The engine cooling system plays a very important role in the efficient operation of the engine. Vehicles can either be liquid-cooled or air-cooled. Though, it is uncommon to see a vehicle manufactured with an air-cooling system.
Note that this article is focused on liquid cooling systems. The liquid cooling system of a vehicle consists of various components.
It includes; the radiator, which is mostly an aluminum radiator, the thermostat, hoses, water pump or coolant pump, a radiator cooling fan, heater core, bypass system, head gaskets, and a few other components.
So, we will concentrate on the signs of no coolant in the radiator but the reservoir tank is full, the causes of lack of coolant in the radiator when there is a full reservoir tank, and the ways to fix this issue.
The liquid cooling systems function by transporting the coolant through a passage in the engine blocks and heads. The coolant picks up heat as it passes through the engine. The coolant is heated and then flows to the radiator through a rubber hose.
The heated coolant moves through the thin tubes in the radiator, and it is cooled by the airflow toward the engine compartment from the car’s grill. Immediately the liquid is cooled, it flows back to the engine to reduce its temperature.
Understanding the Coolant Reservoir and Radiator Functions
Unraveling the mystery of an empty coolant reservoir while the radiator remains full requires a deep understanding of the functions performed by these two critical components in your car’s cooling system.
In this section, we will provide an in-depth explanation of the coolant reservoir and radiator functions, shedding light on their roles in maintaining optimal engine temperature.
By comprehending these functions, we can gain valuable insights into the causes behind the observed issue.
In a vehicle’s cooling system, the coolant reservoir serves an essential role. Acting as a storage tank, it holds excess coolant and aids in maintaining consistent coolant levels in the system.
When the engine heats up, coolant expands and flows into the reservoir, relieving pressure in the cooling system. Conversely, as the engine cools down, the coolant from the reservoir is drawn back into the radiator, ensuring a constant supply of coolant.
The radiator, on the other hand, is responsible for dissipating the excess heat generated by the engine. It directs the flow of coolant, facilitating heat transfer and preventing engine overheating.
As coolant passes through the radiator’s network of tubes, fins, and cooling fans, it undergoes a cooling process, allowing the engine to maintain a safe operating temperature.
| Coolant reservoir function | Radiator function |
|---|---|
| Storage tank for excess coolant | Dissipates excess heat from the engine |
| Maintains consistent coolant levels | Facilitates heat transfer |
| Relieves pressure in the cooling system | Prevents engine overheating |
By understanding the functions of the coolant reservoir and radiator, we can discern the potential causes behind an empty coolant reservoir while the radiator remains full.
In the next sections, we will explore these causes in greater detail, equipping you with the knowledge to address and resolve this issue effectively.
Signs of No Coolant in the Radiator, but the Reservoir is Full
The common reason for no coolant in radiator but the reservoir is full is a blown head gasket.
If a head gasket blows, the combustion gases from the cylinders will leak into the cooling system and push the coolant into the reservoir. Once the reservoir gets filled, the rest will waste through the overflow outlet.
However, other factors can cause issues in the cooling system. It could be as a result of lousy thermostat, bad radiator, and other related cooling system parts. Let’s look at these possible causes.
#1. The engine will begin to overheat.
It is a very common sign that reflects that something is wrong with the cooling system. It can be due to a faulty radiator or a bad thermostat or even other related issues.
This problem can drastically reduce the functionality of the vehicle due to engine poor performance. Overheating the engine will produce smoke, and it might lead to a sudden breakdown of the vehicle.
#2. The heater may be Malfunctioning.
When the heater in the car does not function, it is a sign that there might not be coolant in the radiator. The heater depends on the hot fluid that flows through the core. As the hot fluid flows, it releases hot air that blows into the car.
#3. Leakage of coolant.
Another common sign that shows no coolant in the radiator is coolant leaks from the car. It can be dropping from the radiator or the hoses.
The radiator’s coolant level becomes low if it has been punctured. This will cause the engine to overheat because no coolant absorbs its temperature.
#4. Discoloration of coolant.
The lack or shortage of coolant in the radiator can cause the coolant to change in color. The engine coolant is mostly green, yellow, or pink. This color can change to a thick brown-like color if there is contamination. This can obstruct the flow, and it can also clog the radiator.
#5. Engine check light.
If the radiator has no coolant, there will be a high increase in the engine’s temperature. This will turn the engine check light on so that the driver will know that there is an issue. You must track and fix the root cause to prevent a major engine damage.
#6. Persistent odor.
You might constantly perceive a sweet smell when you are around or inside your car. The coolant’s smell is noted as a sweet smell.
Therefore, perceiving this type of smell can signify that there might be a leakage of coolant under your car. It’s best to investigate further to be sure of the cause.
