Car Talk

Cause for Coolant Leak: Where is the Fluid Coming From?

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The engine maintains its optimal operation temperature through a straightforward method. First, the liquid flows over the engine block, absorbing the heat generated. Then, it returns through the cooler, releasing and distributing the collected heat, ready to be recirculated to continue the process. There are a couple of reasons why your vehicle’s coolant level might be low, and you cannot always blame the leak. For example, you might just have changed the coolant, and the airlocks in the system are now cleared, and the coolant needs to be topped up to the correct level.

However, if you haven’t renewed the coolant, the culprit might be the leak either from the radiator or elsewhere. The coolant is present in a sealed system, so usually, the coolant level does not change if it is checked when the engine is cold. When the engine is warm, its level rises as water expands when it’s hot and falls back to the mean level as it cools down.

Causes for Engine Losing Coolant with No Leak, No Overheating 

Some of the common reasons for an engine to lose coolant with no visible leak signs include 

  • Internal leakage of the head gasket into the combustion chambers
  • Worn turbocharger seal leaking into the exhaust system
  • Pressurized coolant seeps out of the radiator cap as steam
  • The coolant leak is too small to notice and might be evaporating

Coolant Leaks: Internal and External

There are two types of coolant leaks.

External If you notice a leak on a hose, engine block, or radiator and see coolant leaking from the bottom of the car, it is an external leak.

Internal – if you cannot see any puddles beneath the vehicle, but your coolant is dripping, it’s probably an internal leak, which means your coolant is leaking into the engine.

What Causes External Car Coolant Leaks?

Here are some of the possible causes for an external car leaking coolant

  • Coolant Pump Seal Leaking

The coolant pump has a seal that prevents it from leaking past the bearing. If the seal is not functioning correctly, the coolant can seep out where the coolant pump pulley shaft enters the pump housing. If the pump gasket fails, a leak can occur between the engine block and the pump. 

  • Radiator Leak

Stone chips and age can be the radiator’s worst enemy. The issue is that if the radiator leak is small, the coolant can evaporate even before pooling on the floor, not letting you find its actual location. So, if you cannot find the apparent radiator leak, look for small puffs of steam missing from the radio when your car is hot. You might also be able to smell the coolant in the engine bay. 

  • Split Coolant Hose

Even the tiniest pinprick in a hose can cause a coolant leak. Sometimes, this leak can only be observed when the engine is hot. When a car is just ticking, there isn’t enough pressure in the system for the leak to be apparent. However, you can see coolant leak symptoms around the leak area as it leaves behind a colored residue. If you take a good look around the engine, you will be able to see more significant splits. The splits can also be caused by metal clips that secure hoses.

  • Heater Matrix Leaking

Your vehicle’s coolant keeps you warm in the winter through the heater mix. The heater matrix is mounted behind the dashboard and occasionally leaks. Because of its location, finding a leak can be difficult. However, if you have recently noticed condensation and coolant loss on the inside of the window, the matrix might be at fault.

Causes for Internal Car Coolant Leak

If the coolant level drops without any external leak, then the coolant leaks from inside into the engine. If your vehicle has been overheated recently, it can cause the head gasket to fail. If that’s the case, it can cause coolant to leak into the combustion chamber.

Signs for Internal Gasket Failure

Common signs of internal gasket failure include

  • Coolant mixed with the oil
  • Overheating vehicle
  • White smoke comes out of the exhaust, even when the engine runs optimally.
  • Coolant bubbling
  • Dripping water from the exhaust manifold
  • Lumpy running and poor starting
  • Air Pockets in the Cooling System.

The head gasket leak can be analyzed by testing for hydrocarbons in the coolant system. The gasket is blown if there is a presence of hydrocarbons.

Unable to Find Coolant Leak? Here is How You Can Stop Your Car from Losing Antifreeze

Not sure where does antifreeze go? Here is how you can find and fix the issue’s source. 

  • Check Coolant Reservoir Levels 

 If you notice any symptoms of coolant leak with no visible symptoms of coolant loss or no visible leaks, then it is preferable to check the reservoir before driving any further. If you cannot find any visible leaks, you should not start the engine again until you can add more. 

  • Find the Source of the Leak 

To know where the leak is coming from, the best option is a UV detection eye that is poured directly into the radiator. As the dye circulates through the cooling system, leaks will become visible under black light. 

For internal leaks, UV dye is ineffective, requiring you to do a leak-down test. It consists of injecting compressed air into the cylinder and gauging the amount that leaks out. 

  • Fix the Leak or Consult a Professional 

If a bad radiator cap is the cause of a coolant leak or a collapsed hose, you can buy the parts from any auto shop and replace them yourself. However, if the head gasket is cracked or faulty or you can’t find the coolant leak, you may want to consult a professional. Depending upon the size of the leak and its location, you might also want to consider using a radiator stop-leak product; they are pictured in the radiator, and the seal leaks in aluminum, metal, and plastic. 

However, the majority of manufacturers suggest you avoid using these products as they might cause engine issues and even long-lasting damage to your vehicle. 


Experiencing low coolant levels without any visible signs of leaks can be exhausting. However, it is essential to address this issue to prevent engine damage from overheating. You can start by checking visible signs of leaks, and if you cannot find any, consider the possibility of cap issues or internal leaks. 

Suppose you are unable to identify the problem yourself. In that case, you may seek assistance from a professional who can identify the cause and make necessary repairs to ensure your cooling system is in optimum condition. Regular inspection and maintenance are essential to ensure your vehicle’s cooling system is functioning optimally and protect your engine from potential damage. 

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