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Home / Symptoms / Car Overheating

Four common causes for vehicle overheating and their related parts.

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Is Your Car Overheating?

An overheating car sends obvious signs of danger: steam from the hood, foul smells, and the frightening sight of your thermometer in the red zone.

Automobiles are designed with the engine's cooling system to be effective. Engines run off flammable fuel, motioning various parts at incredible speeds. As a result, they generate tremendous heat in the process and need to be cooled to run safely.

Your vehicle has indicators to warn you of an overheating engine, like the engine temperature gauge symbols on your dashboard. Still, even the indicators won't run well if your car's cooling system is working badly.

Your vehicle's systems for regulating engine temperature include fans that run through the engine, the radiator, and the air conditioning system that vents into the interior. This means that engines overheat when heating or AC systems develop an internal temperature control problem.

Watch out: Several issues might lead to overheating, but they're all serious problems. First, overheating vehicles are flat-out unsafe to drive. Fortunately, there are resources at a technician's disposal to find the trouble's root cause.

Let's Get To The Bottom Of It!

Does your vehicle get hot when stopped and cool off when it reaches highway speeds?

You may also see steam from the hood or the temperature warning light illuminating the dashboard.

If your vehicle's cooling fan is powered by electricity, it only comes on when the temperature in the radiator gets hot enough. When working correctly, the fans draw air over the radiator fins and pull heat out of the coolant to cool the hard-working engine. If this fan fails, your engine will overheat. Driving at high speeds will generate enough ram air to cool the car engine, but once you slow down, your vehicle will overheat again.

Does your vehicle's heater not work as well as it used to?

You may also sense a sweet smell from the vents or hear a gurgling sound from the dashboard.

If the engine coolant leaks and drops to a low level, the air gets into the closed system. Since air doesn't transfer heat nearly as efficiently as liquid coolant, the radiator and cooling system no longer dissipate the heat from the engine. Instead, the air rises to the highest point, the heater core. This disrupts your heater and limits its ability to release as much heat as possible.

Does your vehicle heat up rapidly after you start it?

You may also see the check engine light on the dashboard and coolant leaking under your vehicle.

Your vehicle's thermostat regulates engine heat to keep it consistently at the proper operating temperature. It does this by restricting or pulling the coolant flow through the radiator. If the thermostat fails, it gets stuck in an open or closed position rather than allowing a free flow. If stuck closed, the superheated coolant prevents the engine from leaving, leading to rapid overheating.

Does your vehicle get hot after you have been driving for a while?

You may also hear a squealing noise from the belt and have trouble steering as it heats up.

Your vehicle's water pump circulates coolant through the engine, thermostat, and radiator. This transfers the heat from the engine's combustion process to the radiator. If it fails to circulate the coolant, the engine will heat up. However, since the thermostat is still working, some coolant flow will continue so that the engine won't overheat until after a bit of driving.

Do your windows fog up even with the defroster on?

You might feel the floor under the passenger's seat is wet and notice that your car's temperature gauge on the dashboard is in the red zone.

The heater core is a small air box that pulls heat from the coolant into the vehicle's interior. If the heater core leaks, coolant gets in the air box. When hot air flows over the liquid, condensation forms on your windows, making them fog up.

Did your vehicle become hard to steer before it overheated?

You may also have noticed that the heat didn't work well and that the charging or check battery light has been illuminated on the dashboard.

The serpentine drive belt operates accessories attached to the front of the engine. On some vehicles, it runs the water pump. If the belt fails, all the accessories it drives will also fail. The first thing you'll notice is difficulty steering due to the loss of the steering assist system. You may shortly see the vehicle overheating because the water pump no longer circulates coolant through the engine and radiator.

