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how to use radiator stop leak

Radiator Stop Leak is known as a product for helping to alleviate a leaking radiator. It is used to seal a leak that’s happening somewhere in the cooling system.

It’s obviously not fair to have a leak in your radiator. Also, it’s not possible each time to change the radiator for a permanent solution. So, it is needed sometimes to use a radiator stop leak for a temporary repair. But, it is highly effective to stop the problem.

 Read full review Best Radiator Stop Leak here 


It is applicable for all “water” cooled systems of petrol, LPG and diesel engines when minor leaks are noted. It can also be used as a preventive agent.


When you will start the process, you may have some problems, like toxic liquid touching your skin and liquid or dirt spray into your eyes. For such a situation, you must use safety goggles and gloves. The gloves will help you to prevent any toxic liquid from touching your hand or from burning by touching something hot. The goggles will protect your eyes from any toxic spray.

Here are some of the tools you’ll need:

  • Drain pan
  • Safety goggles
  • Gloves
  • Hosepipe
  • Dry towel
  • Radiator stop leak
  • Water
  • Coolant
  • Coolant system pressure
  • Wrenches of assorted sizes.

Instructions On How To Use Radiator Stop Leak?

Step One: Identifying a leak in the radiator

When there is a leak in the radiator, it will result in lost coolant and compromise the system’s ability to reduce radiator dissipated heat. When your coolant system begins to fail, the temperature gauge on your dashboard will climb. So, if you are having issues with overheating, you may have a leak in your radiator.

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First thing you should notice puddles of coolant from under your vehicle. It may be any of the fluids in a vehicle’s engine that may leak, but you need to look closely and possibly even touch the fluid in order to properly identify it. A pool of green or other colored liquid under your car is a sure sign that your radiator is leaking.

If you are still not able to identify the leak, you should try the marking. Mark the coolant level in your first inspection. After a few minutes, do the second inspection. If the coolant level is lower from the first inspection, it means that there is a leak somewhere in your radiator.

Step Two: Allowing the engine to cool

Next, you have to detect the position of the leak. But first, allow the engine to cool. You should always keep in mind the safety issues. Otherwise, you have to pay more price. If the engine is not cooled properly and you try to remove the radiator cap, it can expel heated coolant and steam that can be dangerous. So, wait for a few hours. Then inspect the engine if it is properly cooled or not and then you can touch the engine to start your next steps.

Step Three: Washing the radiator with a hose

To locate the leak easily, you need to wash the radiator and clean it. You can use a hose to spray the radiator and surrounding components. Wash properly to remove dirt and excessive rust. After washing the radiator, look for any signs of cracks in the radiator itself or on either of its end tanks. If there are any leaks or cracks in the radiator, this washing will help you to find the leak easily. It is unnecessary to use soap when washing your radiator. You can use paper towels to wipe away any areas of excessive grime or rust.

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Step Four: Locating the leak

After washing, start the engine and take a close look at the radiator and the surrounding engine for a leak sign. You will see steam or fluid spraying out of the place where there is a leak. Also, you can see coolant or water dripping down the radiator or piping. Otherwise, you may hear the hissing of a leak that you aren’t able to see from your vantage point. Follow the sound and detect the place.

You should check the excessive rusted areas. These place are mostly leaked.

Also, you can use a coolant system pressure to locate the leak. But, be careful about the pressure, it should not be more than 10 to 15 pounds. If the pressure is higher, it could create more leaks in the radiator. Then it will be almost impossible to repair and you have to change the radiator.

These are the ways by which you will surely find the leak in the radiator.

Step Five: Purchasing Radiator Stop Leak

As you have found the leak, now you need to purchase a Radiator stop leak. It will help you to repair the leakages in the radiator, cooling, and heating system. There are a number of radiator stop leak in the market and they are easy and safe to use. From any automotive product shops, mechanic shops, department stores, or hardware stores, you can purchase it for your use.

Step Six: Stopping the engine and cooling the radiator

Now, stop the engine if it is on. Make sure the engine is cooled. Before pouring the Radiator stop leak, the engine must be cooled properly. Never start the process if the radiator is hot. Otherwise, it will be a good way to be scalded.

Step Seven: Pouring the Radiator stop leak

First, shake the bottle properly. Unscrew the radiator cap and pour the Radiator stop leak directly into the radiator. Normally, it needs one full bottle. Try to pour it in without draining any coolant out.


Step Eight: Adding radiator fluid

Add the radiator fluid. Use the radiator cap to add the fluid until the level of coolant is equal to the amount that has been recommended by the maker of the Radiator stop leak product. Now close the radiator cap properly.

Step Nine: Starting the Car

Start the car and allow the engine to warm up. Let the temperature rises up to the operating temperature. This will circulate the plastic sealant through your cracked radiator and help to plug any small pinholes as well. Run the car for approximately 5 to 10 minutes to thoroughly coat the radiator. It is a good idea to turn on the heater to allow the coolant to flow through the heater core as well. Keep an eye out for leaks to ensure that the repair worked.

Step Ten: Filling the radiator

Stop the car to fill the radiator with a 50/50 mixture of water and coolant to top off the cooling system.

Step Eleven: Allowing the car to sit overnight

Allow the car to sit at least 12 hours so that the radiator sealant can set up properly. In this time period, you must not start the engine. It will hamper the process and the leakage cannot be repaired properly. After this process, your car will be ready to drive.

Though the Radiator stop leak is not a permanent solution it is easy and effective. Most of the time, the plastic sealant will eventually wear out and the leak will return. Once you have one leak, others are likely to appear later on. Most of the time it can work only for a year. The only permanent solution is to change the radiator.

However, using a Radiator stop leak is the best way of instant prevention of your engine from damage.

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