In this post, we’ll look at what symptoms to look for to know when an ATV is overheating, the most common causes of overheating problems, and how to prevent it.
ATV Overheating Symptoms
When an ATV begins to overheat, it will give you various warning signs that tell you something is not quite right.
By knowing what signs to look out for, you are more likely to become aware of a potentially harmful issue before it has a chance of causing permanent damage.
It is vital to pay extra attention in riding situations where the ATV is extra prone to overheating, such as when:
- Pulling heavy at slow speeds
- Mudding with oversized tires
- Riding in hot climates
Here are some typical signs and symptoms that may indicate the ATV is starting to overheat.
1. The “Overheat” Warning Light Turns On
Most ATVs have a lamp that flashes or turns on to indicate an overheated engine. A sensor mounted on the cylinder monitors the engine’s temperature and activates the light when it reaches a set value.
If your high temp light turns on, but all systems seem to be working as usual, and you don’t find any other signs of overheating, you may only have a bad sensor.
2. A Noticeable Power Loss
Modern ATVs will automatically reduce engine power whenever an overheating issue lasts longer than a short period.
3. Fluid Leaks (Oil or Other Fluids)
As the engine temperature rises, the viscosity in oils and other fluids decreases (thins), pressure increases, and metal parts may start warping, causing leaks. If you notice fluids dripping from underneath the ATV, it’s a sign that things are getting way too hot.
4. Engine Feels Much Hotter Than Normal
That’s right; you will likely feel when the engine is becoming warmer than usual. After all, you sit with the engine in between your legs.
You usually won’t consciously pay attention to the engine temperature, but your body will still pick up when there is a change, and something doesn’t feel normal.
Caution! Please do not touch the engine with your bare hands, as it may be scolding hot.
5. Engine Ticking Noises
When engine temperatures get too hot, oil meant to lubricate the engine’s internals may burn away. This may cause the engine to start making a ticking noise that speeds up as you rev the bike.
6. Steam From the Radiator Area
Coolant should not reach boiling-hot temperatures in typical riding situations. If you see steam, it is boiling coolant from the radiator or a leak in a coolant pipe.
7. A Sweet Smell of Hot Coolant
Coolant contains sweet-smelling (but toxic) ethylene glycol. As it reaches boiling temperatures, it may start leaking out of the cooling system, releasing its maple syrup-like smell.
Overheating Can Cause Permanent Damage to Your ATV
If you suspect that your ATV is starting to overheat, you should stop immediately and try to identify what is causing it. Prolonged overheating may cause permanent damage to the engine if left unaddressed.
The key to preventing overheating damage is to catch it early, get the ATV cooled off, and fix whatever issue is preventing the bike from staying cool.
There are several stages of overheating. At the lower end of the scale, you have situations where the bike seems to run a bit hotter than usual, the fan may run more than you’re used to, but the temp never gets so high that the coolant starts boiling.
When things get so hot that the coolant boils, it’s definitely time to take a break to let things cool off. Boiling coolant usually won’t cause any damage if you catch it early.
The severe problem comes when you allow the coolant to keep boiling. The boiling coolant evaporates, gradually reducing the cooling system’s ability to keep the bike cool. As more coolant evaporates, the risk of severe damage increases.
Then there is the factor of what is causing the bike to overheat, where some issues are more prone to causing permanent damage than others.
Overheating left unattended may cause damages to your ATV, such as:
- When the engine runs too hot, oil begins to burn off, causing a gradual lubrication loss. Also, increased temperatures will cause metals to expand. Both increase friction until the pistons seize completely, causing permanent damage to the cylinder walls. When you hear ticking sounds from the engine, you know this process is well on its way, and the pistons are close to seizing. At this point, the engine will likely need a complete rebuild, even if you managed to stop the bike before the pistons seized utterly.
- Metal parts, such as the cylinder head, may warp, causing friction or loss of compression to a point where the engine will barely run. The cylinder head needs to be replaced or may, in some cases, be reused after being planned.
Common Causes of an ATV Overheating
Hopefully, this general troubleshooting guide will point you in the right direction to better identify the underlying problem causing your ATV to keep overheating.
