How to stop Radiator Leak

Locate the leak. Sometimes, you can see steam coming up from the radiator, indicating a pinhole or ruptured seam. Otherwise, wash down the radiator and the hoses with water and start the engine again; as it runs, watch for the leak.


Let the engine cool off. Once you've found the leak, wait a few minutes to take off the radiator cap; otherwise, you could be scalded by hot water or steam.

Plug the leak. Keep in mind that these are temporary fixes and are not meant to be substitutes for a permanent fix - they're meant only to get you to a repair shop. You have a few options; use what you have on hand or can attain most easily:

• Use cold weld epoxy. This is the safest and most reliable option, but it might be hard to find if you suddenly break down. To do this, make sure you have water on-hand before you drain the radiator. After it's dry, apply the cold weld epoxy over the leak. This method will require waiting about two hours for the epoxy to dry.
• Use an egg. One or two eggs will temporarily stop the leak by cooking in the hot water of the radiator. The pressure of the radiator will force it into the leak (if the leak is in the radiator itself and not one of the hoses).
• Use black pepper. Pour a spice-rack-sized container of pepper into the radiator. It will flow to the split or pinhole and will harden like a rock and plug the hole. If you don't have pepper, paprika, cornmeal and mustard powder are acceptable alternatives.
• Purchase a commercial leak repair product. These are widely available in most automotive parts and supply stores. Use these as a last resort; it should be noted that adding any of these types of products to the cooling system of your car can obstruct the flow of water through the radiator, and potentially damage other parts of your car such as plugging the heater core.
• Weld the leak. If you have the expertise and the equipment, you can try to remove the radiator from the car and weld the leak yourself.
• Use duct tape. If the leak is in only on one of the hoses, you can wrap duct tape around it for a temporary fix until you can purchase and install a replacement hose.

Build a vacuum. Remember to install the radiator cap so pressure will build and force the epoxy, pepper or egg into the leak.

Get to a repair shop. A leaky radiator will require a more permanent fix than those listed above. Any additives may be flushed out by high pressure later when a permanent professional repair is made.

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• How to stop Radiator Leak

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