Lawn Mower Engine Cooling Times Explained

You have spent all afternoon cutting the grass and giving your front yard that pristine look that your neighbors have come to envy. You go to take care of the backyard when your lawn mower decides it is time for a break, and it overheats. I have customers contact me about this all of the time.

How long should you expect to wait until you are up and running? The answer can vary depending on a few different variables.

Engine cooling times vary depending on the engine being air or liquid-cooled, the size of the engine, the age of the oil, and external variables like the temperature outside or the thickness of the grass. Smaller, cleaner, air-cooled engines will cool faster than their larger, dirtier counterparts. 

All lawn mowers are constructed differently and, therefore, will have differing engine cool-down times. Keep reading to learn how to maintain a clean, strong engine that maximizes engine power while keeping cool-down times reasonable. 

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Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.

Why Does My Lawn Mower Overheat?

While researching ways to improve the cooldown time for your lawn mower’s engine, it is vital to try and learn what causes the engine to overheat in the first place. Many factors can cause engines to overheat and malfunction. Some of these causes are:

• Metal expansion
• Low or old oil
• Dirty engine
• Damp and thick grass 
• Old components

As engines run, their components heat up, and the metal that they are made of expands. This expansion can be overwhelming to the system, causing the engine to increase in temperature at a rate that the cooling system cannot keep up with.

Therefore, it is vital to ensure that your engine is clean, has all the proper fuel, and that its components are not overused, run-down, or old.

Clogged air pathways are often a common cause of overheating as well. Large pieces of debris can be lodged in parts of the engine block or even outside of it and block important vents that work as entrance or exit points for air.

Air is important, not only for the reactions needed to make an engine work properly but to keep the engine components cool enough to function at all. 

You will know your lawn mower is overheating if you see smoke or steam rise from the engine cap, the sounds of the engine change to chugging-like noises, or if the lawn mower shuts down completely. 

Read more about overheating problems with our article, “7 Things That Can Cause a Lawn Mower to Overheat“.

How Do I Cool Down My Lawn Mower?

There is not a single fix to cool down all lawn mowers. Every mower is different because they use different engines, and different cooling systems and are used differently by their owners.

While you may keep your lawn short and cut it several times a week, others may only cut their grass once a month. 

This means they will be trimming thicker grass than you, causing their lawn mower to exert more energy and the engine to run harder and hotter. There are several ways to ensure your lawn mower cools down in a reasonable amount of time:

• Let the engine idle
• Change the oil
• Keep the engine clean
• Follow your unit’s instructions
• Research your mower’s cooling system
• Pay attention to external variables

Let The Engine Idle

While it is the simplest solution to a complex problem, letting your lawn mower’s engine idle after using it can help the engine cool down. Idling is a twofold solution to overheating.

First, it allows the oil to flow through the engine and disperse the heat from one part of the engine across the whole engine, allowing it to cool down evenly and faster. 

The second reason idling helps your engine cool down is because it allows the fans in air cooling systems to force air across the surface of your engine and decrease the external temperature. 

Typically, a ten-to-thirty second idling period is enough to aid in engine cool-down. Letting your motor idle too long can cause the oil and engine to heat further, causing a slower cool-down time. 

Idling has several definitions depending on who you ask or which lawn mower manual you read. Whether you let your lawn mower sit stationary after each use before turning the engine off or you decrease the power or speed during your last few minutes of use, both of these can be considered idling. 

Check and Change the Oil

When a lawn mower’s engine is running, certain parts will heat up faster than others. Many mower manuals will advise you to leave your mower running at an idle after each use.

This is so that the oil can do its job in helping disperse the heat of one particular part or section of the engine and evenly distribute the heat across the entirety of the engine. This process is called temperature stabilization. 

When checking your oil, ensure the engine is off for a substantial period so that you do not burn yourself. Use a dipstick or an oil pump to check the levels and color of the oil.

If your oil is dark and grainy, it is too old and can do more harm than good by sticking to engine components and burning, causing more heat. 

Change the engine oil if it is old and dirty, this could have been the cause of your engine overheating or extending the engine cool-down time. After your next use, pay attention to see if your lawn mower cools down at a faster rate. 

Not changing engine oil regularly can cause extensive engine damage. Read more about it in our article, “What If You Don’t Change Oil in Your Mower“.

Keep The Engine Clean

Keeping the inside and the outside of your engine clean is of utmost importance. While you may not have the expertise to ensure the inside of your engine is clear of debris, keeping the external portion of your engine and lawn mower clean is easy and vital to swift cool-down times.

If a build-up of dirt, grime, and grass occur on top of your lawn mower, it blocks the air filtration and cooling systems. If the air cannot be filtered and the air cooling system cannot run properly to help your engine to cool down.

Not only is this bad for your engine, but it is also dangerous. Dried grass can be incredibly flammable, and added to a conductor of heat like an engine is a recipe for disaster.