One or several of the issues listed below may be present. Your best bet is to start at the top as we begin with the most common ones with ATVs and those that are easiest and cheapest to fix.
1. Clogged or Dirty Radiator
A clogged or dirty radiator or radiator screen is likely the number one cause of overheating ATVs.
The radiator needs a constant cool airflow to properly dispose of the engine heat. When mud and debris from off-roading, swamp riding, or dirt road riding get lodged in the radiator screen, it prevents the cold air from reaching the radiator.
The radiator fins may also get clogged with dirt, creating an insulating layer between the hot metal and the cool air.
Don’t forget to inspect the back of the radiator, as it is commonly overlooked. It doesn’t matter if the front is clean when the back is caked with mud and dirt.
This is how you properly clean your radiator to prevent overheating:
- If your ATV has a detachable radiator screen, remove it and clean it using a garden hose or a pressure washer. Do not use a pressure washer if you can’t remove the screen, as it may damage the radiator fins.
- Use a garden hose to remove dirt and debris from the radiator fins. Again, please do not use a pressure washer as it may deform the fins, permanently reducing the radiator’s cooling efficiency.
- Also, clean the engine exterior using a brush and a garden hose. A dirty engine will not dispose of the heat as efficiently as a clean engine.
2. Faulty or Stuck Thermostat
The thermostat is a heat-sensitive valve that regulates the coolant flow through the cooling system. As the temperature rises to a point where the engine needs more cooling, the valve opens to allow coolant to pass through the radiator.
If the thermostat gets stuck in the closed position, the coolant will no longer pass through the system. Thermostats are considered consumables that tend to get stuck after a few years due to corrosion. Ensuring you always run fresh and high-quality coolant will reduce the risk of your thermostat corroding.
Thermostats are cheap, easy to replace, and a common cause of engine overheating. Whenever you are faced with overheating issues, a thermostat replacement should be high up on the list.
3. Low Coolant Levels
The coolant fluid level must be within a specified range for the cooling system to work correctly.
On the side of the coolant reservoir tank (also known as the recovery bottle), you’ll find max and min marks indicating the correct coolant level. The coolant level should be within the maximum and minimum marks when the engine and coolant are cold.
Add more coolant according to the manufacturer’s recommendations if necessary.
It should not be required to continually add more coolant, as a vehicle in sound mechanical condition should not consume or burn coolant during regular operation. But to prevent overheating issues and other problems down the line, inspecting the coolant level before each ride is always a good precaution.
If the coolant is running low, you may suspect a leak somewhere. Look for wet spots on your radiator, as they are a common source of leaks.
A mechanic can pressure test the cooling system to identify where the leak is occurring.
Other possible places where you may find coolant leaks are:
- The rubber coolant hoses
- The area around the water pump
- The thermostat housing
- The head gasket
- The freeze plugs
Note 1: There won’t always be a large, clearly visible leak. A small leak with the occasional drop will drain the coolant below the minimum over time.
Note 2: Coolant is not only used for its antifreeze and anti-corrosive abilities; it also prevents the water from evaporating. If you’re in a pinch and decide to use only water as a coolant, remember it will evaporate faster than when mixed with coolant.
4. Poor Coolant Quality
Coolant can go bad over time or lose some of its efficiency due to contamination.
It’s recommended that you completely drain the system and add a new coolant according to manufacturer recommendations every five years. This will ensure that the coolant maintains its ability to protect the engine.
5. Incorrect Coolant Mixture
Your user manual should specify what coolant to use and what distilled water/coolant concentration you should use on your bike. For optimal performance, you should typically use a 50/50 or 60/40 mix.
If the coolant mixture is off, it will negatively affect the bike’s ability to prevent overheating. Use an antifreeze tester to test your concentration, or if you are overdue on scheduled maintenance, do a complete system flush to add new coolant according to spec.
6 Defective Radiator Fan
Most modern ATVs have a radiator fan that activates when the engine gets hot. Its job is to pull cool air across the radiator to improve efficiency.
