In this post, we’ll look at what symptoms to look for to know when an ATV is overheating, the most common causes for overheating problems, and what you can do to prevent it from happening.
How to tell if your ATV is overheating? Look for these 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 especially important to pay attention is 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 on the instrument cluster has turned on
Most ATVs have a lamp that will flash or turn 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. There is noticeable power loss
Modern ATVs will automatically reduce engine power whenever an overheating issue lasts for more 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. The engine feels much warmer 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 be paying attention to the engine temperature consciously, but your body will still pick up when there is a change, and something doesn’t feel like normal.
Caution! Do not touch the engine with your bare hands, as it may be scolding hot.
5. You hear a ticking noise in the engine due to oil burning off
When engine temperatures get too hot, it may burn away oil meant to lubricate the engine’s internals. This may cause the engine to start making a ticking noise that speeds up as you rev the bike.
6. There is steam coming from the radiator area
Coolant should not reach the boiling hot temperatures in normal riding situations. It is boiling coolant coming from the radiator or a leak in a coolant hose if you steam.
7. There is a sweet smell due to the hot coolant/antifreeze
Coolant contains sweet-smelling (but toxic) ethylene glycol. As it reaches boiling hot 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 as long as you catch it early.
The serious problem comes when you allow the coolant to keep boiling. 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 of these increase friction until the pistons seize completely, causing permanent damage to the cylinder walls. When you begin hearing ticking sounds from the engine, you know that 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 or even if you managed to stop the bike before the pistons seized completely.
- 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 planed.
What causes an ATV to overheat, and how do you stop it from happening?
Hopefully, this general troubleshooting guide will point you in the right direction to better identify what underlying problem is 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 ones that are most common with ATVs and those that are easiest and cheapest to fix.
1. The radiator is clogged or dirty
A clogged or dirty radiator or radiator screen is likely the number one cause of overheating ATVs.
The radiator needs a constant flow of cool air for it to dispose of the engine heat properly. 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.
Also, the radiator fins may get clogged with dirt, creating an insulating layer between the hot metal and the cool air.
Make sure also 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 wet and flush away 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 will.
2. The thermostat is bad and stuck closed
The thermostat is a heat-sensitive valve that regulates the flow of coolant through the cooling system. As temperatures begin to rise to a point where the engine needs more cooling, the valve will open 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. Making sure you always run fresh and high-quality coolant will reduce the risk of your thermostat corroding.
Thermostats are cheap and easy to replace, as well as a common cause of engine overheating. Whenever you are faced with overheating issues, a thermostat replacement should be high up on the list.
3. The ATV is low on coolant due to leaks in the cooling system
The coolant fluid level needs to 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, which indicate 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 shouldn’t be necessary to regularly add more coolant as a bike in good mechanical shape won’t use or burn coolant under regular use. But to prevent possible overheating issues and other problems down the line, it’s always a good precaution to inspect the coolant level before each ride.
If the coolant is running low, you may suspect that there is a leak somewhere. Look for wet spots on your radiator, as they are a common source for leaks.
A mechanic will be able to 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. Just a small leak with the occasional drop will be enough to drain the coolant below 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, keep in mind that it will evaporate faster than when mixed with coolant.
4. The coolant is underperforming and should be replaced
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.You are using the wrong type or wrong mixture of coolant
Your user manual should specify what type of 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. The radiator fan is faulty
Most modern ATVs have a radiator fan that activates when the engine starts getting hot. Its job is to pull cool air across the radiator to improve its efficiency.
The fan can be either mechanical or electric, where 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.
The fan clutch typically fails on a mechanical fan, where on an electrical fan, it’s the fan motor itself.
More common than a failed fan motor is a failed fan sensor, usually located near the top or bottom of the radiator. 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. A low battery voltage is preventing the radiator fan from running
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 bikes cooling system significantly less effective.
You will need a multimeter or voltmeter to check your battery and charging system.
When the ATV is running, you should get a reading of 14.0 to 14.5 volts when measuring on the battery. Any reading lower than this, and the battery may not be able to power the fan.
There is a range of possible culprits to look into when your battery is not charging as it should.
8. A faulty water pump or impeller is preventing proper cooling
The water pump aims to create a consistent flow of coolant through the ATVs cooling system.
A set of rubber coolant hoses connects 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 it gets pumped back into the engine again.
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.
Follow these simple steps to test if the water pump is working correctly:
- Rund the ATV for a minute or two so that the coolant gets lukewarm. 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 the clamp as it may be a bit firm.
- Put the loose end of the hose in a clean container.
- Start the engine. If the pump is working correctly, you should see a steady stream of coolant flowing into the pan.
- 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 is 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. A broken head gasket may be causing a coolant loss
If the head gasket breaks, the coolant will enter the combustion chamber, where it will burn off or mix with the engine oil.
Depending on where the gasket has failed, you may or may not see water in the oil. The engine oil will turn to a caramel light brown when contaminated with coolant.
White exhaust smoke is a typical sign that water is entering the combustion chamber. You may even smell the sweet smell of burnt coolant.
In both cases, the coolant level will drop, effectively 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. The radiator is damaged, causing poor cooling performance
A radiator consists of a network of small 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 is causing the ATV to run hot
A carb that is not set up correctly, with a too lean fuel/air mixture, may cause the bike to run hotter than usual.
So may a valve timing that is off, valves that are too tight, as well as using incorrect spark plugs.
An engine running hotter than usual is more prone to overheating as you start adding load or running it 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.
14. Prolonged idling is 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
Except for making sure the ATV is in good working order regarding the common types of issues listed above, here are a few tips on how you can prevent your ATV from overheating.
Make sure the radiator is always clean
The number one thing you can do to prevent your ATV from overheating is to regularly clean the radiator and radiator screen.
Please refer to the step by step guide above to learn how to clean the bikes cooling system properly without damaging it.
Make sure the coolant is fresh and doesn’t need to be replaced
Replacing the coolant is often a neglected aspect of some people’s ATV maintenance schedule.
Use a tester every few months to make sure 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 ATVs today come stock with radiator fans, it’s a great upgrade if your bike doesn’t have one.
If your bike has a mechanical fan, consider upgrading to an electrical 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 does. 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 winter months hit.
For racing: Install a high-pressure radiator cap if you are running 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 is used to raise the boiling point and prevent 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 that you use 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 that using another 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. Using 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 an ethylene-glycol based and aluminum compatible. However, it is recommended that you flush the system and add coolant according to manufacturer spec 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
ATV engines typically run at 200F to 240F (93C to 115C) when measuring the oil temp.