Every once in awhile you may find that your bike has a fetish for getting close with immovable objects, like trees or rocks, no matter how you try to prevent it. Most of the time this isn’t too big of deal, but occasionally a damaged radiator and subsequent coolant leak will result. This is a big downer. Radiators aren’t cheap to replace! Luckily, some leaks can be repaired if they are small and happen to originate in a favorable location. Not all leaks will be repairable, but once the radiator is leaking there is no harm in finding out if you can repair it yourself.
After inquiring with our subscribers and finding out about some of the questions they wanted answered, the leaking radiator topic came up more than once. Plus I just bought a bike with a leaking radiator which means I’ve got a good example to use. So this week we’ll dedicate some time to discussing our options on how leaking radiators can be repaired.
The two main fixes to repair leaking radiators are to either weld the offending leak or use an epoxy, like JB Weld, to fill the crack or hole. The best solution will be entirely dependent on where the leak is.
The easiest way I’ve found to locate a leak is to submerge the radiator underwater and pressurize it. To do this, all but one of the inlet and outlet holes will need to be sealed off. This can be easily done using tubing and hose clamps to connect the outlets together. Here I’ve used hose from the cooling system and plugged the remaining end with a piece of aluminum.
The two main fixes to repair leaking radiators are to either weld the offending leak or use an epoxy, like JB Weld, to fill the crack or hole. The best solution will be entirely dependent on where the leak is.
The easiest way I’ve found to locate a leak is to submerge the radiator underwater and pressurize it. To do this, all but one of the inlet and outlet holes will need to be sealed off. This can be easily done using tubing and hose clamps to connect the outlets together. Here I’ve used hose from the cooling system and plugged the remaining end with a piece of aluminum.
A long piece of tubing should be connected to the remaining outlet.
Next, we’ll need to submerge the radiator in water. If you have a large utility sink this will make things easy, otherwise a five gallon bucket is your next best option. Submerge the radiator in the sink, then blow through the long hose to pressurize the radiator. You may have to shake the radiator a little bit underwater to dislodge any air bubbles that are stuck between the cooling fins in order to help pinpoint the leak. A steady stream of air bubbles will show precisely where the leak is. You may have to flip the radiator over to find the exact location.
Most leaks originate where the radiator cores connect to the top or bottom of the radiator. These leaks, and any other leaks originating near the cores, won’t be able to be welded because the aluminum is far too thin. In addition, if the leak has come as a result of an object center punching a core, the likelihood of it being fixable is slim. Leaks originating where the aluminum is thicker, usually around the sides of the radiator at the top or bottom, can be carefully welded.
Whenever a leak can be welded I always go for this option before resorting to using epoxy. If you believe the leak can be welded it will be presumed that you either know how to weld or know someone that does that will take the necessary steps to prepare the radiator for welding. In this article, I’m going to focus more on leaks that must be fixed using epoxy.
Once the leak has been pinpointed, carefully clean the area that must be epoxied. After cleaning rough up the surface so that fresh aluminum is exposed. This can be done by using small diamond files or other suitable tools and will help the epoxy stick to the aluminum.
Mix up a small amount of JB Weld or your favorite epoxy and apply a small amount to the cracked area. Once you’ve applied the epoxy use a torch or heat gun to carefully heat the affected area. This will make the epoxy runny and help it fill in the hole. Next, create a vacuum by sucking on the end of the long hose. A MityVac or similar tool is best for doing the sucking. Your lungs can work in a pinch, but the concern here is that any chemical vapors from the epoxy you breathe in won’t be real good for your respiratory system. If necessary, you can omit creating a vacuum and simply rely on gravity to draw the epoxy into the hole.
Once the leak has been pinpointed, carefully clean the area that must be epoxied. After cleaning rough up the surface so that fresh aluminum is exposed. This can be done by using small diamond files or other suitable tools and will help the epoxy stick to the aluminum.
Mix up a small amount of JB Weld or your favorite epoxy and apply a small amount to the cracked area. Once you’ve applied the epoxy use a torch or heat gun to carefully heat the affected area. This will make the epoxy runny and help it fill in the hole. Next, create a vacuum by sucking on the end of the long hose. A MityVac or similar tool is best for doing the sucking. Your lungs can work in a pinch, but the concern here is that any chemical vapors from the epoxy you breathe in won’t be real good for your respiratory system. If necessary, you can omit creating a vacuum and simply rely on gravity to draw the epoxy into the hole.
Allow the epoxy time to cure, follow the instructions on the epoxy you have selected. Then pressurize the radiator underwater and see if the leak has been fixed. With any luck the radiator will be back to usable condition and you can get back to riding!
Leave a comment below if you have any additional tips and tricks for radiator repair!
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