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! Find a retailer

Why is my engine coolant low?

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 coolant 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. 

Coolant leak symptoms

The following can be signs of a coolant leak:

    • Pool of coolant underneath your car when you’re parked. This can look like green, pink, orange, blue or yellow puddles under your vehicle.
    • Overheating engine. Some car owners have also reported noticing the ‘Check Engine’ light displaying on the dashboard before identifying a coolant leak. Low coolant levels affect engine temperature, causing the sensor to trigger a false reading and light up the ‘Check Engine’ or coolant warning sign.
    • A sweet “burn off” smell can suggest that there is a coolant leak.
    • Low coolant levels which require replacing the coolant more often than usual.
A 'check engine' light glows on a car dashboard.
A ‘check engine’ light on a dashboard.

What causes a coolant leak?

Poor vehicle maintenance, as well as general wear and tear, contributes to the majority of coolant leaks. Some of the most common reasons behind an external coolant leak are included below:

    • Radiator hoses: The rubber hoses may degrade over time. Common signs of damage to these include swelling, cracks, unusual softness or holes, which are the most likely cause of an external coolant leak.
    • Radiator cap: A secure radiator cap maintains system pressure, ensuring coolant circulation to cool the engine, while a loose or leaking cap reduces pressure and hinders cooling.

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. The most common reason behind an internal coolant leak is head gasket problems.

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 to fix a coolant leak

Depending on the cause of the coolant leak, the fix could be fairly simple and cost effective. For an external coolant leak, the radiator hose may need replacing, or you could simply just need to use a radiator stop leak

If your coolant leak is internal and caused by something such as a head gasket issue, it’s likely that you’ll need to take the car to a mechanic for repair.

Despite the issue, all coolant leaks should be further investigated and repaired to avoid risking further engine problems.

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

Engine coolant leaks can be straightforward to fix, but costs can vary significantly. Repairs typically range from $70 to $400, depending on the vehicle’s make, model, age, and type.

If extensive work is needed, such as removing and repairing the radiator or head gasket, costs could exceed $1,500.

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 with K-Seal

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.

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