How to Fix a Radiator Leak

Before you learn how to use radiator stop leak, you need to find the source of the leak. There are many areas of your radiator that could be cracked, so finding the leak can take some time.

Park your vehicle and wait for the engine to completely cool. Open the hood and wait up to a few hours before the engine is fully cooled. Radiators are pressurized systems, so be extremely cautious before opening your system or working in your engine compartment.

Use safety gear to ensure a safe maintenance routine. Safety glasses and gloves are recommended for safe inspection and repair. To spot a leak, it’s best to first clean your radiator and surrounding components. Use a hose to clear off your radiator. Avoid wiping any part of the radiator as this could cause further damage to the fragile cooling fins of the radiator.

Once your radiator is clean, check for any signs of cracks or leaks. A visual check of much the radiator may be difficult as it is located typically behind your air conditioning condenser and partly covered by a fan shroud. As best you can, inspect the radiator, the end tanks, reservoir, and any surrounding tubing. If you don’t immediately see any leaks, turn on your engine and inspect your engine compartment.

A leaking radiator may be hissing, dripping or spraying coolant. You may have to inspect your radiator on all sides to find the source of the leak. Be cautious when looking under your vehicle, as your radiator leak may be spraying hot radiator fluid.

For a professional test, purchase a coolant system pressure tester. These convenient testers are secured on either the radiator or pressure cap spout and create a seal. Be sure to follow the instructions accompanying the tester ensuring the system without pressure before removing radiator cap. Once sealed, it pumps 10 pounds of pressure into the system. Check if your radiator is capable of sustaining 10 pounds of pressure. If the pressure drops, look for the source of the air leak.

Don’t use more than 10 or 15 pounds of pressure, otherwise you could damage your radiator and cause even more leaks. Your coolant system is typically only rated for 15 pounds, so any more pressure could have adverse effects.

There are a few common ways to fix your radiator. Depending on the situation you’re in, you can use either emergency fixes or commercial products. Using a commercial product, like Bar’s Leaks, offers a more reliable seal and avoids any additional damage to your vehicle, but there are a few household items you can use to fix your radiator temporarily in case of an emergency.

First, an easy solution for most leaks is commercial leak sealant. While this sealant isn’t as effective as the professional repair solution, it provides you with a reliable seal as you make your way to your local auto parts store or mechanic:

• Once your engine is cool, pour your sealant directly into your cooling system
• Top off your radiator with coolant and water and seal your system
• Run your engine for approximately 10 minutes and then let it sit overnight
• Turn your engine on again to see if it has properly sealed

Another solution is to use radiator epoxy. Once you’ve found a visible crack, clean the area thoroughly with brake cleaner exercising caution not to damage anything in the surrounding area. Once the area is completely dry, work your epoxy into a malleable putty and create a coat at least an eighth of an inch thick. Let it sit overnight and turn your engine on to test the seal.