How to Unclog a Radiator [6 Step Guide]

By Jed Lehman •  Updated: 08/18/22 •  7 min read

Wonder how to unclog a radiator? You’re in the right place. A radiator is an essential component of your car’s cooling system, and if it becomes clogged, it can cause your engine to overheat. This can take a major toll on your engine’s lifespan. It also means you’ll have to stop driving and get it fixed ASAP so you don’t end up stranded.

If you notice that your car’s engine is running hotter than usual or the temperature gauge is reading in the red zone, it’s time to check your radiator.

We are going to walk you through the signs of a clogged radiator as well as exactly how to unclog your radiator so you can get back on the road as soon as possible.

Table of Contents

What is a Car Radiator?

Over time, dirt and debris can build up inside your radiator, which causes it to clog. This clogging prevents the coolant from flowing freely and results in the overheating of the engine.

Why Is My Radiator Clogged?

There are a few common reasons your car’s radiator can become clogged.

The most common reason is that the coolant level is low, which causes the coolant to become concentrated and can lead to deposits forming in the radiator.

Another possibility is that there is a leak in the radiator hose or radiator itself, which allows coolant to escape and causes the level to drop. If the coolant level gets too low, it can cause the engine to overheat. That’s why it’s so important to check it regularly and top it up if necessary.

Signs You Have a Clogged Radiator

A clogged radiator can cause all of these problems and more, so it’s important to get it fixed as soon as possible. If you’re noticing any of the following signs, it may be time to take your car in for a checkup:

Your Engine is Overheating

If your engine temperature gauge is in the red zone or you see steam coming from under the hood, your radiator is probably clogged.

Your Car is Leaking Coolant

Coolant is what keeps your engine from overheating, and if you’re leaking it, your engine could overheat and cause serious damage. A band-aid fix you can implement immediately is to locate the leak and put some duct tape over it to temporarily patch it.

You See Rust or Sediment in Your Coolant

If you see rust or sediment in your coolant, this is almost a sure-fire sign of a clogged radiator, and it’s time to take action. If this happens, the engine might stop working altogether. It’s important to get your car fixed as soon as possible so that the problem doesn’t become more serious.

If you notice any of these signs, it’s important to have your car fixed immediately. Do it yourself, or have it evaluated by a mechanic as soon as possible.

How to Unclog Your Radiator

Here’s how to unclog a radiator quickly and safely:

  1. Park your car in a safe place and turn off the engine.
  2. Let the car cool down for at least 30 minutes before beginning any work on the radiator.
  3. Locate the drain plug at the bottom of the radiator.
  4. Place a large container beneath the plug to catch any coolant that may spill out when you remove the plug.
  5. Use a wrench to loosen the drain plug and allow all of the coolant to drain into the container. Be careful not to spill any.
  6. Finally, flush the radiator with a cleaning agent or water to remove any remaining debris.

What to do if the Clog is Severe

If the clog is severe, you will need to remove the radiator and take it apart. This can be a bit challenging, but it’s totally doable.

The most important thing to remember when taking a car radiator apart is to make sure that the engine is cool before starting.

1. Remove Upper and Lower Hoses From Radiator and Reservoir

To do this, you must first release the hose clamps. You can achieve this by using a hose clamp remover or channel locks to squeeze the hose clamp ends together. After the ends are attached, the clamp should be sufficiently loose to allow the radiator hose to slide up and off the radiator.

2. Take the Transmission Cable Off

In some automobiles, the radiator may incorporate a cooler for the transmission fluid. You will need a wrench to remove any metal lines that connect the transmission to the radiator. When you disconnect these connections, be cautious to catch any transmission fluid that seeps.

These will consist of two metal lines that will enter the radiator’s base. Do not bend these.

3. Unplug the Electrical Wiring Harness

Find the electrical connector for the fan motor, then remove it. Usually, this is the only electrical connection, but be sure by checking twice.

4. Detach the Condenser of the Air Conditioner

Often times, the radiator is linked to the condenser of the air conditioner. In order to remove the radiator, you need to remove the condenser mounting bolts. The bolts for installing the condenser are usually located close to the radiator’s top corners.

5. Remove the Mounting Bracket Bolts

Take a look at the way your car’s radiator is attached. On top, braces are often bolted to the frame, while the bottom usually rests on rubber feet inside of a depression.

6. Take the Radiator Out

With the electrical connectors and hoses removed, there should be enough room to take your radiator out. If not, look at the top engine mount and the battery tray. These are two other parts that you might need to detach.

7. Take the Radiator Apart

After you have finished steps 1 through 6, you should be able to remove your radiator. Make sure you keep all of the components to put them back in after you have found and fixed the clog.

How to Prevent Radiator Clogs

The best way to prevent your car radiator from clogging is to have it flushed and refilled with fresh coolant every 30,000 miles.

You should also check the radiator hoses regularly for cracks or leaks. If you notice any problems, replace the hoses as soon as possible.

What Will Happen If I Leave the Clog in the Radiator?

If you leave the clog in the radiator, it can cause a number of problems. The most serious problem is that the clog can cause the radiator to overheat. This can lead to engine damage or even a fire. Additionally, the clog can prevent coolant from flowing through the radiator, which can lead to engine overheating.

Finally, the clog can cause the radiator to leak coolant, which can be dangerous if it leaks onto hot engine parts.


With these easy steps, you should be able to unclog your radiator in no time. Remember to always be careful when working with fluids and heat, and if you have any doubts or concerns, consult a professional. With a little elbow grease (and maybe a trip to the auto parts store), you can get your radiator back up and running in no time.

Jed Lehman

Jed Lehman is a born gearhead who has been working on cars since he could crawl. He inherited his love for auto from his grandfather who owned a maintenance shop in Carlsbad, California. Jed is the driver behind Gearshift, and started this site to provide straightforward, helpful automobile information. From maintenance tips to product reviews, you can find it all here.