#7. Smoke from the engine.
If there is a release of white smoke from the exhaust of your vehicle. It may mean that the radiator’s coolant level is very low and should be refilled. However, if you see the release of white smoke from the exhaust, the damage is already done.
So, don’t wait until you see this sign before taking necessary actions.
#8. A damaged radiator cap.
The radiator cap is responsible for making sure the coolant do not escape and keeping it at the right pressure. If you have a damaged radiator cap, it will cause coolant leak, leading to a low coolant level.
A damaged radiator cap can also break the hoses by building high pressure in them, creating another channel for the escape of coolant. A faulty radiator cap can cause the coolant reservoir to overflow and overheat the vehicle’s engine system.
#9. Torn radiator hose.
The radiator hoses are always transporting hot fluid. As a result, the hoses will eventually wear out and tear. Especially if your vehicle is used for daily long trips, the hoses will likely wear out fast. The hoses might even explode, causing coolant to flow out from it easily.
#10. Faulty head gasket.
A damaged head gasket will turn the engine check light on. The head gasket is responsible for sealing the space between the cylinder and the engine block.
It also facilitates the smooth flow of oil and coolant. If the head gasket blows, it will allow coolant to enter and burn in the combustion chambers.
#11. Damaged intake manifold gasket.
This component is located on top of the engine. The intake manifold provides fuel and airstream to the combustion chamber.
A gasket is found inside the intake manifold, where it merges with the engine. This gasket can get damaged, leading to leakage of coolant in your vehicle.
#12. Bad radiator or water pump.
The radiator helps to cool the heated coolant as it passes through its metal tubes, preventing engine overheat.
The water pump circulates coolant to other engine parts. It is responsible for the easy flow of coolant through the radiator and engine block. If the component becomes faulty, it’ll cause a severe leak.
Diagnosing The Issue
Experiencing no coolant in the radiator but a full reservoir tank can be confusing. Proper diagnosis is essential to identify the root cause. Below are some effective methods to diagnose this issue.
#1. Visual Inspection.
Start by performing a visual inspection. Check for any visible leaks around the radiator and hoses. Look for signs of dried coolant or wet spots. Examine the radiator cap for any signs of damage or wear. A faulty cap can cause coolant to overflow into the reservoir.
#2. Pressure Testing.
Next, perform a pressure test on the cooling system. A pressure tester will help identify leaks that are not visible.
Attach the tester to the radiator and pump it to the specified pressure. Observe the gauge for any drop in pressure. A drop indicates a leak in the system.
#3. Coolant Dye Test.
For more precise detection, use a coolant dye test. Add the dye to the coolant system. Run the engine for a short period to circulate the dye.
Use a UV light to inspect the system. The dye will glow under the light, revealing even the smallest leaks. This test is highly effective for finding hidden leaks.
Fixing the No Coolant in Radiator issue
When facing the situation of no coolant in the radiator but a full reservoir tank, it is important to take appropriate actions to diagnose and resolve the issue. Here are some recommended steps to follow:
#1. Cool Down the Engine.
First and foremost, allow the engine to cool down before inspecting the cooling system. Working on a hot engine can be dangerous and may result in burns.
#2. Check for Coolant Leakage.
Inspect the radiator, hoses, and other components of the cooling system for any signs of coolant leakage. Look for visible coolant stains, wet spots, or puddles under the vehicle.
If leakage is detected, it is crucial to identify and address the source promptly. Common areas of leakage include radiator seams, hose connections, and water pump seals.
#3. Inspect the Radiator Cap.
Examine the radiator cap for any signs of damage or wear. A faulty radiator cap can cause coolant to bypass the radiator and accumulate in the reservoir tank.
If the cap shows signs of deterioration or does not seal properly, it is recommended to replace it with a new one.
#4. Check for Air Pockets.
Air pockets trapped within the cooling system can disrupt coolant flow to the radiator.
To remove air pockets, locate the coolant bleeder valve or screw on the cooling system (if present) and carefully release any trapped air.
Consult the vehicle’s manual for specific instructions on bleeding the cooling system.
#5. Verify Coolant Levels.
After the engine has cooled down, verify the coolant levels in both the radiator and the reservoir tank. If the radiator is empty or significantly low on coolant while the reservoir tank is full, it may indicate an issue with coolant circulation.
In such cases, it is recommended to consult a professional mechanic for a thorough inspection and diagnosis.
#6. Perform a Flush and Refill.
If necessary, consider performing a coolant flush to remove any contaminants or buildup within the cooling system.
Flushing the system involves draining the old coolant and replacing it with fresh coolant. Follow the vehicle manufacturer’s guidelines and use the recommended coolant type and mixture ratio.
