The cooling system on your vehicle is a vital part of your engine’s operation and prevents damage due to overheating. This is accomplished by circulating coolant throughout the engine's water channels to absorb heat, then releasing hot coolant to the radiator to reduce its temperature before it is returned to the engine. With the high demand placed on the cooling system, parts of the system may fail over time and cause a variety of symptoms. Read on to learn more about the parts of the cooling system, their responsibilities, and symptoms of cooling system problems.
What is a Cooling System?
If your vehicle is going to keep running strong, it’s essential to keep your cooling system healthy. The cooling system is the temperature regulator for the engine, and components like your radiator, radiator hoses, and water pump use coolant to keep the engine running at a safe operating temperature by absorbing and dissipating heat. Your cooling system also plays a role in heating your vehicle’s interior, as your blower motor moves air that’s been warmed by coolant from the fins of the heater core through your vents. A properly maintained cooling system will help your vehicle run at full efficiency and prevent engine overheating, which can result in engine damage or head gasket failure.
Overheating
Overheating is the most common symptom of cooling system failure. Possible causes include water pump failure, cooling fan malfunctions, a sticking or failing thermostat, belt wear or damage, restricted air flow through the radiator, and low coolant levels. In most of these cases, you will see a temperature light that indicates overheating, your temperature gauge climbing, and possibly steam from under the hood. Your vehicle may also be equipped with a sensor that triggers a low coolant light on your dash if your coolant level is low. In any case, coolant level and cooling system inspection should always be part of your routine maintenance checklist, especially if you’ve noticed a leak. You can learn more about what causes a vehicle to overheat in our How-To Hub.
Coolant Leaks
Antifreeze or coolant puddles are the most common indicator of a coolant leak, but some leaks can be difficult to find or properly diagnose. Checking hoses for signs of cracks or damage, or tracing leaks from below the vehicle, is often the easiest way to narrow down the location of a leak. Low coolant levels should be topped off, and the leak should be investigated and repaired as soon as possible to limit the risk of overheating. When filling or topping off your cooling system with coolant, be sure to use the type of coolant specified for your vehicle. If you use concentrated coolant instead of a pre-mixed 50/50 formula, you must also use distilled water in equal proportion to the coolant for the proper coolant ratio.
Heater Blows Cold Air
This issue is not as common, but can be easily identified if your temperature gauge reads low or if your heater isn’t blowing warm air. This is most commonly caused by low coolant levels or thermostat failure. The engine may be slow to reach operating temperature or may never heat up as much as it should, which can cause performance problems and prevent your heater from blowing warm air.
Temperature Fluctuation
If your vehicle’s temperature is rising and falling unpredictably during operation, it’s possible that your coolant level is low or that your thermostat is behaving erratically. This can cause your vehicle’s temperature to rise slowly after startup, fail to reach operating temperature, or rise to an unsafe level. When filling your cooling system, be sure to use the coolant specified for your vehicle. If you use concentrated coolant instead of a pre-mixed 50/50 formula, use distilled water in equal proportion to the coolant for the proper ratio.
The cooling system works hard to keep your vehicle’s cabin, engine, and other components at the right temperature. This system is made up of several parts, including the water pump, radiator, coolant reservoir, thermostat, belts, and the cooling fan. With time, these parts can wear out or fail due to age and constant use, or may be damaged if the engine overheats. It is important to follow your manufacturer’s inspection and maintenance intervals to keep your vehicle’s cooling system performing its best.
Your vehicle’s water pump moves coolant throughout the engine to keep it from overheating. Water pumps include an impeller located in the engine's water channel that is driven by a pulley powered by the engine’s timing belt or serpentine belt. If the water pump fails, you may hear squeaking from the water pump pulley, or you might notice coolant leaks or steam coming from under the hood, and the engine may overheat.
Your vehicle’s radiator acts as a heat exchanger, transporting warm antifreeze through a series of tubes surrounded by metal fins that use air from the grille or cooling fan to reduce the heat of the coolant, keeping your engine from overheating. With both upper and lower radiator hoses working constantly, the hoses can crack, split, or fail due to heat, age, and use. The radiator may also clog internally or develop leaks, which may cause visible coolant leaks or steam coming from under the hood.
Radiator Hoses
The radiator hoses on your vehicle transport coolant to and from the engine and radiator, allowing it to circulate and be cooled by the radiator and cooling fan. Most vehicles have both an upper and lower radiator hose, though modern vehicles may have a more complex system of radiator hoses designed to circulate coolant properly. Upper radiator hoses are typically connected to the thermostat housing or water outlet, and allow hot coolant into the radiator when the thermostat is open. Lower radiator hoses connect the radiator to the water pump or water inlet to draw coolant back into the engine from the radiator after it has been cooled. Radiator hoses can develop leaks over time due to damage or wear, and may dry out and become brittle or spongy over time. Regularly inspecting radiator hoses is a simple DIY task, as visible inspection and squeezing the hose is often enough to determine if it is still in usable condition. If you notice leaks near your radiator hoses, it may be a good idea to inspect the areas around the hoses as well for the source of the leak. Leaking radiator hoses should be replaced as soon as possible to prevent low coolant levels, overheating, or bursting, which can quickly render your vehicle inoperable. If you want to learn more about the symptoms of bad radiator hoses, visit our How-To Hub for additional resources.
