radiator epoxy

Radiator Epoxy – Tutorial on Radiator Crack Repair

This post may contain affiliate links. We may earn a small commission from purchases made through them, at no additional cost to you.

Repairing a leaking aluminum radiator can be a challenge. But, if you have a bit of knowledge about cars you can do it yourself using a radiator epoxy. All you need to do is locate the leaking area and then make sure you clean the radiator thoroughly before applying the epoxy. Interested in finding the best plastic radiator repair epoxy? Follow our guide to find out.



Radiator Epoxy

Leakage is very common when your automobile radiator ages. Unfortunately, new radiators are expensive and not everyone can afford to buy them when the car starts to leak. But, with the radiator epoxy, you can repair your radiator and extend its working life.

When repairing an aluminum radiator, there’s no need to hire a professional because you can do it yourself. But extra care is needed when handling the epoxy because it contains harmful ingredients.  Always wear gloves when using the epoxy and when you are done, make sure you keep it in a place where kids cannot reach. Below is a guide on how you can apply the radiator epoxy to repair your car from leaks and cracks.

radiator crack repair



Repairing Radiator Cracks and Leaks

The radiator is the car’s cooling system; it is responsible for transferring the fluids inside to the air outside. Once the inside fluid is cool, the engine also cools down.  The minute you notice any signs of leakage, it is very important to find a solution.


Finding the Problem

Leakage is the most common issue with radiators. When the hoses that connect your radiator to your car fail and loosen up, you will notice some fluids under the car. But you have to make sure that it is not just water. Once you find the problem, you can use the best epoxy for plastic radiator repair to fix it.


Cooling the Engine

The first thing you need to do when repairing the leakage on the radiator is to switch off the engine and make sure it is cool. Then remove the radiator from your car, this will help you to work on it more efficiently. However, removing the radiator is not an easy task. It’s a bit complicated and may need a professional. Old models are not that complicated but new models will give you a hard time.

After locating the leak, the next step is to drain the radiator just under the damaged part. Then clean the damaged area with a brake cleaner. Cleaning the area properly before you apply the epoxy is a must or else it will not stick and your radiator will continue leaking.

Note, it is very essential to properly clean the damaged area before applying the epoxy. Any dirt or dampness will affect the bonding process of the epoxy. After cleaning and making sure the area is dry, you can then prepare and apply the epoxy to the leak. By following these instructions your radiator will last longer and you won’t have to spend more money on it.

best epoxy for plastic radiator repair


Radiator Crack Repair: Fixing the Leak

When the part being repaired is clean and dry, mix the epoxy in your hand till it becomes soft enough for you to smear on the leaking area.  Keep the epoxy an inch thick so that it can be able to withstand the pressure of the coolant system when the car is moving.


Best Epoxy For Radiator Crack Repair: J-B WELD SteelStix Reinforced Epoxy Putty

This is a two-part hand mixable epoxy that is steel reinforced and non-rusting. It quickly repairs or rebuilds anything made from steel and is certified by NSF. After mixing the part formula with your hand, the epoxy takes about 5 minutes to set and is ready to use after an hour.

The J-B weld epoxy has a lap shear strength of about 900PSI, this can withstand high continuous temperatures (350F) and intermittent temperatures (450). The epoxy is also chemical resistant against hydraulic fluids, petroleum, and other fluids. The J-B Weld delivers awesome results and quality.

J-B WELD SteelStik Epoxy Putty
  • A steel reinforced epoxy putty stick
  • Easy to use and works on multiple metal surfaces
  • Extremely durable 900 PSI strength
View on Amazon


  • Hardens quickly
  • Can repair small damages permanently
  • It is chemical resistant
  • It is electrically insulating and cam withstand heat
  • Steel-reinforced
  • Creates an extremely strong bond over various metal surfaces
  • Quick to dry and easy to work with


  • A more expensive adhesive
  • Contains ingredients that are toxic so always wear gloves and take care when using it


How to Apply Radiator Epoxy

Once you have found the best epoxy for plastic radiator repair, its time to apply it. When the epoxy is properly mixed and prepared, you can then apply it to the leaking area. Be cautious when applying. Make sure you don’t miss any part and it should be correctly applied so that when the pressure builds up inside the radiator, it should remain strong. Allow the epoxy to sit for a couple of hours before using your car.

Note, make sure you wear gloves when using the epoxy and after you are done, you should thoroughly wash your hands with soap.  This product contains ingredients that may be toxic to your health.


Inspect Your Work

Make sure you inspect your work before you start using your car again. First of all, you should put everything back to where it’s supposed to be. Then take a look at the patch to see if it’s still bonding perfectly. Start the car to see if the radiator is fully patched. Make sure you leave the engine running in order to build up pressure and to see if everything will still remain in place. After a few minutes of observations, and if everything still looks good then you have successfully repaired your radiator.

how to fix a cracked radiator plastic


How to Fix Cracked Radiator Plastic

Replacing a radiator can be very expensive than simply repairing it. Repairing a plastic radiator is straight forward and does not require much equipment. Just make sure the epoxy you choose will be powerful enough to handle high temperatures from 200oF and above. Plastic radiator tanks have glass-reinforced nylon consisting of softening features, this helps the radiator to withstand high pressures. Now, let us look at the ways of fixing a cracked radiator plastic:

  • Open the petcock and drain all the liquids into a container, this will prevent any liquid from spilling while you are working. Then clean up the damaged area and make sure it’s dry.
  • Make sure you use a heat gun to soften the area, then you will see the crack groove and the surrounding area becoming glossy.
  • Then melt a nylon rod into the groove using the plastic welder. When the rod melts on the damaged area, the color of the rod will change to brown. After that use the welder head to merge the melted nylon with the radiator plastic.
  • Make sure you blend until you get an even surface, this will ensure a stronger repair. Allow the blended area to cool down and become hard again

Note, the J-B Weld is also an excellent epoxy for repairing a plastic radiator. It works perfectly on plastic and will give the best results in a couple of hours.

radiator epoxy



Frequently Asked Questions


Can You Repair Radiator Cracks?

The simple answer to this question is yes. You simply need to locate the crack, clean the radiator properly and then use the epoxy to patch the leaking area. Cleaning the radiator before applying the epoxy will help it to stick and last longer.


Can You Use J-B Weld on Your Radiator?

J-B Weld is the perfect epoxy for all plastic radiator repair. Is it water-resistant, chemical- resistant therefore creating the world’s strongest bond to the radiator that will last for a long time. The J-B weld works well on many areas and you do not need to remove the radiator when applying it to the leaking area.


Is Radiator Epoxy a Good Option?

Absolutely, the radiator epoxy is a very effective way of repairing a cracked or leaking radiator. Although this is not a permanent solution, it will fix the radiator and have your car running again for a longer time.


How Long Can You Go With a Radiator Leak?

The radiator is a very essential part of the car. Therefore, the minute you notice any leakage it is important to find a solution to it. Do not wait for the problem to become big because it may require a lot of money to get it fixed properly.

However, if the damages on the radiator are already large, the best thing to do is to replace it before it does any more damages to your car. If you want your radiator to last longer, always check for leakages and cracks and make sure you handle the problem before it becomes big.


Repairing your car’s radiator is an important skill to know for keeping your vehicle in good running condition. Do not wait for the problem to grow bigger because it will cost you a lot of money to get it fixed. Take care of the problem as soon as you notice it. Using plastic radiator repair epoxy, you get a simple solution that you can easily do at home!


Similar Posts

Leave a Reply

Your email address will not be published. Required fields are marked *