Seal It and Forget It: How to Identify a Coolant Leak in Your Car and Seal It Like a Pro

Your car’s radiator keeps the engine purring at the right temperature. But a coolant leak is a problem. Here’s how to identify a leak and seal it like a pro.

It’s easy to take your ride for granted. You get in, turn the key and go. Throw a quart of oil in now and then and you figure your maintenance program is complete.

Until the day you’re sitting at a red light performing car karaoke and notice smoke pouring out from under the hood. 

Either your radiator randomly sprung a leak or maybe it’s been slowly leaking coolant for weeks and you had no clue. So you sit there, hands frozen on the wheel and wonder if you should keep driving or phone a friend.

We can’t tow your ride, but we can help you figure out the problem.

Read our definitive guide on detecting and sealing coolant leaks in your car. Hint: Sometimes your car gives you clues before the engine overheats.

Watch the Gauges

If you don’t pay attention to any other gauge on your dashboard at least pay attention to your temperature gauge.

The first clue of a problem with the cooling system often comes from the temperature gauge. A high temperature gauge reading could indicate a loss of coolant.

Never ignore a high temperature gauge reading because it could mean your engine is overheating. And overheating engine usually leads to a towing charge.

In newer model cars, the check engine light may also be an early indicator of a cooling system problem. Pay attention when it comes on and then take the car to a mechanic, so you can have the error codes read.

The temperature gauge is relatively reliable as far as warning you of a possible leak. Be aware there are other reasons why a gauge gives a hot (or cold) reading that has nothing to do directly with a coolant leak.

A puddle under the car should be your next clue.

Don’t Ignore Puddles

If you’ve ever noticed a puddle of fluorescent green or orange fluid under a car, you’ve seen coolant.

You assume if the puddle isn’t large, you’re fine. Wrong. Anytime you see coolant under your car, it’s a bad sign.

The cooling system is a closed system and while it allows for evaporation, if you see coolant on the ground, you have a leak.

Now don’t panic every time you see a puddle under your car. When you run your AC you’ll see condensation in the form of a puddle. It could also be from a car belonging to another driver.

The smart thing to do if you notice a puddle is to check your coolant reservoir.

Check Your Coolant

If you weren’t aware, the coolant reservoir is not your radiator but it is a vital part of the cooling system.

The coolant reservoir stores excess coolant fluid until it’s needed. If you’re not sure where it’s located, find your radiator hose. Follow it from the radiator to the reservoir.

Voila! It’s a plastic receptacle and usually has a low and a high fill mark. Your coolant reservoir is also the first place you’ll be able to notice a leak.

If you have a coolant leak the level in the reservoir won’t get to the high fill mark, even when the vehicle is warm. If you notice low levels of coolant in the reservoir, take a minute and top it off before driving.

Check Your Hoses

If you’re even more convinced you have a leak, check your hoses. Hoses are the number one cause of coolant leaks.

Most vehicle cooling systems have 4 main hoses:

· Upper radiator hose
· Lower radiator hose 
· Heater hose (2)

If you detect a leak in any of the cooling system hoses, you’re in luck. They don’t cost much to replace and you can probably switch the culprit out by yourself. If the hoses look good, move on to the radiator.

Inspect the Radiator

So far, you’ve checked your coolant, watched for puddles of fluid under the car, and checked out the hoses. Now it’s time to get up close and personal with your radiator.

The simplest test for a leak in or near the radiator is the cardboard test.

Place a piece of cardboard under your car and check it in the morning. If the leak is in the radiator, you’ll see coolant on the cardboard.

The outside appearance of the radiator often tells the story as well.

If there’s a coolant leak, coolant and water escaping from the radiator can cause rust development. If you find rust spots, check also for visible signs of radiator fluid.

Mystery Solved

If you’re fortunate enough to find a leak without any further testing, you can move on to the next step.

But first, aren’t you curious why a radiator springs a leak? Look where it’s located—at the front of your vehicle. The radiator takes a beating from rocks and other debris you pick up on the road.

Also, if you don’t flush it on a regular basis, it can develop corrosion from sludge build-up. Corossion often leads to coolant leaks.

A leaky radiator allows draining of your coolant to the point where your engine overheats. The good news? All it takes to avoid a costly engine repair is to plug up the leaks with a radiator stop leak product.

It’s Not the Radiator

If your radiator seems fine, consider the engine block. The engine block can develop small cracks, which allow a coolant leak.

You may feel like Sherlock Holmes at this point, but persistence pays off and can save you from a major repair bill.

If you think you could have a leak from the engine block, try a cooling system sealer before you go into an all-out panic. Cooling system sealers act like little detectives. They flow through the cooling system until they discover the leak or leaks. If you have multiple cracks in the cooling system, the sealer fills all of them in.

It’s quick and gets your car back on the road—probably for many more years.

Coolant Leaks Aren’t the End of the World

They can be hard to track down but if you’re diligent, you’ll eventually find a coolant leak. 