The fan can be mechanical or electric, whereas the latter type is most common on ATVs.
A working fan makes an audible sound that can’t be missed when it kicks in. If your fan is not starting, you can test if it works by jumping the fan motor directly from the battery. This should start the fan motor instantly. Make sure you keep your hands at a safe distance from the spinning fan blades.
Typically, the fan clutch is the component that fails in a mechanical fan, whereas, in an electric fan, it’s usually the fan motor that becomes defective.
A failed fan sensor, typically located near the top or bottom of the radiator, is generally more common than a failed fan motor. Some earlier models had the sensors minted in the center of the radiator. This little sensor tells the fan when to start and when to stop.
7. Low Battery Voltage Prevents the Radiator Fan From Working
Your ATV needs a working charging system and a healthy battery for the radiator fan to work correctly (electrical fans). If your battery voltage is too low, it won’t have the power to run the fan motor, leaving the bike’s cooling system significantly less effective.
You will need a multimeter or voltmeter to check your battery and charging system.
When the ATV runs, you should get a reading of 14.0 to 14.5 volts when measuring the battery. Any reading lower than this and the battery may be unable to power the fan.
There are many possible culprits to look into when your battery is not charging as it should.
8. A Faulty Water Pump or Impeller Prevents Proper Cooling
The water pump aims to create a consistent coolant flow through the ATV’s cooling system.
Rubber coolant hoses connect the radiator, coolant reservoir, and engine to form a closed cooling circuit. The water pump transfers hot coolant from the engine and over to the radiator, where it cools down before getting pumped back into the engine.
When the water pump fails, the hot coolant will not reach the radiator but remain in the engine. This can cause the engine to overheat.
This is how to test if the water pump is working correctly:
- Run the ATV for a minute or two to lukewarm the coolant. Then stop the engine.
- Pull the return hose from the radiator by compressing the hose clamp; you may need to use a pair of tongs to squeeze it as it may be a bit firm.
- Put the loose end of the hose in a clean container.
- Start the engine. If the pump works correctly, you should see a steady stream of coolant pouring into the container.
- Stop the engine, reinstall the coolant hose, and pour the coolant back into the radiator or coolant reservoir.
If the pump does not work, it may be as simple as fastening an impeller nut that has come loose or replacing a cracked or chipped impeller. In some cases, there are leaks, wear, or corrosion to a level where the water pump needs to be replaced.
9. Trapped Air Preventing Proper Coolant Circulation
Trapped air pockets may prevent proper coolant flow throughout the cooling system. Some ATVs have a bleed screw on top of the head that needs to be bled after replacing the coolant.
10. Broken Head Gasket Causing a Coolant Loss
If the head gasket breaks, the coolant will enter the combustion chamber, where it burns off or mix with the engine oil.
You may or may not see water in the oil, depending on where the gasket has failed. When contaminated with coolant, the engine oil will turn to a caramel light brown.
White exhaust smoke is a typical sign of water entering the combustion chamber. You may even smell the sweet smell of burnt coolant.
In both cases, the coolant level will drop, increasing the likelihood of the ATV overheating.
Other times exhaust gasses will enter the cooling system, resulting in air pockets trapped in the water pump, preventing proper coolant circulation. If you notice exhaust gasses in the coolant overflow tank, it’s a sure sign of a failed head gasket.
If you suspect you have a head gasket failure, you can test it by performing a compression test or, even better, a leak-down test.
Do not drive with a blown head gasket, as it can result in additional engine damage from overheating or reduced lubrication.
11. Damaged Radiator, Causing Poor Cooling Performance
A radiator consists of a network of tiny tubes or canals containing the liquid antifreeze and a mesh of small cooling fins that maximize the surface area between the hot coolant and the cool air.
The cooling fins are fragile and may get damaged from dirt getting lodged between them or spraying them aggressively with a pressure washer.
A radiator with too many damaged cooling fins will not be as efficient as it may need to be, leaving the ATV to overheat sooner than usual.
12. Improper Engine Tuning Causing the ATV to Run Hot
An improperly adjusted carb, with a too-lean fuel/air mixture, may cause the engine to run hotter than usual.
