4 Causes of the Drop in Coolant Level
A sudden decrease in coolant level is one of the most common signs of a problem in the cooling system. Coolant (antifreeze) is essential for regulating engine temperature, preventing overheating, and protecting against corrosion. When levels drop unexpectedly, it signals leaks, evaporation, or internal damage. Ignoring this issue can lead to overheating, costly repairs, and even engine failure.
In this guide, we’ll explore 4 causes of decreased coolant level, explain how to diagnose them, and show how AtomEX Stop Leak Radiator can help restore system integrity. For related issues, see our Cooling System Instability blog.
Cause 1: External leaks
The most common reason for coolant loss is external leakage. Cracks in hoses, loose clamps, or damaged radiator cores allow coolant to escape. Look for puddles under the car, damp trails around joints, or a sweet smell of antifreeze. External leaks are often visible and can be sealed quickly with AtomEX Stop Leak Radiator.
Cause 2: Internal leaks
Internal leaks occur when coolant enters the combustion chamber or mixes with engine oil. Symptoms include white exhaust smoke, milky oil, or unexplained coolant loss without visible leaks. These issues often point to a failing head gasket or cracked cylinder block. While serious cases require mechanical repair, minor gasket leaks can be stabilised with stop‑leak formulations.
Cause 3: Evaporation and overheating
If the cooling system overheats, coolant may evaporate faster than normal. A faulty radiator cap or pressure imbalance can accelerate evaporation. Overheating also increases stress on hoses and joints, leading to secondary leaks. Regular inspection of the radiator cap and thermostat helps prevent this issue.
Cause 4: Corrosion and wear
Old coolant loses its protective properties, allowing rust and scale to form inside the system. Corrosion eats away at metal surfaces, creating pinholes and weak spots. This slow process leads to gradual coolant loss and reduced efficiency. Flushing the system and using AtomEX Stop Leak Radiator after coolant replacement provides long‑term protection.
How to fix decreased coolant level
AtomEX Stop Leak Radiator is designed to seal leaks in pipes, joints, and gaskets. It works in petrol, gasoline, and diesel engines, and does not harm rubber hoses, aluminium, plastic, or steel radiators. Polymers in the formula bond to leakage points, creating a durable seal.
- Warm the engine to working temperature (warm but not hot).
- Shake the can thoroughly.
- Switch off the engine and pour the product into the radiator tank.
- Restart the engine and run at tick‑over for 5–10 minutes with the interior heating turned on.
- Reapply after coolant replacement for long‑term protection.
Recommended product
Properties
- Seals leaks quickly and prevents costly repairs
- Works in all engine types and cooling systems
- Safe for gaskets, hoses, aluminium, plastic, and steel radiators
- Provides long‑term protection against rust and corrosion
For related cooling topics, see our Radiator Coolant Level blog. You can also explore oil‑related issues in our Leaking Cooling System blog.
For background on coolant systems, see this technical overview of automotive cooling systems. Understanding system components and flow helps you diagnose coolant loss more effectively.
Conclusion
A decrease in coolant level is a warning sign that should never be ignored. By understanding the 4 main causes — external leaks, internal leaks, evaporation, and corrosion — and applying AtomEX Stop Leak Radiator, you can restore system integrity, prevent overheating, and extend engine life. Combined with regular maintenance and inspections, XADO solutions ensure reliable cooling performance for years to come.