Clogged Radiator: Causes, Symptoms, and Fixes

A radiator is one of your car’s vital organs. It’s particularly important for your engine — the radiator prevents it from overheating by absorbing the heat from the coolant. Once the coolant cools down in the radiator, it’s sent back to the engine. And while this process is normally pretty smooth, a bad or clogged radiator can cause a number of problems and even lead to permanent damage to the engine.

To avoid costly repairs and engine replacement, you should know some of the most common causes and symptoms of a clogged radiator. Reacting as soon as you notice a problem could save you thousands of dollars. And if you’re looking for a guide to help you fix a clogged radiator on your own, look no further — I have just the solution for you.

Symptoms of a clogged car radiator.

Common Causes of Clogged Radiators

Radiators can be surprisingly sensitive, so if you hope to keep yours in good shape as long as possible, it might help to know what leads to its clogging. Here I will show you the three most common causes:

Old Coolant or Radiator Fluid

That’s right, the very fluid that keeps your engine going can cause your radiator to break down. But keep in mind that this only happens if you don’t change it often, or even worse, if you never change it. Contaminants and rust can build up in the fluid over time, and block the pipes and fins of your radiator. To make sure this doesn’t happen, I recommend you change the fluid every two to three years.

Outside Elements

Dirt, leaves, sand, insects — these are all natural enemies of your radiator. They can clog up the fin tubes and even cause them damage at high speeds. After all, fin tubes are extremely delicate, so they can bend and break quite easily. To avoid this, you have to properly maintain and clean your radiator.

Inappropriate maintenance

However, it’s not only the outside factors that cause damage — sometimes it’s you. Lack of maintenance may be damaging to your radiator, but inappropriate one, such as spraying it with water, is just as bad. If the water jet is too strong, it can twist and bend the sensitive fins. So if you wash your radiator, make sure to do it gently.

Symptoms of a Clogged Radiator

No matter how many times you change the coolant or clean the fins, your radiator might still end up clogged. If that happens, you’ll want to minimize the damage, and this is only possible if you react as soon as you notice something is amiss. Here are a few telltale signs that your radiator is no longer doing its job:

Leaking Coolant

You might notice some strange drops in your driveway or on your garage floor. If these are accompanied by a sweet smell and steams from the radiator tank-seam, you’re definitely dealing with a leaking coolant. Coolant leaks out when the radiator fins become corroded or so clogged that the fluid can no longer circulate. If you don’t take care of this, it can lead to permanent radiator damage.

Engine Overheating and Temperature Warnings

If your engine starts overheating, you can safely assume that something’s wrong with the radiator. After all, its main job is keeping the engine cool enough to function properly. Pay attention to the temperature readings on the gauge and you’ll notice if the needle is more often in the red zone than usual.

However, keep in mind that engine temperatures can be higher for reasons other than overheating. In the summer, temperature readings will naturally be closer to the red zone, but you only really need to be concerned if this happens constantly. After all, engine overheating can cause a host of problems which you can read about here.

Discolored Coolant

If you’ve never thought about the color of your coolant before, this might be the right time to start. Normal coolant should be bright green or yellow, though you might come across other colors. What it shouldn’t be is the color of rust or oil — this means that it’s contaminated and therefore dangerous for your radiator.

Another sign of contamination is the thickness of the coolant. Normally, coolant is completely fluid and it easily passes through the radiator. But if its texture becomes thicker, it might start creating a sediment buildup and clogging your radiator. Pay attention to what your coolant looks like, as it’s one of the most obvious signs of a bad radiator.

Damaged Water Pump

If your radiator is clogged, coolant can’t properly flow into the water pump. Without the proper lubrication from coolant, your water pump will soon suffer damage. This happens because of the metallic parts grinding and scraping against each other, which causes friction and builds up pressure.

Passenger Area Heaters Not Working

Are you freezing in your car and the cabin heaters are refusing to cooperate? A clogged radiator might be the culprit! After all, the passenger area heats up when hot coolant passes through the heater core, and the fans blow the resulting hot air into the cabin. If the radiator is clogged, less hot coolant will pass through the core, and thus you won’t receive enough heat.

Of course, there are other, more probable causes of the cabin heater’s malfunction. But if everything else fails to explain it, do check your radiator, especially if you haven’t done it in a while.

How to Unclog a Radiator

Fixing a clogged radiator isn’t difficult — in fact, you could do it yourself! All you need is my guide and your radiator will once again be as good as new.

Here’s how to unclog a radiator step-by-step:

  1. Let your engine cool down and drain your radiator. You’ll do this by placing a bucket under the radiator drain petcock. Drain your radiator completely, there should be nothing left inside.
  2. Remove the radiator fill cap and pour some radiator flush. It’s best to use a heavy-duty one like Gunk C2124.
  3. Fill the remainder with water and put the radiator fill cap back.
  4. Let your car run for 15 minutes. The radiator flush should pass through the entire cooling system during this time, but you can let it run longer if you think it’s necessary. Then let the engine cool off.
  5. Open the drain petcock and let the radiator flush drain into the bucket.
  6. Remove the cap again and put a water hose in. Wash the cooling system until the water that’s draining into the bucket becomes clear. This should indicate that the radiator isn’t clogged anymore.
  7. After the water drains, fill the system with coolant and water. Don’t leave any air, as it could cause the engine to overheat.
  8. Let the engine run for 15 to 30 minutes, but don’t drive yet. The purpose of this is to let the coolant circulate and fill in any remaining air pockets. As the air pockets fill, the coolant level will drop. So after this process ends, you can once again refill the coolant to reach a satisfying level of it.

Whenever your radiator clogs, you can follow these simple steps to clean it. And if you’re still not confident in your skills, or you are more of a visual learner, there is a number of Youtube tutorials that can show you exactly how to do this. For example, I recommend this one.

In Conclusion

If you maintain your radiator properly, you can prevent the clogging and corrosion that occurs over time. And while prevention is better than cure, you should still know how to spot the symptoms of a bad or clogged radiator. After all, if your engine overheats, it won’t be just your wallet that suffers — your life can be in serious danger if this happens while you’re driving.

So for your own safety and the safety of others, take good care of your car radiator.




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