Similarly, inaccurate valve timing, excessively tight valves, or incorrect spark plugs can also contribute to this issue.
An engine that runs at higher temperatures than usual is more susceptible to overheating, especially when subjected to additional load or operated in hot climates.
13. The Cooling System Can’t Keep up When Riding on a Hot Day
For those that ride in scorching climates, the bike’s cooling system cannot keep up with the heat, even under moderate loads.
Even riding on a hot day can overwhelm the cooling system, no matter how new and high-quality the coolant is.
14. Prolonged Idling Causing Air-Cooled ATVs to Overheat
Some small or medium-sized ATVs don’t have a liquid cooling system with a radiator but are equipped with air-cooled engines.
An air-cooled engine needs airflow across the fins of the cylinder head to dissipate heat properly. When idling, especially in hot conditions, the engine may overheat simply from a lack of moving air across the engine surface.
It is recommended to stop an air-cooled ATV any time you expect idling for more than a minute or two.
How to Improve Cooling and Prevent ATV Overheating
In addition to ensuring your ATV is in good working order concerning the common issues mentioned above, here are a few tips to prevent your ATV from overheating.
Ensure the Radiator Is Always Clean
The number one thing you can do to prevent your ATV from overheating is regularly clean the radiator and radiator screen.
Please refer to the step-by-step guide above to learn how to properly clean the bike’s cooling system without damaging it.
Ensure the coolant is fresh and doesn’t need to be replaced
Many people often overlook the replacement of coolant in their ATV maintenance schedules.
Use a tester every few months to ensure the coolant is healthy and has the right mixture. Change the fluid according to your manufacturer’s recommendations, usually every two to five years. A complete system flush usually takes less than an hour.
Install an Electrical Radiator Fan
While most of today’s ATVs come with radiator fans, it’s an excellent upgrade if your machine doesn’t have one.
If your bike has a mechanical fan, consider upgrading to an electrical one, as it will not negatively impact horsepower or fuel economy as a mechanical fan does.
Install an Aftermarket Water Pump and Impeller
Some manufacturers offer aftermarket water pumps that provide a better capacity than the stock. This may be an option to look into for those that need extreme cooling.
Use “Water Wetter” When Riding in Scorching Climates
A tip commonly found on dune-racer forums uses a mix of a product called “Water Wetter” combined with distilled water. This mix is supposed to provide even better cooling than a regular 50/50 antifreeze/water mix. It even contains corrosion inhibitors and should be safe to use as long as you remember to replace it before the winter months hit.
Install a High-Pressure Radiator Cap if You Use Little to No Coolant
Racers often run pure water or a mixture with little to no coolant. They do so to increase cooling since water transfers heat better than any coolant mix or because circuit rules prevent them from running with glycol-based coolant.
Water, however, has a lower boiling point than a water/antifreeze mix. A high-pressure radiator cap raises the boiling point and prevents the system from boiling.
Note that a high-pressure radiator cap will not help to prevent overheating on a stock system.
What Is the Best ATV Antifreeze?
Most ATV manufacturers recommend using a 50/50 antifreeze premix, while others suggest a 60/40 mix. You will never go wrong by using the type recommended by the manufacturer, but other quality brands will likely work just as well. Note using a different antifreeze than the manufacturer recommends may void the warranty.
Make sure the coolant you choose is aluminum compatible. Also, make sure to use distilled water if you’re not using a premix. Regular water may cause mineral deposits inside the engine and radiator over time.
Can You Use Car Antifreeze in ATV?
You can use car coolant in an ATV as long as it is ethylene-glycol-based and aluminum compatible. However, it is recommended that you flush the system and add coolant according to manufacturer specs when possible.
What Type of Coolant Does an ATV Use?
ATVs use an aluminum-compatible ethylene glycol-based coolant mix. Do not use propylene glycol or mix propylene glycol with ethylene glycol.
How Hot Do ATV Engines Get?
When measuring the oil temp, ATV engines typically run at 200F to 240F (93C to 115C).