How to Fix a Coolant Leak

Signs of a Coolant Leak

Offered in a spectrum of formulations and colors, the coolant running through your engine’s operating system keeps temperatures regulated. This automotive liquid transfers the heat from inside your engine to your radiator where it is then further dispersed. Coolant is critical for maintaining efficiency and even improving performance. It lubricates the water pump and carries important additives, which prevent corrosion from forming inside the engine.

If your coolant is contaminated, dried up or leaked out, your high-powered engine will ‘melt down’ from extreme heat and pressure. A leaky head gasket means this critical component is warped, which allows coolant to escape into the engine’s combustion chamber. A blown head gasket is just one example of how one damaged automotive part can lead to expensive service repair bills if left unaddressed.

So, what are the signs of a car leaking coolant? If your heater is blowing cool air through the vents, you could have a low coolant problem. When set to heat, your A/C system relies on warm coolant from the engine passing through the heater core. If there isn’t enough liquid circulating, your interior cabin won’t heat up in the winter.

In most modern vehicles, the ‘check coolant level’ warning light will illuminate on your dashboard. For more classic cars and old-school pickups, you should monitor the temperature gauge on your dash to ensure the red needle isn’t steadily rising toward the red danger zone. A clear (or should we say neon) sign that you have a car leaking coolant is orange, green, red or blue liquid forming on the ground beneath your frontend. In a worst-case scenario, you will see visible steam clouds coming from under your hood while your engine is running due to the intense heat radiating from the engine compartment.  

What Causes a Coolant Leak & How to Fix It

Now that you know the signs of a coolant leak, let’s dive into what is likely causing the coolant leak. If you’re lucky, fixing a coolant leak in your sedan, pickup, minivan or SUV is as simple and straightforward as replacing a minor part. A broken radiator cap is one of the quickest fixes any vehicle owner can perform confidently (remember, never open the radiator cap when the engine is hot—always wait until the radiator is cool to the touch). A failed radiator is the most common culprit of engine coolant leaks and often relates back to a broken radiator hose, faulty hose clamp or warped head gasket. A good DIY at-home mechanic can take on the easy challenge of replacing a hose or hose clamp. 

Determining how long it takes to fix a coolant leak greatly depends on finding all the coolant leaks in the radiator, heater core and water pump, as well as hoses and fittings. Hoses and belts need inspected periodically for cracks, tears or weaknesses that might lead to breakage. Hose connection sites must also get inspected for loose fittings and deterioration. If all your engine system components appear in fair condition, it is time to apply leak detection dye for engine coolant. 

Our NAPA experts recommend this one-ounce bottle of LeakFinder Engine Coolant, which is florescent green and brightly indicates when used with a Leak Detection Flashlight designed for tight spaces and elusive leaks. Or, make it easy on yourself, and add a full Leak Detection Kit to your cart. If the leak is specifically coming from the radiator or heater core, follow the instructions on a bottle of liquid Block Seal solution, also called a radiator stop leak or coolant stop leak. The specially formulated additive seals leaks in metal, aluminum, cast, alloy or plastic, thus eliminating any further loss of coolant from the system.

Once you successfully perform a coolant leak fix, don’t forget to top off the reservoir of your engine coolant. Most quality automotive coolants already contain antifreeze and often do not require dilution. Check your owner’s manual for guidance on how to change or fill the antifreeze in your exact vehicle. Be aware, different makes and models require specific formulations. These one-gallon jugs of coolant are designed for heavy-duty fleet vehicles or European and Asian imports. A quality engine coolant from top brands like NAPA, Zerex, Prestone and Peak should last you around 50,000 miles. 

When in Doubt, See the Professionals

NAPAOnline carries all the engine coolant parts and chemicals you need to navigate how to fix a coolant hose leak from an engine coolant pipe O-ring to an engine coolant tube assembly. Shop today for an engine coolant thermostat housing gasket, direct-fit EO replacement coolant temperature sensors and engine coolant level sensors. And don’t forget the coolant test strips that indicate the current freeze/boil point of your coolant.

The most critical aspect of an engine coolant leak (also diagnosed as a radiator coolant leak) is that it you must address it as soon as possible. A busted water pump or damaged heater core needs repaired immediately to avoid disaster. And, replacing these parts requires a certain level of expertise. 

For example, a head gasket is the thin metal piece that separates the combustion chamber from the rest of the engine, which critically helps contain the heat and pressure. Unfortunately, it sits deep in the engine assembly, just under the cylinder head. So, accessing a blown head gasket requires disassembling much of the engine, a process that can easily take an entire day. While the labor cost at an automotive repair center to replace a head gasket can quickly add up to more than $1,000, the equipment and training involved to perform this cumbersome task in your home garage is an even larger investment. When it comes to engine problems, trust the professionals and take your vehicle to a local NAPA AutoCare Center near you.