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What Causes a Car Radiator to Crack? (Explained)

Updated: Feb 1

✔ This article has been fact checked.

A car radiator is a critical component of a vehicle's cooling system. It is responsible for preventing the engine from overheating by keeping the coolant at the right operating temperature (around 90-105°C or 195-221°F).

A cracked radiator can cause serious issues for your car and can lead to costly repairs. It's usually caused by a number of factors including physical damage from road debris or collisions, the coolant overheating, over-pressurising, or fluctuating in temperature.

In this article, we will discuss the causes of a cracked radiator, the signs to look out for, and important information to know if you suspect your radiator is cracked.

Table of Contents:

a cracked radiator

Causes of a Cracked Radiator

There are several reasons why a radiator may crack, including the following.

  • Coolant Temperature Fluctuations: Constant changes and fluctuations in coolant temperature can cause the metal of the radiator to expand and contract, leading to heat stress on the material and eventually causing the radiator to crack.

  • Rocks and Road Debris: The radiator is typically located at the front of the vehicle, making it vulnerable to damage from rocks and other debris kicked up by the wheels of other cars.

  • Accidents and Damage: Collisions and other accidents can cause damage to the radiator, leading to it cracking.

  • Radiator Fan Malfunctioning: If the radiator fan is not functioning properly, it can cause the radiator to overheat and crack.

  • Dirty Coolant: Over time, coolant can become dirty and clogged, leading to decreased cooling efficiency and potential cracking of the radiator.

  • Coolant Over Pressure: When the pressure of the coolant fluid inside the radiator exceeds the recommended levels, it can cause cracking of the metal.

Although those listed above are the most common causes of a cracked radiator, they are not the only causes.

coolant temperature gauge on a car

What Are the Signs of a Cracked Radiator?

Below are the common signs of a cracked car radiator.

  • Low Coolant Level: If you notice that the coolant level in your car is dropping, it could be a sign of a cracked radiator.

  • Sludge or Debris in the Radiator: Debris or sludge buildup in the coolant and radiator can indicate a leak in the radiator.

  • Overheating: If your car is overheating, it could be a sign that coolant is leaking from a crack in the radiator.

  • Coolant Leaking: A cracked radiator can cause coolant to leak onto the floor, which can be noticed by a puddle of fluid underneath your car.

coolant leaking from under a car

Additionally, you may notice that the temperature gauge in your car is consistently reading higher than normal or that the radiator is leaking coolant. The coolant temperature gauge can be a good indicator, if it is reading higher than normal it could be a sign of a cracked radiator.

You may also notice that the engine is overheating frequently or that the heater in your car is not running as well as it should. This can be caused by a lack of coolant in the system due to a leak in the radiator from the crack.

You may also notice that the coolant is discoloured or that there is a sweet smell coming from the engine. This can be caused by coolant mixing with oil, which can be an indication of a cracked radiator.

In some cases, you may also notice that the engine is making strange noises such as knocking, ticking, or hissing. This can be caused by the engine overheating, which is a symptom of a crack in the radiator.

Another sign is the presence of bubbles in the coolant. When the radiator is cracked, the coolant can escape through the crack and mix with the air, creating bubbles. This can be noticed by looking at the coolant reservoir or by looking at the coolant in the radiator.

Is It a Cracked Radiator or a Head Gasket Issue?

It can be difficult to determine whether a radiator is cracked or if the issue is with the head gasket. A professional mechanic can diagnose the problem by performing a pressure test on the cooling system.

One way to know for sure if the issue is a head gasket issue or caused by a cracked radiator is to check the engine oil filler cap. If it has a milky and frothy appearance, it's likely to be a blown head gasket.

damaged head gasket

How Long Can You Drive With a Crack in the Radiator?

Driving with a cracked radiator can be dangerous and should be avoided. If the radiator has a crack, it can rapidly cause the engine to overheat, leading to damage to the engine and other components.

It is best to have a damaged car radiator repaired or replaced as soon as possible.

Can a Cracked Car Radiator Be Repaired?

In some cases, a cracked radiator can be repaired. However, it is often recommended to replace the radiator entirely to ensure optimal performance and longevity. A mechanic can determine whether repair or replacement of the radiator is the best option.

Do I Need to Replace the Radiator if It’s Cracked?

If the crack is small and can be repaired, then it is possible to just repair the radiator.

However, if the crack is too large or if the radiator is severely damaged, then it may be necessary to replace the radiator.

Cost to Replace or Repair a Radiator

The cost to replace or repair a cracked radiator can vary depending on the make and model of the vehicle, and whether the repair or replacement is done by a professional mechanic or a radiator repair shop.

It is best to get an estimate from multiple professionals before making a decision.

How Serious Is a Cracked Radiator?

A cracked radiator can be a serious issue for your car. It can cause the engine to overheat, leading to damage to the engine and other components.

Additionally, it can cause coolant to leak out, leading to decreased coolant levels and decreased cooling efficiency.

Will a Broken Radiator Fail MOT and Inspection / Testing?

A broken radiator can cause a vehicle to fail a MOT or inspection and test, as it can indicate a problem with the vehicle's cooling system.

It is best to have a cracked radiator repaired or replaced before taking the vehicle in for a MOT or emissions test.

car being inspected


A cracked radiator can cause serious issues for your car, leading to costly repairs. It is important to be aware of the signs and causes of a cracked radiator, including low coolant levels, sludge or debris in the radiator, vehicle overheating, and leaking coolant.

If you suspect your cars radiator is cracked, it is best to have it inspected by a professional and repaired or replaced as soon as possible.


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