Bad Radiator: Signs, Symptoms, and Replacement Cost

Your car's radiator plays an important role in keeping your engine and all of its moving parts from overheating.

An overheating engine could be detrimental to your vehicle and your wallet, and it is just one of the signs of a failing radiator. Other signs include low coolant levels, coolant leaks, lack of interior heating ability, and the presence of thick or discolored fluids in the radiator itself, all of which should immediately be addressed by a mechanic.

What Is a Radiator?

A radiator is the primary component of a vehicle’s cooling system. It sends hot coolant from the engine over a series of small tubes that are exposed to natural airflow from driving, cooling down the coolant liquid and recirculating it back through the engine to help it remain cool. When airflow is not enough to allow for complete cooling, the radiator fan will turn on to assist with additional airflow.

Common Signs and Symptoms of a Bad Radiator

Because your radiator is so integral to the proper function of your engine, any of the signs and symptoms of a failing radiator should be further investigated to ensure that no engine damage is occurring or has occurred. Ignoring these signs and symptoms could result in an engine rebuild or replacement, a much more expensive prospect than a visit to your local mechanic.

Engine Overheating

Engine overheating is the primary sign that your radiator is or has failed. Your engine has many moving components that function at high speeds. Insufficient cooling causes increased friction, resulting in heat buildup. Enough heat buildup can cause internal component melting, ultimately resulting in the need for an engine replacement. 

Coolant Leaks

leaking coolant

Your cooling system does not just include your radiator. Any leaking along the cooling system of your car should be cause for concern, but radiator leaking means that the largest part of your cooling system is experiencing problems. The good thing about radiator leaks is that they are usually fairly obvious, leaving puddles of coolant on the floor. Some cars with additional underbody panels may obscure leaking.

Low Coolant Levels

Low coolant levels are often the result of a leak somewhere within the system of your vehicle. Another reason for cooling levels is the insufficient addition of coolant after a system flush. Regardless of the reason, low coolant levels are not always easily identifiable and are often the cause of engine overheating. If your engine is overheating, coolant levels should always also be checked.

Discolored or Sludgy Coolant

Normal coolant is a yellow or bright green color. Radiator rusting, oil leaks, and transmission fluid that infiltrate the cooling system will mix with clean coolant and change its color or cause it to become less viscous. Sludgy coolant is not able to circulate properly through the cooling channels of the engine, and again, overheating is usually the result. Discolored coolant should also be cause for alarm since the only fluid designed to be in the cooling system is coolant.

Vehicle Interior Heating Issues

Turning on the heat in your car and not feeling any heat can be inconvenient and uncomfortable, but it may also be a sign of a radiator issue. The heat produced by the engine, carried away by hot coolant, is used to heat the cabin of your vehicle. A malfunctioning or clogged radiator can cause a lack of interior heat.

Damaged or Clogged Radiator Fins

damaged radiator

Radiator fins are the small hoses that run from one side of the radiator to another. Usually damaged or clogged fins are what causes the signs and symptoms of a radiator failure, but they can also be a sign of radiator failure. The radiator is usually one of the easier things to physically see when you look at a vehicle or open the hood, making radiator damage easily identifiable.

Transmission Issues

A less common symptom of radiator failure is transmission issues. This is only present on vehicles with a transmission cooler that is linked to the main cooling system of the vehicle. Transmission issues occur when the cooling system leaks coolant into the transmission cooler or vice versa. This causes incompatible fluids to mix, which can ultimately lead to transmission failure, radiator failure, or both.

Check Engine/Engine Temperature Light

Very few signs and symptoms lists would be complete without mention of the check engine light. Radiator failure in and of itself will not usually cause the check engine light to come on. Rather, the failure of the radiator will usually affect other systems, causing the check engine light to illuminate. 

Most cars also have an engine temperature light that will illuminate if the engine temperature rises to dangerous levels. 

What is the Expected Lifetime of a Radiator?

Radiators can last for the lifetime of a vehicle that is taken care of, used regularly, and engineered well. Most can last for well over 100,000 miles, or about 10 years, under these conditions, but there are several reasons that radiators can fail prematurely.

Clogged Radiator

Because the radiator needs to be exposed to airflow, they are often placed in the front or the rear of a vehicle and are always somewhat exposed to the elements. This can cause debris and dirt to damage and clog the tubing. Prolonged exposure to these elements or particularly dirty conditions can cause the radiator to fail quicker than normal.

Engineering Defects

Engineering defects and poor design are not the most popular reasons for premature component failure, but it does happen, probably more often than many people realize. It can happen with any component, including the radiator. The most common radiator defects cause fluid leaks.

Radiator Cap Failure

A car's cooling system is pressurized. If the radiator cap or any of its seals are faulty, damaged, or incorrectly sealed, it will cause issues with the radiator and the entire cooling system. 

Head Gasket Issues

A head gasket is one of the most important components of an engine, and a bad one, or one that fails, can cause a slew of other failures within other various vehicle systems. A bad or failed head gasket is usually not the direct cause of premature radiator failure, but it can certainly contribute to it, along with many other car issues.

Learn More: Signs and Symptoms of a Cracked Cylinder Head

How Much Does a Radiator Cost to Replace?

A replacement radiator usually costs anywhere between $300 and $600 depending on the vehicle make, vehicle model, size of the radiator, and quality. Labor costs in addition to parts can also vary, mainly on the car make and model

Some cars have easily accessible radiators that require a minimal amount of work to remove and replace. Others require the removal of various brackets, components, and sometimes even the entire front of the vehicle. The more involved it is to access a radiator, the more labor costs a customer will incur. Total costs can be anywhere from $600 to $1400.

Final Thoughts

Your vehicle’s radiator is a very important component. It is responsible for cooling hot coolant from the engine by sending it through tubes that are exposed to airflow. When the radiator fails, it could cause major issues. If your cars experiences engine overheating, coolant leaking, discolored coolant, transmission issues, or the illumination of the engine temperature warning light, you should see your local mechanic immediately. 

Shawn Furman
I have been a vehicle hobbyist for as long as I can remember as well as a freelance writer for the past three and a half years. My clients have included Vehicle Scene, Autolist, CarGurus, and now The Vehicle Lab. In addition to my current clients, I also maintain my own blog where I am able to share my knowledge and experience through vehicle reviews, car-buying guides, how-to guides, and list articles.
The Vehicle Lab looks to cover all aspects of the automotive industry: News, Maintenance & Repair Guides, and Product Reviews
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