A car can overheat when the cooling system can no longer remove enough heat from the engine. Common causes include low coolant, coolant leaks, thermostat problems, cooling-fan failures, water-pump problems, radiator restrictions, and other cooling-system faults.
ENGINE OVERHEATING GUIDE
Why Is My Car Overheating?
Overheating should be taken seriously. Continuing to drive an overheating vehicle can turn a cooling-system problem into much more expensive engine damage.
The temperature gauge or warning message tells you that the engine is getting too hot, but it does not identify which component has failed.
The cooling system should be inspected and tested before parts are replaced.
COMMON CAUSES
8 common causes of car overheating
An overheating engine can have several possible causes. The symptom tells you there is a cooling problem, but proper diagnosis is still needed to identify the actual failure.
01
Low coolant
The cooling system relies on the proper amount of coolant to absorb heat from the engine and transfer that heat to the radiator.
If the coolant level becomes too low, the system may not be able to control engine temperature properly.
If the level keeps dropping, the important question is why.
02
Coolant leak
A coolant leak can gradually lower the coolant level until the engine begins running hotter than normal.
Possible leak points include radiator hoses, radiator, thermostat housing, water pump, reservoir, heater hoses, fittings, and other cooling-system components.
Some leaks only appear when the system is hot and pressurized.
03
Bad thermostat
The thermostat regulates coolant flow between the engine and radiator as the engine reaches operating temperature.
If it does not open correctly, coolant circulation can be restricted and engine temperature can rise quickly.
04
Cooling fan problem
The radiator fan helps move air through the radiator when natural airflow is not enough, especially while the vehicle is stopped or moving slowly.
A failed fan motor, relay, fuse, wiring issue, sensor, or control problem can prevent the fan from operating when needed.
05
Water pump problem
The water pump circulates coolant through the engine, radiator, and cooling system.
A pump can develop an external leak, bearing problem, or internal circulation issue depending on its design and failure mode.
06
Radiator problem
The radiator transfers heat from the engine coolant to the outside air.
Restricted coolant flow, damaged fins, external blockage, internal restriction, or another radiator problem can reduce the system’s ability to remove heat.
07
Cooling-system pressure problem
Automotive cooling systems operate under pressure. Proper pressure helps coolant operate at the temperatures required by the engine.
A leaking pressure cap, damaged reservoir, hose problem, or another pressure-related fault can affect cooling-system performance.
08
Internal engine problem
Not every overheating problem is caused by an external cooling-system component.
Internal engine problems can sometimes allow combustion pressure, coolant, or engine oil to move where it should not.
Overheating alone is not enough to conclude that the engine has a failed head gasket or another major internal failure.
WHEN IT OVERHEATS
What the driving conditions can tell you
Overheats while idling but cools while driving
If engine temperature rises while sitting still or moving slowly but improves once the vehicle starts moving, radiator airflow should be considered.
At road speed, outside air naturally moves through the radiator. At idle, the vehicle depends much more heavily on its cooling fan.
A fan problem is one possible cause, but low coolant, circulation problems, radiator restrictions, and other faults can produce similar symptoms.
Overheats while driving
Overheating while driving can be caused by low coolant, coolant loss, restricted circulation, thermostat problems, water-pump problems, radiator restrictions, or other cooling-system faults.
Note whether the overheating happens during highway driving, acceleration, stop-and-go traffic, or only after the engine has been running for a certain amount of time.
Overheating even though coolant is present
Having coolant in the reservoir does not prove that the cooling system is operating correctly.
The engine can still overheat because of thermostat problems, inadequate circulation, fan failure, radiator restriction, trapped air, pressure problems, or another fault.
Vehicle keeps losing coolant
If coolant needs to be added repeatedly, the cooling system should be inspected to determine why it is losing coolant.
Some leaks are obvious, while others only become visible once the system reaches operating temperature and becomes pressurized.
COMMON COMPONENT QUESTIONS
Can these parts cause overheating?
Can a bad thermostat cause overheating?
Yes. If a thermostat remains closed or does not open sufficiently, coolant flow through the radiator can be restricted and engine temperature may rise.
But thermostat replacement should not be based only on the fact that the engine overheated.
Can a bad water pump cause overheating?
Yes. Because the water pump circulates coolant, a water-pump problem can contribute to overheating.
Some failed pumps leak externally. Others develop bearing or internal circulation problems.
Can a bad cooling fan cause overheating?
Yes. A fan that does not operate when commanded can reduce airflow through the radiator, especially when the vehicle is stopped or moving slowly.
The problem may involve the fan itself, fuse, relay, wiring, sensor, module, or another electrical component.
If electrical testing is needed, see
mobile advanced diagnostics.
A/C AND ENGINE TEMPERATURE
Why does my A/C get warm when the engine is overheating?
The engine cooling system and air-conditioning system are separate systems, but some components and operating conditions can affect both.
Inadequate airflow through the condenser and radiator can contribute to poor A/C performance and cooling-system problems, particularly while the vehicle is stopped.
Some vehicles may also reduce or disable A/C compressor operation when engine temperature becomes excessive.
If the main complaint is warm air from the vents rather than high engine temperature, see
Rexroad’s mobile A/C service.
WHAT TO DO
What should you do if your car starts overheating?
If the temperature gauge climbs into the hot range or an overheating warning appears, avoid continuing to drive unnecessarily.
If it is safe to do so, get the vehicle to a safe location and shut the engine off.
Allow the vehicle to cool before inspecting the cooling system.
DRIVING SAFETY
Can you drive a car that is overheating?
Continuing to drive an overheating vehicle can cause additional damage.
How quickly damage occurs depends on the cause and severity of the overheating, but there is no reliable safe distance to continue driving once an engine is overheating.
Severe overheating can damage cylinder heads, head gaskets, engine components, seals, and other parts.
If the temperature continues to rise, the safer approach is to stop driving and determine why the engine is overheating.
PROPER DIAGNOSIS
How is an overheating problem diagnosed?
Diagnosis starts with the symptoms and the conditions under which the vehicle overheats.
The objective is to identify why the vehicle is overheating before recommending a repair.
MOBILE SERVICE IN FRISCO
Mobile cooling system repair in Frisco, TX
Rexroad Mobile Auto Repair provides mobile cooling-system diagnosis and eligible repairs in Frisco and nearby communities.
Coolant leak diagnosis
Visible and pressure-related leaks can be inspected to determine where coolant is escaping.
Radiator hoses
Damaged, leaking, swollen, or deteriorated radiator hoses can be replaced when appropriate.
Thermostat replacement
Thermostat operation can be evaluated and the component replaced when failure is confirmed.
Cooling fan diagnosis
Fan operation and related electrical controls can be checked when overheating happens at idle or low speed.
Water pump diagnosis
Water pumps can be inspected for leaks, bearing concerns, and other signs of failure.
Overheating diagnosis
The cooling system can be evaluated as a whole to determine the actual cause before parts are replaced.
RELATED SERVICES
Cooling-system and diagnostic help
Learn more about
Rexroad’s mobile cooling system service
.
If electrical testing is needed for a cooling fan or control issue, see
mobile advanced diagnostics.
If the primary complaint is warm air from the vents rather than engine temperature, see
mobile auto A/C service.
You can also
view all mobile auto repair services
or learn more about
mobile mechanic service in Frisco, TX.
CAR OVERHEATING?
Tell me exactly what the vehicle is doing.
Send me the year, make, model, temperature-gauge behavior, warning lights, visible coolant leaks, when the overheating occurs, and your vehicle location.
Call or text
(469) 469-4521
or submit a service request online.
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