What causes coolant to leak from your car?

Coolant leaks are common in vehicles of all shapes and sizes. Find out what causes coolant to leak, and how to fix the issue permanently with K-Seal!

Why does my engine keep losing coolant?

Sometimes your vehicle will lose engine coolant, as if by magic. However, the reason your car’s losing coolant is far from magical: it’s almost always thanks to a coolant leak.

There are three main causes for coolant leaks:

  1. External leaks
  2. Radiator cap leaks
  3. Internal leaks.

How much coolant loss is normal?

Providing that the engine is running well, with no leakages or damage, you can expect a coolant loss of 0.25% every four to six months. This means a loss of two to three ounces a year is completely normal. However, anything over that is the sign of a more significant coolant leak and you should investigate the problem further.

If you do discover a larger coolant leak, use K-Seal or K-Seal Ultimate to seal the leak fast. 

Common signs of a coolant leak

The easiest way to identify if you have a coolant leak is by checking underneath the engine for any puddles that are forming when you’re parked.

If you notice one, keep an eye on your coolant levels as you drive. If they start dropping faster than normal, then you’ve probably got a coolant leak on your hands!

Can coolant leak cause check engine light to show?

Some car owners have also reported noticing the ‘Check Engine’ light displaying on the dashboard before identifying a coolant leak. 

A 'check engine' light glows on a car dashboard.
A ‘check engine’ light on a dashboard.

This is because, when the coolant level is too low it affects the temperature level in the engine. If the temperature sensor in the engine judges the coolant to be too low to effectively protect the engine, it will provide a false reading, and trigger the ‘Check Engine’ or engine coolant sign to light up.

How to identify external coolant leaks

Check your radiator hoses, the radiator and coolant reservoir or tank. Radiator hoses are common culprits, as the rubber hoses may degrade over time. Common signs of damage to these include swelling, cracks, unusual softness or holes.

Generally, small holes in your radiator hoses or loose connections between hoses and the cooling system are the most likely cause of an external coolant leak.

How to fix an external coolant leak

This should be fairly simple, and cost effective. If you notice any of the common signs your radiator hoses are damaged, replace them immediately.

However, external leaks can also occur if your radiator is damaged or leaking. And if that’s the case, you need to get hold of a radiator stop leak or you could be risking further engine problems.

A radiator cap leak could cause you to lose coolant

A secure radiator cap will seal the radiator system and maintain its pressure. This is vital to ensuring that the mix of coolant and water designed can move through the system to cool the engine as needed.

If the radiator cap is loose or leaking, this reduces the pressure and makes it harder for coolant to keep the engine from overheating.

A close up of a car radiator cap.
A car radiator cap.

You can diagnose this yourself by consulting your car owner’s manual and checking the radiator cap to make sure it has the right pressure. You can also take it to a mechanic for a service to be sure.

What causes coolant to leak internally?

If you’ve checked your car for external and radiator cap leaks but found nothing, check your coolant levels.

If your coolant levels are still going down despite there being no evidence of a leak, you may have a bigger problem: an internal coolant leak.

A leaky or blown head gasket is often what causes coolant to leak internally. Forming a seal around the combustion chamber, a head gasket is critical to preventing engine coolant and oil from contaminating that chamber and causing serious, costly damage to your engine.

Fortunately, there are a number of common symptoms of a leaky head gasket you can watch out for to prevent this happening.

How much does it cost to fix a coolant leak in a car?

The cost of fixing an internal coolant leak in a car can be around $100 if you take it to a mechanic. But the longer you leave it, the more damage can be done to your engine, and the more repairs will cost you.

Can you drive a car with a coolant leak?

We’d strongly recommend against it. Keep driving despite the warning signs, and you’ll only do more damage to your engine. And that means more costly repairs!

If you do need to drive to a mechanic or to pick up a bottle of coolant leak repair, that’s completely understandable. Just make sure you keep an eye on your coolant levels.

A dashboard shows a coolant warning message: 'Coolant level low - add coolant'.
Watch out for low coolant levels in your engine.

If your coolant levels start dropping even more quickly, then you have a serious internal coolant leak that needs fixing, fast. 

How to fix a coolant leak, permanently

Catch a coolant leak early and you can avoid costly repairs by grabbing a bottle of K-Seal Coolant Leak Repair from your local supplier.

Trusted by millions of customers and mechanics worldwide, its scientifically proven formula seeks out any holes and cracks and holes in your engine, sealing them permanently. Follow the simple instructions on the label and your coolant leak will be repaired in minutes—getting you back on the road, fast.

Find your nearest K-Seal supplier

Fix coolant leaks fast with K-Seal

Expert Advice

Head Gasket Failure? Cracked Head or Block?
Leaking Radiator?

Expert Advice

Where to buy K-Seal

Have any of these symptoms? K-Seal could save you thousands on a workshop repair. Search for a stockist today!

Where to buy