It is essential to properly dispose of the old coolant according to local regulations.
#7. Regular Maintenance.
To prevent future issues with coolant distribution, follow the vehicle manufacturer’s recommended maintenance schedule.
This includes regular coolant checks, inspections for leaks, and preventive measures to ensure the cooling system operates optimally.
Proper Maintenance for a Healthy Cooling System
Regular maintenance is crucial for keeping your car’s cooling system in optimal condition, preventing issues such as an empty coolant reservoir.
By following the right maintenance practices, you can ensure that your vehicle’s cooling system operates efficiently and effectively. Here are some practical tips and guidelines:
#1. Check for Leaks.
Inspect your cooling system regularly for any signs of leaks. Look for coolant puddles under your car, particularly around the radiator, hoses, and water pump. If you notice any leaks, address them promptly to prevent coolant loss and potential engine overheating.
#2. Monitor Coolant Levels.
Keep an eye on your coolant levels by regularly checking the coolant reservoir. Ensure that the coolant is at the proper level, as indicated by the markings on the reservoir.
If you notice the coolant level dropping consistently, it could be a sign of a leak or another underlying issue. Monitor the levels closely and address any abnormalities promptly.
#3. Flush and Replace Coolant.
Periodically flushing and replacing the coolant in your car’s cooling system is crucial for maintaining its effectiveness.
Over time, coolant can become contaminated with debris, rust, or other impurities that can hinder its performance. Refer to your vehicle’s manual for the recommended coolant flush and replacement interval.
#4. Follow Manufacturer Guidelines.
Always adhere to the manufacturer’s guidelines for cooling system maintenance. This includes using the recommended coolant type, following the correct coolant-to-water ratio, and adhering to the recommended service intervals.
By following these guidelines, you can help prevent issues that can lead to an empty coolant reservoir.
#5. Inspect Radiator and Hoses.
Regularly inspect the radiator and hoses for any signs of damage, such as cracks, leaks, or bulges.
These components are essential for the proper circulation of coolant within the cooling system. Any damage should be addressed promptly to prevent coolant loss and system inefficiencies.
#6. Keep the Cooling System Clean.
Maintain a clean cooling system by periodically flushing out debris or sediment that may accumulate.
You can use a cooling system cleaner to remove any buildup that can hinder the performance of the radiator or other components. A clean cooling system will help prevent clogs and ensure proper coolant flow.
#7. Seek Professional Maintenance.
While regular maintenance can go a long way in preventing an empty coolant reservoir, it’s also essential to seek professional assistance when needed.
A professional mechanic can perform a thorough inspection of your cooling system, identify any hidden issues, and provide expert guidance on maintenance and repairs.
By following these maintenance tips and guidelines, you can maintain a healthy cooling system, prevent an empty coolant reservoir, and ensure the smooth operation of your vehicle.
Remember, a well-maintained cooling system is essential for keeping your engine cool and avoiding costly repairs.
FAQs.
Q: What does it mean if your coolant reservoir is full, but the radiator is empty?
The common reason the coolant reservoir is full but the radiator is empty is an indication of a coolant leak from the car.
It could be a result of bad thermostat housing, bad radiator, or other related parts. Other possible causes are coolant leaks, blown head gaskets, and bad water pumps.
Q: Why is coolant not returning from the overflow tank?
The common reason coolant is not returning to the overflow tank is a coolant leakage. It could be from the radiator hoses, cap, water pump, or the radiator itself.
If the radiator cap is faulty, it will allow engine coolant to escape, and this will lead to the coolant not returning to the reservoir.
Q: Does the radiator reservoir need to be full?
The radiator reservoir is an important component in the engine cooling system. It needs to reach the maximum line.
The radiator reservoir stores the excess coolant until it is needed to reduce the temperature of the engine. If the coolant in the radiator reservoir is low, it can cause the engine to overheat. So you need to check the coolant level in the reservoir frequently.
Q: Why is the coolant reservoir empty?
If the coolant reservoir is empty, you have a leak in the system. A damaged reservoir tank can cause evaporation of the coolant, which is the cause of the coolant reservoir not filling up. The drop rate in the level of coolant depends on the extent of the damage.
Q: Do you put coolant in the radiator or reservoir?
It is recommended to pour coolant directly into the reservoir when topping off the reservoir. But if you are changing the coolant, then you should pour the engine coolant through the radiator.
Final Words
The cooling system of the vehicle does not just keep the engine at a moderate temperature. It ensures the smooth operation and high efficiency of the engine. This is one of the major reasons why you must frequently check the coolant level.
This will help you to timely handle issues like no coolant in the radiator but the reservoir tank is full and also to prevent damage to the engine.