When an engine runs, it produces heat. The purpose of the radiator is to cool the engine and prevent it from overheating. A car engine uses coolant to absorb heat and transfers it to the radiator where it cools. Once it cools down, the coolant is sent back to the engine and the process starts all over again.
When your radiator is clogged, not working as efficiently as expected, or has simply gone bad, it’s not cooling enough inside the engine. This can lead to your car overheating and, if not fixed soon enough, permanent damage to the internal parts of your engine.
A radiator can be clogged on the inside, on the outside, or just fail. Here are some signs of a clogged radiator you’ll want to look for before costly engine damage occurs.
Common Symptoms of a Failed or Clogged Radiator
#1 – High-temperature gauge readings
Since a working radiator prevents the engine from overheating, you’ll know something is wrong with the radiator if the engine starts to overheat.
Check the temperature gauge to see if the readings are higher than normal or if the needle is in the “red” zone. Some newer cars will display the temperature digitally and warn you when the engine temperature is too high.
A normal operating temperature for most cars is between 195 and 220 degrees F. If the temperature falls slightly outside that range, it’s often no cause for alarm, especially in the summer months when the air conditioning runs constantly.
But if the temperature consistently stays on the hot side, you may have a clogged radiator. This usually occurs due to corrosion due to rust, internal deposit buildup over time, or debris getting stuck in the radiator, preventing the proper amount of coolant from circulating through the radiator and your engine.
#2 – Coolant Leaks
The cooling casing or fins can develop small holes or cracks when the radiator is clogged due to a heavy buildup of rust. Once this happens, you may be able to see small droplets of coolant on your garage floor or driveway.
Rust inside your radiator is often caused by poor quality coolant or by adding tap water (rather than distilled) to the coolant mix which has a lot more contaminants. If the radiator is not flushed regularly, more and more rust will form and start to corrode the radiator tank.
Even with the slightest coolant leak, your vehicle will be forced to operate with an insufficient amount of coolant and the low coolant light may illuminate your dashboard.
If you don’t fix the leak as soon as possible (or at least keep the coolant level topped off), your engine can overheat and even require expensive repairs due to internal damage.
#3 – Fluid Discoloration
The vehicle’s coolant should be a bright green or yellow (or sometimes red or pink) color and flow freely through the radiator and coolant passages inside the engine.
Over time, internal deposits and even sludge can contaminate the coolant. This will make it a more rusty color or even the color of the oil. Checking the coolant overflow tank is often the easiest way to check the condition of the coolant.
This contaminated fluid will also be slightly thicker and will not allow it to flow easily through the cooling system. This, in turn, starts to clog the radiator and if you let it deteriorate long enough, the radiator’s efficiency can drop to the point of causing your car to overheat. A radiator flush should be performed as soon as possible.
Also, some vehicles have a transmission cooler located inside the radiator. If a leak occurs in the barrier that separates them, the coolant and transmission fluid would mix and cause twice the trouble.
#4 – Blocked Outer Radiator Fins
The radiators are designed for maximum cooling. To achieve this, thin fin tubes run through the front of the radiator. These tubes carry hot coolant. As you drive, the radiator fan pushes outside air over and around these fins to lower the temperature of the coolant before it returns to the engine.
If these tubes become clogged with dirt, bugs, leaves, or other material, the airflow is blocked, not allowing the coolant to cool as much as it needs to.
In most cars, there’s usually enough access (you may need to remove a plastic cover or two) to use a garden hose and spray nozzle to wash away any debris that may be blocking the front of the radiator.
#5 – Bent or damaged fins on the radiator
In addition to becoming clogged due to foreign material adhering to the front of the radiator, airflow can also be blocked when enough fins are bent or damaged. These fins are extremely delicate and a small piece of gravel hitting them while driving can cause damage.
Damage can also occur during the installation of a new radiator or even when spraying water to clean the fins.
If too much water pressure is used, such as when using a concentrated stream or pressure washer, the fins can easily bend and block airflow. When enough fins are damaged, it can clog the radiator enough to cause the engine to overheat.
#6 – Heater for passenger area not working
A car cabin heater relies on hot coolant passing through the heater core and then the resulting hot air being blown into the passenger area by a fan. If the radiator is clogged or leaking, not enough hot coolant is getting to the heater core to allow proper heating of the car’s interior.
A faulty thermostat is usually the problem, but sometimes a problem with the radiator can be to blame.
Average Radiator Replacement Cost
The cost to replace a radiator is one of those things that can vary quite a bit. In general, you can expect to pay somewhere along the lines of $200 to $900 total to replace a radiator with most vehicles in the $400-$500 range.
A typical radiator with an aluminum core and plastic tanks can run anywhere from $100 to $600 depending on the make and model of the vehicle and whether it is OEM or aftermarket.
Something like a Ford Focus radiator will be on the low end, while something like a Chevy pickup with a large Duramax engine (with built-in oil cooler) or a luxury car will be on the high end.
The amount of time it takes to replace a radiator also varies. For some cars with easy access, it can be a 1-hour job, while some more strict and complicated setups (for example Audi or Porsche) can take close to 3 hours. Expect to pay somewhere in the neighborhood of $100 to $300 for labor.
Additionally, other parts may also be required as part of the job. The new coolant is usually needed, and sometimes the hoses, hose clamps, radiator caps, and thermostat are also replaced at the same time. Factor in an additional $15 to $100 in miscellaneous pieces.