The most common causes of the car overheating

The most common causes for a car overheating:

Low coolant: The coolant is a refrigerant liquid that absorbs the heat from your vehicle’s engine, then goes to a cooling tank, where it gets cold again, and then it returns to the engine. This loop ensures that the engine’s heat is always being absorbed by the coolant, preventing overheating. However, if the vehicle is low on coolant, the engine won’t get rid of all the heat, resulting in an overheating issue.
Faulty thermostat: The thermostat is a component that opens up whenever the engine reaches a specific temperature. Then, when the temperature inside the engine hits a certain mark, the thermostat opens, allowing airflow to cool down the vehicle, making combustion more efficient. However, if the thermostat fails, the temperature goes up, as the heat inside the engine might not leave if the thermostat doesn’t open appropriately.
Leaking heater core: The heater core is a component in the heating system; it basically gets the hot coolant from the engine and uses it to release hot air inside the cabin whenever you turn the heater on. However, if it fails it might release too much hot air inside the cabin, resulting in overheating.
Faulty water pump: The water pump is a motor that pumps coolant into the engine, ensuring the cycle of refrigerant fluid entering the engine, taking out the heat, and returning to the cooling tank. However, if the pump fails, the coolant might not reach the engine properly and remove heat, resulting in a temperature rise.
Faulty cooling fans: The cooling fans are an airflow component that ensures a proper amount of air circulates inside the engine. This circulation is needed so hot air can be replaced by cool air, keeping temperatures safe. However, if the fans fail, airflow goes bad, resulting in a buildup of hot air in the engine, leading to overheating.
Faulty drive belt: The drive belt is a belt that spins while the engine works, using the vehicle’s movement to generate electricity, helping the battery to power everything it needs. An important cooling component that relies on drive belts is the water pump. A faulty drive belt results in water pump malfunction, leading to bad coolant flow and overheating.

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Frequently Asked Questions

Does your vehicle get hot when stopped and cool off when it reaches highway speeds?

You may also see steam from the hood or the temperature warning light illuminating the dashboard.

If your vehicle's cooling fan is powered by electricity, it only comes on when the temperature in the radiator gets hot enough. When working correctly, the fans draw air over the radiator fins and pull heat out of the coolant to cool the hard-working engine. If this fan fails, your engine will overheat. Driving at high speeds will generate enough ram air to cool the car engine, but once you slow down, your vehicle will overheat again.
Does your vehicle's heater not work as well as it used to?

You may also sense a sweet smell from the vents or hear a gurgling sound from the dashboard.

If the engine coolant leaks and drops to a low level, the air gets into the closed system. Since air doesn't transfer heat nearly as efficiently as liquid coolant, the radiator and cooling system no longer dissipate the heat from the engine. Instead, the air rises to the highest point, the heater core. This disrupts your heater and limits its ability to release as much heat as possible.
Does your vehicle heat up rapidly after you start it?

You may also see the check engine light on the dashboard and coolant leaking under your vehicle.

Your vehicle's thermostat regulates engine heat to keep it consistently at the proper operating temperature. It does this by restricting or pulling the coolant flow through the radiator. If the thermostat fails, it gets stuck in an open or closed position rather than allowing a free flow. If stuck closed, the superheated coolant prevents the engine from leaving, leading to rapid overheating.
Does your vehicle get hot after you have been driving for a while?

You may also hear a squealing noise from the belt and have trouble steering as it heats up.

Your vehicle's water pump circulates coolant through the engine, thermostat, and radiator. This transfers the heat from the engine's combustion process to the radiator. If it fails to circulate the coolant, the engine will heat up. However, since the thermostat is still working, some coolant flow will continue so that the engine won't overheat until after a bit of driving.
Do your windows fog up even with the defroster on?

You might feel the floor under the passenger's seat is wet and notice that your car's temperature gauge on the dashboard is in the red zone.

The heater core is a small air box that pulls heat from the coolant into the vehicle's interior. If the heater core leaks, coolant gets in the air box. When hot air flows over the liquid, condensation forms on your windows, making them fog up.
Did your vehicle become hard to steer before it overheated?

You may also have noticed that the heat didn't work well and that the charging or check battery light has been illuminated on the dashboard.

The serpentine drive belt operates accessories attached to the front of the engine. On some vehicles, it runs the water pump. If the belt fails, all the accessories it drives will also fail. The first thing you'll notice is difficulty steering due to the loss of the steering assist system. You may shortly see the vehicle overheating because the water pump no longer circulates coolant through the engine and radiator.