There are multiple belts that power the accessory drive on your engine, as well as your vehicle’s water pump, which pressurizes the cooling system and keeps coolant circulating. Your vehicle’s serpentine or V-belts, as well as the tensioner and idler pulleys, play crucial roles in operating your car, truck, or SUV’s power steering pump, A/C compressor, and alternator, but cannot be overlooked if you suspect cooling system problems. Failing belts can cause costly or permanent engine damage, so it is important to inspect the belts for signs of failure or wear and replace them if you notice squeaking or squealing sounds from under the hood, cracked or brittle belts, or if the belt is slipping. You can learn more about how to inspect and replace your engine belts with our helpful article.
The thermostat helps control the flow of coolant from your vehicle’s engine to the radiator, and opens and closes depending on the temperature of the coolant inside the engine. If your thermostat is stuck open, your engine may fail to heat up to its normal operating temperature. If the thermostat sticks closed or behaves erratically, the engine may overheat or you may notice decreased engine performance. This can cause internal engine or head gasket damage due to a lack of coolant circulation.
Your vehicle’s coolant recovery tank or coolant reservoir stores hot coolant after it has been released by the radiator cap due to expansion to prevent overflow, and returns it to the radiator once the system has cooled down. You may have a coolant reservoir leak if you notice cracks or damage to the tank, or if you often have to top off the coolant level, if there are visible coolant leaks near the tank.
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Do It Right: Learn how to properly flush and fill your antifreeze with this this How-to Video. |
The cooling fan moves air throughout the radiator when your vehicle is moving slowly or is at a stop to reduce the temperature of the coolant passing through the radiator. Cooling fans may be mechanical or electric, and are often temperature-controlled to turn on and off when needed. The cooling fan helps dissipate heat from the coolant in the radiator before it is returned to the engine. If this component fails, it can affect the cooling system and A/C system performance. Inspect the cooling fan if it is running constantly, if it fails to activate when the engine is at operating temperature, or if the engine is overheating.
Heater Core
Your vehicle’s heater core provides warm air for your cabin when you turn on your heater. Warm coolant from the engine passes through the heater core, and the blower motor moves air over its heated fins and through the vents. As a heater core ages, it can begin to leak or become clogged. If you’ve noticed your heater not warming up, a sweet smell from your vents when the heater is running, coolant on the floor of your vehicle, or your windows not defrosting, these could be signs of a leaking or clogged heater core. A clogged heater core may in some cases be fixed with a cooling system flush, but a leaking heater core will need to be replaced.
Heater Hoses
Heater hoses connect the heater core to the engine and the rest of the cooling system to move warm coolant from your water pump through your heater core and back to the engine. The heater hoses on your vehicle can dry out, crack, become soft, or split over time, and their connecting fittings can also wear out and no longer form a complete seal. When the heater hoses or fittings fail, you could see leaks at the back of your engine compartment, near your engine where the hoses connect to the water pump, or in extreme cases, you might notice coolant inside your cabin on the floorboard. If you notice a leak or if your cabin isn't getting warm, check the condition of your heater hoses and replace them if they are leaking or noticeably worn out.
Heater Control Valves
Some vehicles are equipped with heater control valves that open and close to manage the flow of coolant through the heater core. In some cooling systems, the heater control valve will stay closed most of the time, stopping the flow of coolant until the heater is activated. In other cases, the valve will remain open, allowing the flow of coolant and only closing when the temperature control is moved to the coldest setting. Heater control valves can be operated electronically, or they may be actuated by cables or engine vacuum. A faulty heater valve can keep your vehicle’s heater from working if it is stuck in the closed position, cause your cabin to always be too warm if stuck in the open position, or develop coolant leaks over time that will require replacement.
Blower Motors & Blower Motor Resistors
Your blower motor moves air through the heating and A/C system of your vehicle, sending air to the cabin via the vents. Depending on the position of the vent and blend door, air may come from below the dash or out of the defroster or dash vents, and may pass over the A/C evaporator for cool air or the heater core for hot air. If you aren’t getting airflow from the vents, it’s possible that you have a bad blower motor or blower motor resistor, a blown fuse, or a faulty connector. A fan stuck on one speed is typically caused by a malfunctioning blower motor resistor, but a lack of any airflow, noise when the blower motor is activated, and other symptoms may point to a worn out or damaged blower motor. In most vehicles, the blower motor is located under the glove box or dash above the passenger side floorboard. Always check the blower motor or climate control fuse or relays first, as these are the easiest items to replace to get your blower motor working again. If there aren’t any signs of damage to the fuse or relay, check the blower motor resistor and plug for melting or other damage. If these items seem to be in good repair, the blower motor itself may need to be replaced. If you need to replace your blower motor, watch our How-To video to learn more.
Regular maintenance, including checking coolant levels, flushing and filling the radiator, changing belts, and replacing hoses when needed can help you maintain the cooling system’s operation and keep your vehicle performing at its best. If you see coolant leaks, steam from under the hood, notice your vehicle is overheating, if the heater isn’t working as it should, or if you hear squealing or grinding sounds from the engine, it may be a good time to inspect your cooling system components. If you are in need of replacement cooling system parts, O’Reilly Auto Parts carries the right parts, tools, equipment, and cooling system accessories to help you make a complete repair and keep your vehicle running cool for many more miles to come.
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