Follow Your Lawn Mower’s User Manual

Every engine is constructed differently. Every lawn mower runs differently. What may work for some lawn mowers will not work for others. There are no coverall answers when it comes to engine cooling and maintenance. 

Following your lawn mower’s user manual will protect you from voiding any warranties that you may have, as well as safeguard your engine against any problems that may arise from quick fixes or do-it-yourself solutions.

While you may save money in the short term by rigging your custom cooling system or engine parts, you are damaging the integrity of your lawn mower and will most likely end up paying for a brand-new engine or an entirely new lawn mower.

Research Your Lawn Mower’s Cooling System

Depending on the size of your lawn mower and the type of engine it has, you will likely encounter two different cooling systems: air-cooled and liquid-cooled.

Air-cooling systems are by far the most common for non-industrial lawn mowers. Air-cooling systems will be found in many push and riding lawn mowers. Air-cooling systems a fan that pushes air to cooling fins found inside of the engine. These fins keep the air in circulation throughout the engine and cool it down. 

If you have an air-cooling system, and it is probable that you do, keeping the oil clean, and the lawn mower and engine block clean are your best bets at ensuring that it is working properly. Debris can clog the cooling fins and restrict air circulation. 

Liquid cooling systems are much less common. These are typically found in large mowers with heavier engines. Liquid cooling systems are known to be much more effective than air cooling systems, but they are far more expensive and heavier.

If your mower has a liquid cooling system, ensure that you are using the proper coolant and that coolant levels are correct. 

Understanding which type of cooling system is in your lawn mower lets you understand the proper steps to take to make sure your engine is cooling in the correct amount of time. 

Pay Attention to External Variables

It is just as important to note the specifications of your engine and its cooling system as it is to note things like air temperature, the thickness or moisture of the grass you are cutting, and debris that can be problematic if mowed over. 

Your mower’s engine is far more likely to overheat on a day that is 100 degrees than it is on a day that is only 75 degrees.

Therefore, if you find yourself mowing in extreme heat, you should think about how hard you work your mower and for how long the engine can maintain that level of power. 

While you pay attention to those temperatures, think about the other conditions you are putting your lawn mower through. If your lawn is longer and thicker, the engine will have to work harder to compensate for the increase in power needed.

This is also true if there is excess moisture in the grass. Wet grass, like after a rainstorm, requires more power to cut through. The higher the power output, the harder the engine works and the hotter the engine gets. 

If engine components are damaged, your mower’s engine will not function correctly, and overheating will be one item on a very long list of problems. 

Keeping Your Mower Clean for Proper Cooling

Keeping a clean engine is a great way to make sure that your lawn mower can cool down properly. Taking proper precautions and understanding how to appropriately clean the inside of your engine to the best of your understanding without expertise can help extend the life of your mower exponentially. 

Some steps to cleaning your lawn mower engine are:

• Turn the engine off and unplug the spark plug wire
• Remove the engine screen or cover by following the mower’s user manual
• Use a brush and/or a mild washing soap to clean the cooling fins
• Remove any large pieces of debris easily visible

You should avoid using compressed air or long brushes because they can push pieces of debris further into the engine and do more harm than their previous position. 

How Often Should I Clean My Engine?

Cleaning your engine to improve cooling time is a great tactic, but you should avoid doing it too often. Engines are meant to have some presence of grease and grime so that the different metal pieces can interact without scratching or bumping. 

Most user manuals advise doing basic maintenance and oil changes after approximately 50 hours of use. For the average person, this amounts to roughly every two-to-three months, depending on the frequency of your use of the lawn mower. 

If your engine is new, you will need to complete an initial oil change within 7-10 hours of initial use.

Cleaning your engine does not mean a full breakdown and replacement of parts. This refers to simple maintenance of your mower, such as:

• Changing the oil
• Changing air filters
• Adding new spark plugs

It is also important to protect your mower during the “off-season.” If you live in an area where it snows during the winter, you should winterize your lawn mower. This includes making sure that you:

• Drain your mower of gas or add a fuel preservative
• Wash off any visible debris
• Sharpen the blades
• Remove the battery and spark plug
• Store your mower in a dry place for the winter

If you keep your mower in a place where rodents or insects can find their way inside, try and find a way to keep them out.

Placing traps or using a repellent will ensure that mice do not find their way into your mower’s engine and chew through important wires or form nests that clog important air paths. 

Rodents can do a lot of harmful damage to your engine and wiring in your lawn mower. I have had good results with a couple of products by Grandpa Gus’s. I place the packets around my equipment and use the spray on the electrical wires to prevent rodents from chewing on the wires.

Conclusion

Cooling your lawn mower’s engine after strenuous use can be both simple and incredibly complex. You can take all precautions that you can find, but that does not guarantee that you will find the cause of your cooling delays or problems. 

The best thing that you can do is perform regular maintenance. Maintaining a healthy lawn mower engine will give you the best cooling time possible while simultaneously providing the best output in performance.