Typical fixes to address the cause(s)

These are typical processes and repair services that fix a check engine light issue

The most common cause: Low coolant

The most common reason for a car overheating is due to low coolant. The coolant is necessary for balancing and managing your vehicle’s temperature. The cooling fluid leaves the coolant tank, where it has been sitting at a cool temperature, then travels to the engine, absorbing its heat, and finally returns to the coolant tank to cool off.

Symptoms it causes: Apart from the vehicle overheating you might notice A/C issues, heater problems, engine misfires, low engine power, etc.
High risk of priority: A low coolant results in your engine overheating, which can lead to damage. The engine can only endure so much temperature, if the heat goes beyond what internal components can endure, your engine starts having issues and can eventually break down.

How exactly does coolant go low?

The coolant level must be checked whenever possible. The fluid doesn’t typically leave the system and won’t require a refill like oil does. However, coolant might leak from damage to coolant hoses, seals, valves, radiators, etc.

Go safe: Ask for a mechanic to inspect your vehicle’s cooling system to investigate if the coolant fluid is low due to surrounding components and if there’s further damage to check out. Many shops do transparent vehicle inspections and lay out your options after investigating your vehicle’s conditions.

What’s a vehicle inspection? It’s “detective work” on your vehicle, checking its systems to see if anything prevents the car from working as expected. In this case, mechanics examine different parts of your vehicle to track if anything is causing the coolant to leak out. They’ll also check the condition of components during their inspection, noting which are causing the problem and which got affected by it, recommending to replace them in order of priority.

Transparency example in a leaking radiator service

A cooling system inspection is the most transparent process to understand why your vehicle’s coolant level is low. This is because many components surrounding the radiator, coolant tank, and cooling hoses can have a say in the issue, indicating the real culprits that caused it all.

Let’s read an example of how this kind of inspection helps to service a low coolant level and solve a vehicle overheating.

A customer dropped off their car concerned that the heater no longer worked well. They said it seemed warm when driving at highway speeds but cooled off almost entirely when they hit stop-and-go traffic. They said that they checked to make sure that the air conditioner wasn't on and that it wasn't, but it felt almost like it was constantly on.

The technician felt the heater was not producing much heat on the test drive.

However, during the vehicle health inspection, the technician noted that the coolant was low and that the radiator was wet from the upper seam, where the core and the tank are crimped together.

The technician performed a cooling system pressure test and verified that the upper tank on the radiator was leaking at the crimp and found no other leaks. The technician recommended replacing the radiator.

Coolant low

In this case, the mechanic put the “Immediate Action” tag on the radiator and coolant level.

Similar Symptoms

Below are just a few examples of typical Symptoms and Fixes your car might be experiencing

Four common causes for weird braking from a vehicle and their related parts.

Is Your Car Overheating?

Let's Get To The Bottom Of It!

The most common causes of the car overheating

Find Professional Help

Frequently Asked Questions

Does your vehicle get hot when stopped and cool off when it reaches highway speeds?

Does your vehicle's heater not work as well as it used to?

Does your vehicle heat up rapidly after you start it?

Does your vehicle get hot after you have been driving for a while?

Do your windows fog up even with the defroster on?

Did your vehicle become hard to steer before it overheated?

Typical fixes to address the cause(s)

The most common cause: Low coolant

How exactly does coolant go low?

Transparency example in a leaking radiator service

Similar Symptoms

Why Is My Car Braking Weird?

Why Is My Car Grinding When I Brake?

Why Won't My Car Start?

Why Is My Engine Sputtering?

Why Is My Steering Wheel Shaking?

Why Is My Transmission Slipping?

Why Does My Car Shake When I Brake?

Why Is My Car's Brake Pad Sticking?

Why Does My Car Struggle To Start in The Cold?

Why Is My Car Not Accelerating?

Why is My Car Jerking When Accelerating?

Why Won't My Car Shift Out Of "Park"?