Coolant Disappearing From Reservoir With No Potential Leaks: Solving The Mystery!

There may be times when the coolant system may fail due to one reason or another. The mystery arises though when magically the coolant disappearing from reservoir is noticed with no potential signs of leakage.

Has this happened with your car too? Let’s bust the mystery for you so that you don’t scratch your heads in contemplation the next time.

What Does A Coolant Do?

Coolant is not only a liquid that comes useful in summers but winters as well. In summers, the coolant helps in deviating heat away from the car’s engine so that the running mechanical block maintains it cool. 

In winters, coolant aids in lowering the freezing point and, in turn, increasing the boiling point of the liquid, thus the name “antifreeze.”

Why Is Coolant Disappearing From Reservoir Secretively?

Low coolant levels or running with aged coolant are common problems that are observable in cars.

The curiosity arises when the coolant mysteriously disappears from the reservoir, and you don’t even witness any leaks. How is that possible?

It is a baffling situation that has more to it than you could imagine. Let’s explore and get to the root cause of the problem at hand.

coolant disappearing from reservoir
Low coolant levels or running with aged coolant are common problems in cars. (Photo: Wheels)
The real problem creeps in when the appropriate coolant levels are not maintained in the reservoir. 

Such a decrease in coolant level is evident in the form of leaks or the smell that arises when coolant exits in the form of mist. 

The real confusion arises when coolant disappearing from reservoir is witnessed without any symptoms. What could be the reason for that? Let’s find out!

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1. The Faulty Reservoir Cap

There may be times that the reservoir radiator cap may turn out to be faulty. While this may seem to be a minor issue, it can lead to dire consequences. 

In normal circumstances, the coolant gets ousted out from the reservoir overflow tube, the moment the engine starts warming up. 

This leakage is visible and may result from a bad reservoir cap. Go through maintenance tips for consequences of the overfilled coolant reservoir.

A reservoir is under pressure in normal circumstances in order to increase the coolant’s boiling point. 

In case of a faulty radiator cap, the required pressure fails to build up inside the system, leading to overheating. When this happens, the coolant is likely to simply burn-off rather and disappear.

2. Bad Head Gasket

A head gasket is a component that is sandwiched between the engine block and the cylindrical head within the combustion engine. 

The basic functionality of these gaskets is to seal the cylinders so that the coolant does not find its way into the cylinder.

why coolant disappearing from reservoir
You can solve the mystery of the problem by checking a head gasket. (Photo: keralapool)

Sometimes, though, the head gasket can turn out to be defective. Such an issue, in turn, can lead to coolant flowing into the cylinder and evaporating. 

In case the head gasket leak is a minor one; the air is likely to enter the coolant system. 

The pressure thus formed by the air causes the radiator cap to lift up. This, in turn, leads to evaporation of the coolant along with the exhaust gasses.

3. Invisible Leakage Points

When you have no idea where and why coolant disappearing from reservoir, conducting the pressure can help solve the confusion.

You would require an air pump that in turn will help you detect the leakage point when nothing is visible to the eyes.

Remove the radiator cap and attach the air pump’s tester hose to the coolant recovery tank. Now, you can start pumping in the air until the air pump’s gauge reaches the level of pressure printed on the radiator. 

Now that the system is pressurized, the leaks would be made visible through the leak points if any.

4. Leaking Turbo Seal

The majority of turbos are cooled by engine coolant. If a turbo seal fails and coolant leaks into the turbo, the coolant will escape through the exhaust.

5. Evaporation

Even though there is no visible leak on the ground, there might be a microscopic pin hole leak in one of the hose fittings. If the cooling system is not completely airtight, some coolant may slowly evaporate over time.

Sometimes there is a gradual leak that permits liquid coolant to seep out of the cooling system. When this happens, white streaks may appear at the site of the leak.

FAQs on Coolant Disappearing From Reservoir

  1. Why am I losing coolant but the engine is not overheating?

It might be a broken hose or a radiator hole. Solution: Examine your hoses to determine if any coolant is leaking. If you find coolant flowing out of the hoses, replace them.

If you discover coolant leaking from your thermostat, it is a simple remedy.

  1. How much coolant loss is considered normal?

If the engine is in good working order and there are no leaks or damage, you can expect a coolant loss of 0.25% every four to six months. This suggests that losing two to three ounces every year is perfectly normal.

  1. What happens if too much coolant is poured into the overflow?

Excess coolant is usually evacuated by an overflow pipe. If this occurs, you will most likely see a pool of coolant beneath your vehicle.

Overfilling your antifreeze tank might cause electrical damage if the overflow comes into touch with engine wiring.

  1. Will the radiator draw coolant from the reservoir?

The radiator cap enables some coolant to escape and be kept in the reservoir to relieve pressure. This extra coolant will remain in the system until the system cools sufficiently to produce negative pressure and pull the extra coolant from the reservoir back into circulation.

  1. How frequently should you replace the coolant?

When the coolant level falls below the guidance markings, it should be topped up. Manufacturers’ recommendations for draining and replacing coolant vary. 

However depending on how old your automobile is, this might be after a minimum of 30,000 miles.

  1. What tool can you use to prevent or stop coolant leak?

  • Kit for detecting UV leaks

If you find the cooling system prones to leak, you must locate the source ASAP. UV leak detection dyes are available for use in your cooling system.

Shine a dark light around the engine bay after the dyes have circulated through the cooling system. This is a quick technique to see if your cooling system is leaking outside.

  • Leak down examination

A leak down test is a good approach to find out whether your cooling system is leaking inside and where the leak is coming from.

This device connects pressurized air to each cylinder during the compression stroke and measures the amount of air that exits the combustion chamber.

Although a healthy engine will have some leakage, severe leaking on one or more cylinders indicates a mechanical issue. 

  • Radiator pressure examination

A radiator pressure test, which presses the cooling system to or slightly over its working pressure, can assist detect tiny leaks.

When doing a pressure test, take care not to overload the cooling system. A system rated for 15 psi, for example, may not be able to withstand 35 psi without damaging anything critical.

Check out this video from 1A Auto to know how to diagnose a coolant leak in details!

Wrapping Up

This is all about the causes that could lead to coolant disappearing from reservoir without any leakage. Remember never to ignore coolant leakages whether visible or not, for it may ruin a car’s engine and the drive quality.