How to Fix a Radiator Leak

Dealing with a radiator leak can be stressful and inconvenient. Your radiator is an essential component of your coolant system. Without a properly functioning radiator, your engine can overheat and become inoperable. Whether you're a seasoned DIY enthusiast or someone who's never popped the hood of their car, fear not – fixing a radiator leak is a task that can be tackled with the right knowledge and a bit of elbow grease. This comprehensive guide will walk you through the step-by-step process of identifying, locating, and repairing a radiator leak. We've got you covered, from the tools you'll need to safety precautions and the various methods available.

Say goodbye to coolant puddles and the worries of an overheating engine as we delve into the essential tips and tricks to fix a radiator leak like a pro.

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Signs of a Radiator Leak

First, it’s important to check for signs of a leaking radiator. A small leak may be difficult to notice at first, but a major leak should be easy to identify. Here are the common signs of a radiator leak to watch out for:

  • Rising temperature gauge
  • Puddles of green or orange coolant under your vehicle
  • Low coolant reservoir
  • Discoloration or rust in your engine bay

A rising temperature gauge is one of the easiest signs to spot. A slightly higher temperature may be caused by other issues or by a minor leak, but if your engine temperature climbs too high you should avoid driving your vehicle. Driving while your temperature gauge is too high could damage your engine and create additional costly repair issues.

Inspect any puddles under your vehicle. One of the most common sources of liquid dripping from your vehicle is your air conditioner. Condensation naturally forms as your AC is operating, so this isn’t a cause for concern. Any yellowish or black colored liquid could be motor oil, and an orange or green color typically indicates a coolant leak.

How to Use Radiator Stop Leak

1. Prepare Your Work Area

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.

2. Finding the Source of a Radiator Leak

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.

3. Seal Your Radiator Leak

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.

Find the Right Parts Today

Once you follow these steps on how to stop radiator fluid from leaking, it’s important to make your way to your nearest AutoZone. All of these solutions may be only temporary solutions, so have a professional inspect your work and determine whether it’s time for a radiator replacement. If the job is too big for you, seek out one of our Preferred Shops to help you do the job.

Advice, how-to guides, and car care information featured on and AutoZone Advice & How-To’s are presented as helpful resources for general maintenance and automotive repairs from a general perspective only and should be used at your own risk. Information is accurate and true to the best of AutoZone’s knowledge, however, there may be omissions, errors or mistakes.

Be sure to consult your owner’s manual, a repair guide, an AutoZoner at a store near you, or a licensed, professional mechanic for vehicle-specific repair information. Refer to the service manual for specific diagnostic, repair and tool information for your particular vehicle. Always chock your wheels prior to lifting a vehicle. Always disconnect the negative battery cable before servicing an electrical application on the vehicle to protect its electrical circuits in the event that a wire is accidentally pierced or grounded. Use caution when working with automotive batteries. Sulfuric acid is caustic and can burn clothing and skin or cause blindness. Always wear gloves and safety glasses and other personal protection equipment, and work in a well-ventilated area. Should electrolyte get on your body or clothing, neutralize it immediately with a solution of baking soda and water. Do not wear ties or loose clothing when working on your vehicle.

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