How to Repair a Radiator Leak

Cooling leaks in cars or trucks are not uncommon and may require you to repair a radiator leak. A dry overflow reservoir, a low coolant level in your radiator, or an overheating engine are often clues that you may have a leak in your cooling system. Often these leaks can be stopped or repaired without having to replace a radiator or having to take your vehicle to a garage. If you can repair a simple leak you can often avoid a more costly repair. If you find a small leak in your radiator and would like to repair it, here are 4 steps that will help you accomplish this repair in just minutes.

Step 1 – Locate the Leak Source

Finding a coolant drip on your driveway or garage floor is only a beginning. It doesn't necessarily mean you have a leaky or damaged radiator that needs professional repair or a replacement. It could also mean you have a leaky hose, a loose drain valve, or a leak in your overflow reservoir. The first thing you need to do is to locate the leak source. This is easy to do. Just look at the bottom of your radiator, radiator hoses, drain valve and reservoir. If the leak is at one of those places you'll easily see a drops of coolant collecting there before it drips onto the surface below it.

Step 2 – Determine the Severity of the Leak

If you see coolant running—rather than slowly dripping—from your cooling system, chances are there is a more severe leak, one that is too big to be repaired by a simple fix. A closer examination of your leak source you should be able to tell if there is a large crack in a hose or in the reservoir, or a very loose drain plug. If the leak is minor and is coming from your radiator, then you can consider your options for stopping the leak.

Step 3 - Using a Commercial Stop-Leak Product

A stop-leak product designed to fill tiny holes in a car's cooling system will often stop a minor, pinpoint leak in a hose, radiator or overflow reservoir. You can buy these products at any auto parts store or most discount stores. Just follow the directions you find on the container. Usually, it consists of simply pouring the contents into your car's radiator. But to avoid getting scalded by hot coolant, be sure the radiator is cool before removing its cap. Some of these products may repair a leak only temporarily, so read about the product, so you don't have unrealistic expectations.

Step 4 – Monitor your Car's Cooling System

Even though your coolant leak may have stopped when you added the stop-leak product, there is always the possibility that a small leak could grow larger. Take care to watch your car's temperature gauge. Especially during hotter summer months. If you see a rise in engine temperature you should check to see if your coolant is low. Occasionally, take time to examine the surface under your car's radiator when it has been parked. If you see evidence of further leaking, you may find it necessary to consult an auto mechanic.