Blog Car Care Advice 8 Bad Radiator Symptoms You Shouldn’t Ignore (+ How to Test)
Car Care Advice

8 Bad Radiator Symptoms You Shouldn’t Ignore (+ How to Test)

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Your car’s radiator works silently behind the scenes — preventing your engine from overheating and ensuring proper coolant circulation.

But here’s the catch: problems with your radiator can stealthily creep up and catch you off guard, leaving your wallet lighter
That’s why it’s vital to recognize the warning signs early on.

We’ll dive into eight bad radiator symptoms that could signal trouble brewing under the hood and help you save some cash on unnecessary engine repair. 

Let’s begin!

This Article Contains: 

8 Telltale Symptoms of a Bad Radiator

Here are some common signs your car may present with radiator problems: 

1. Engine Overheating

The car radiator is responsible for keeping the engine cool via proper circulation of coolant (antifreeze). If you have a bad radiator, you’ll notice more frequent instances of overheating, even under regular driving conditions. 

2. Low Coolant Level or Radiator Leak

If you can spot greenish or orange-colored coolant leaking under your car, it could indicate radiator problems. Consequently, the low coolant level warning may pop up on your dashboard and your car will begin to overheat. 

Note: A radiator leak may go unnoticed if your vehicle has an extra undercarriage cover. 

Unlike an oil change, you only need a radiator flush every 30,000 miles or every 1-3 years. So, if you notice yourself filling up the coolant more frequently, it could indicate radiator issues or insufficiency. 

3. High-Temperature Readings

Persistently high readings on the temperature gauge are also one of the most common bad radiator symptoms. This can indicate insufficient coolant use, which can lead to overheating and severe engine damage. 

Keep an eye on the temperature gauge while driving. If you notice it climbing into the red zone with little to no engine strain, there’s a good possibility that you need radiator service.

4. Dirty Coolant and Radiator Sludge 

Normally, the engine coolant or radiator fluid is vibrantly colored and maintains its liquid properties at every point in its cycle. Clean coolant will change color or lose viscosity if it mixes with contaminants like radiator rust, oil leaks, and transmission fluid.

So, if you notice a sludgy, discolored buildup in your radiator or around the area, this could mean that there’s a leak in the system, causing the radiator fluid to mix with oil or transmission fluid. 

5. Transmission Issues

Rough shifting often occurs when the transmission fluid mixes with the thick antifreeze (coolant). This leads to grinding or otherwise rough shifting, which can indicate cracks in the radiator housing. 

6. Heater Malfunction

The cabin heater works with the efficient cycling of coolant in the heater core system. This gives you a warm burst of air through the vents. 

Clogs or leaks from the radiator can result in little to no heater function, as there isn’t enough hot coolant cycling to produce warmer air for the cabin. 

7. Corrosion 

Engine coolant shouldn’t normally eat away at metal or cause corrosion. In fact, it has chemical components called inhibitors to keep it from doing so. 

However, if you go excessively long between radiator flush, you could see some sludge or corrosion form due to the breakdown of these inhibitors. This can lead to cracks or leaks in your coolant system. 

8. Clogged Radiator Fins

Over time, the thin metal blades or fins of the radiator can suffer damage or get clogged with debris, leaves, dirt, etc. When you have a clogged radiator, it disrupts the airflow and the radiator can’t dissipate the engine heat efficiently. 

Besides these common symptoms, car owners with a bad radiator may also notice:

Experiencing some of these signs but not sure if the radiator is at fault?
Keep reading to learn the diagnostic process.

How to Diagnose a Bad Radiator

A simple visual inspection of the radiator can’t help you figure out what’s wrong with it. Also several components of the cooling system can present the same symptoms as that of a bad radiator. That’s why you need a professional to test and confirm if you need a radiator service. 

Here’s what a mechanic will look for to rule out other cooling system issues and diagnose a failing radiator: 

  1. Failed thermostat: They’ll use an infrared temperature gun to check the upper and lower radiator hose on your car. If both the hoses show cold readings or only one hose is hot — you have a bad thermostat. 
  1. Radiator clogs: They’ll check for both internal and external clogs that could prevent the flow of coolant and air respectively. They’ll also look for a collapsed radiator hose that may be obstructing coolant flow. 

    Note: They’ll also inspect the heater core for any clogs. 
  1. Coolant leak and faulty radiator cap: They’ll perform a pressure test to check for any leaks from a faulty radiator cap. They may further add a coolant dye and rev your engine to spot any slow coolant leak. 

    Note: A collapsed radiator hose could also signal a faulty cap that may be causing a vacuum in the cooling system. 
  1. Faulty water pump: After they rule out a bad thermostat, they’ll check if the coolant isn’t circulating from the water pump. 
  1. Cooling fan damage: They’ll inspect the cooling fan if it turns on as the engine temperature begins to rise.

If all these cooling system components are working fine, it’s likely a failing radiator. 
But what if you don’t get these checks done soon? 

Is it Safe to Drive with a Radiator Problem?

No. Driving with signs of a bad radiator isn’t advisable as it can cause your car’s engine to overheat. Excessive heat can lead to a blown head gasket and irreversible engine damage. 

So, if you notice the temperature gauge hitting its max limit, it’s best to pull over and get your car towed to your service department. 

Wondering how much you’ll need to pay for this fix?
Let’s find out. 

How Much Does a Radiator Replacement Cost?

You can expect to pay anywhere between $600 to $1200 to install a new radiator. 

This cost can vary based on your car’s age, make and model, radiator material, and labor charges in your area. 

Aluminum radiators are less expensive due to their lightweight and efficiency in dissipating heat quickly. Meanwhile, copper and brass radiators are more expensive, corrosion-resistant,  and commonly found in older cars.

However, in many cases, you may only need a small radiator repair rather than a complete replacement. Here are the estimated repair costs a parts department may change for different radiator fixes (including labor): 

Next, let’s clear any additional doubts you may have. 

3 FAQS on Car Radiators

Here are answers to some common questions on car radiators: 

1. What Does a Radiator Do?

The car radiator is an essential part of your vehicle. It works as a heat exchanger — transferring heat from the hot coolant to the surrounding air to prevent engine overheating. 

Here’s how: 
The coolant absorbs heat from the car’s engine and flows to the radiator, where it releases heat to the air passing through the radiator’s fins. The cooled coolant is then pumped back into the engine. This coolant flow helps regulate the engine’s temperature and ensures optimal performance.

2. How Long Do Radiators Last?

If you follow proper car maintenance and driving best practices, your radiator could last for 8-10 years. 

But if you start noticing any bad radiator signs, you should get it fixed ASAP to prevent severe damage to your car. 

3. Is It a Faulty Radiator or a Bad Radiator Cap?

To distinguish between the two, check for these signs: 

Consider checking the radiator cap first. Conduct a coolant pressure test and visually inspect the radiator cap for any damage. If issues persist, you’ll need to contact your mechanic for a radiator diagnosis. 

Maintain Your Vehicle’s Cool with a Working Radiator

If you’ve noticed any signs of radiator problems like an overheating engine or leaks under the car, you must address these issues promptly. It can save your vehicle from severe damage and costly repairs. It’ll also ensure your car runs smoothly for miles to come.

Looking for a convenient auto repair solution?
Consider AutoNation Mobile Service

Our expert automotive technicians can diagnose and address radiator issues right from your driveway, saving you time and hassle. 

Contact us today to schedule a radiator repair, wheel alignment, brake repair, oil change, or any other automotive repair service.