on its condition. A clean air filter ensures proper air-to-fuel ratio for combustion.
- Incorrect Fuel-to-Oil Ratio:
- If you have a 2-stroke engine, ensure you are using the correct fuel-to-oil mixture as recommended in the lawn mower’s manual.
- Choke Stuck On:
- Ensure the choke is in the proper position for normal operation. If it’s stuck on, free it up or adjust it as needed.
If you are not comfortable performing these tasks yourself or the issue remains unresolved after attempting these fixes, it’s best to take the lawn mower to a qualified mechanic or a lawn mower repair service for a thorough inspection and proper repair. Regular maintenance and proper care can help prevent many of these issues, so it’s essential to follow the manufacturer’s recommendations for maintenance intervals and procedures.
White smoke tends to be concerning, but it’s usually an easy fix. Far more dangerous for your lawnmower is blue or black smoke. With white smoke, it’s just a matter of fixing a simple issue and letting the engine run until the smoke is no longer there.
Keep in mind that new lawnmowers tend to blow white smoke for a while until they get started and adapt to everything. So, don’t get alarmed if you see this on your first mowing round with your new mower.
ReadyToDIY is the owner of this article. This post was published on May 25, 2020.