Key Takeaways
- Driving with low coolant can cause your engine to overheat, leading to severe damage such as pistons welding to cylinders or a complete engine failure.
- Low coolant levels can also result in blowing a head gasket, which is indicated by smoke from the engine or tailpipe and decreased engine performance.
- Some vehicles may automatically shut off the engine to prevent severe damage when the coolant is too low, which can be dangerous if it happens while driving.
- Signs of low coolant include a high-temperature gauge reading, malfunctioning A/C, and a sweet-smelling odor from leaking antifreeze.
Gasoline engines, diesel engines, hybrid vehicles, and even electric cars naturally create heat. When your engine is running, and you use your car’s heater, much of this heat is sent to the passenger cabin. However, the rest of the heat is managed another way.
To ensure the engine stays at an optimal operating temperature, your car relies on a fluid called antifreeze. Antifreeze is mixed with water to become engine coolant. Driving with low coolant could let your engine get too hot, which usually spells trouble for your engine, your vehicle, and your driving journey!
 
EFFECTS OF LOW COOLANT IN CAR
Driving with low coolant can damage certain parts of your vehicle, which could require major repairs. Here are some things that can happen if you drive with low coolant.
YOUR ENGINE COULD OVERHEAT.
One of the most immediate and severe consequences of low coolant is engine overheating. Coolant helps pull heat away from the engine. So, without enough coolant, the engine could overheat or seize up. Continued use of an overheated engine could lead to permanent damage, such as pistons welding to the cylinders and complete engine failure.
YOU COULD EXPERIENCE REDUCED FUEL EFFICIENCY.
Low coolant levels may also impact your vehicle’s fuel efficiency. When the engine operates at higher temperatures than designed, it may pre-ignite or detonate the fuel and run less optimally. This can result in increased fuel consumption as the engine works harder to maintain performance.
YOU COULD BLOW A HEAD GASKET.
If you’ve ever said, “I am about to blow a gasket,” to describe your mood — you know that this happening to your engine is bad news! The head gasket is a crucial seal between the engine block and the cylinder head, preventing coolant and engine oil from mixing and ensuring the engine maintains proper compression.
Low coolant can sometimes cause a head gasket on your engine block to blow. If this happens, you may notice smoke emitting from the engine or tailpipe, a loss of power, engine knocking sounds, or decreased efficiency.
YOUR CAR COULD SHUT OFF.
Some cars have a safety system in place to automatically shut the engine off before it suffers significant damage — which can happen due to low coolant. While this may help save you from extensive repairs stemming from an overheated engine, it can be very dangerous depending on where you are driving when the engine shuts off.
LOW COOLANT SYMPTOMS
Recognizing the symptoms of low coolant early may help prevent more severe damage to your vehicle in the long term. However, low coolant symptoms can vary depending on how low your vehicle is on coolant.
Typically, low coolant will trigger your coolant light. Some vehicles might display a “Check Coolant” message on the dashboard. If your coolant light is on, you may notice some of these oddities.
THE HIGH-TEMPERATURE GAUGE IS NEAR OR IN THE RED.
One tell-tale sign of low coolant is the high-temperature gauge on the dashboard. This gauge is designed to tell you when the engine is getting too hot. Most often, the gauge should stay near the center of the H and C symbols.
If you notice the needle moving towards the H, this could indicate that your engine is overheating. In this scenario, pull over safely, shut your engine down immediately, and have it towed to a Firestone Complete Auto Care near you for repairs.
THE A/C SYSTEM IS MALFUNCTIONING.
When you use your vehicle’s heat, the coolant helps regulate the flow of hot air into the cabin. If the coolant is low and your air conditioning is running, you may notice hot air coming from your car A/C vents.
THERE’S A SWEET-SMELLING ODOR.
When there’s a coolant leak in your vehicle, you may notice a sweet smell in your air conditioning or under the hood. This is because antifreeze typically contains glycols and other liquid chemicals that are sweet but poisonous. These are used to help regulate the freezing and boiling point of water. While strange odors may be a sign of car issues, they are not always a clear indicator. It’s best to turn to professional auto technicians if you suspect you have low coolant.
YOUR COOLANT LEVEL SENSOR IS FAULTY.
Sometimes, an illuminated coolant light may be due to a faulty coolant level sensor. If this sensor malfunctions, it could be causing the coolant light to turn on even if you don’t have low coolant levels. Even worse, it might not recognize low coolant levels either.
CAUSES OF COOLANT LOSS
Unlike engine oil, which used to be changed as frequently as 3,000-5,000 miles, you normally don’t have to check and replace coolant as often. In fact, since coolant works within a closed system, it shouldn’t become low unless there’s a leak, in which case you should visit your local car care technicians for radiator services and repairs.
There are a few common ways in which coolant fluid can drop to low levels:
EXTERNAL LEAKS
Leaks are the most common cause of coolant loss. These can occur in various parts of the cooling system, including external leaks from radiator hoses, connections between hoses, or from the radiator itself.
INTERNAL LEAKS
A failing head gasket or other internal leaks can cause coolant to escape into the engine or exhaust system. Leaks are a serious issue that requires immediate attention.
FAULTY RADIATOR CAP
The radiator cap maintains pressure in the cooling system. If the cap is damaged or not sealing properly, it can allow pressurized coolant to leak out.
COOLANT SERVICES AT FIRESTONE COMPLETE AUTO CARE
Regular maintenance is key to preventing coolant-related issues. Have your cooling system inspected and serviced according to its manufacturer-suggested maintenance schedule. This includes checking coolant levels, inspecting hoses and the radiator, and ensuring the radiator cap is functioning correctly.
If you suspect that your vehicle has a coolant leak, visit a Firestone Complete Auto Care near you for a Complete Vehicle Inspection Plus, where we’ll test your coolant pressure. Beyond the inspection, we’ll diagnose your low coolant issue, recommend the necessary repairs, and get you back on the road with a car that’s Fixed Right. Priced Right. Right on Time.