Most drivers panic when they see coolant on the ground or have an engine light ringing the alarm. Remain calm and go through the steps listed above.

Once you narrow down the leak, seal it up and forget it.

For more information on all of our cooling system products, click here.

What is the Best Cooling System Sealer?

There are many cooling system sealers to choose from but this one lays down a thin coating over all the cooling system surfaces.

Unlike a typical radiator stop leak product, a cooling system sealer works to fully coat and seal your cooling system all over. This kind of technology has been around since the 50’s or maybe even longer.

One such product like this that is still readily available is Irontite Ceramic Motor Seal. Sometimes referred to as “liquid glass” this is used to coat the walls of the cooling system.

Filling in cracks and metal porosity making a “smooth as glass” coating that not only seals but also promote better coolant flow. Better flow means better cooling. Sometimes as much as 15% better cooling ability.

Designed for the Engine Rebuilder

Ceramic Motor Seal was originally designed with the engine rebuilding in mind. After rebuilding an engine there could be areas where the cooling system may weep around replacement sleeves or bearings.

Also, there could be minor cracks from the fatigue of the casting. Minor in that they don’t cause a structural problem, but could allow for coolant seepage and added turbulence to the flow of coolant.

Made for the Professionals

Marketed to the Engine Rebuilder Professional along with an external circulating pump that both pumped and heated the Ceramic Motor Seal solution, Irontite had solved a troubling problem that rebuilders had been struggling with.

Now, after a rebuild the block and head could be pressure tested and if they failed that test the rebuilder could circulate heated Ceramic Motor Seal and get the pressure test to pass with flying colors.

This proved to be a very successful solution to a nagging problem.

It can Repair a Coolant Leak

Many years later it was discovered that Ceramic Motor Seal could be used to repair a coolant leak in an engine that was in chassis.

Just by removing the engine anti-freeze and adding the Ceramic Motor Seal solution and running the vehicle for several hours the same benefits could be given to that in-chassis motor.

Sealing of a leak, but also the added cooling benefits of a fully coated cooling system.

How does it work?

Unlike a typical radiator stop leak product Ceramic Motor Seal must be used with caution or you could cause very real and expensive damage to a vehicle.

First of all, Ceramic Motor Seal is not compatible with Anti-Freeze. If you pour it into an anti-freeze mixture it will turn to goo and eventually into stone.

And if you spill any on painted or chrome surfaces it will damage them if it dries.

When you circulate the Ceramic Motor Seal solution with heat it very slowly accumulates at an almost microscopic level to all the surfaces it contacts.

Given enough time it forms a smooth surface over everything. You then drain it from the system and rinse with water to get all non-accumulated solution out of the system.

Then you leave it open to the air so that it can cure. 24 to 48 hours of air dry cure time is recommended.

Now the process is complete and you can add your normal anti-freeze mixture into the system.

We further recommend adding All Weather Seal as a preventive against any future leaks.

Also, before you start the process it’s a good idea to flush your system with our Irontite Thoro-Flush product.

Just so you have good clean surfaces for the Ceramic Motor Seal to bond to.

The Best Radiator Stop Leak

I know that is a pretty bold statement. But after over 60 years of use mostly by industry professionals and still selling strong, I think it’s pretty safe to say.

Radiator Stop Leak products and their like have been around ever since there have been radiators. We’ve all heard the stories of how you can use Black Pepper, or raw egg whites to seal a leak. And unfortunately, there are some commercial products on the market that aren’t much better than those old home remedies to fixing a leak.

Stop Leak Designed to Work

All Weather Seal from Irontite Products is different. And I’m going to tell you how and why it’s different in this article. It has some unique properties that almost none of the other products on the market have.

  • It blends with your existing Anti-freeze forming a microemulsion
  • It is so small when blended that if we didn’t color it you wouldn’t know it’s there.
  • It only works where the leak is. No fear of plugging heater cores, etc.
  • It can be used as a preventative to keep vehicles in service
  • It works FAST! Within 10 min. of reaching operating temperature your leak will stop
  • It work regardless of what material the leak is in. Rubber, Iron, Aluminum, Plastic, etc., it doesn’t matter.
  • It is compatible with all the different kinds of anti-freeze products on the market today. Even the waterless anti-freeze and extended life versions.

Are you impressed yet? I know I am. Those are some pretty significant things and it’s likely you won’t find any other radiator stop leak product that can boast all of those points.

Back in the day when Irontite Products enlisted a chemist from UCLA to engineer All Weather Seal, these were all the things we wanted it to be able to do.

And the results were just what you get today. With a proven 60 year history of stopping most any kind of leak you can imagine. There are only 2 things that stop All Weather Seal from doing its job. Either the leak is just too massive or due to air pressure or moving parts it can’t stay patched.


It blends with your existing Anti-freeze

In the bottle, All Weather Seal is concentrated. One bottle (16 oz) treats up to a 6-gallon capacity cooling system.

Adding more is not necessarily beneficial. So if you have a 3-gallon system then you only need use half the bottle.

It’s very critical that you get it blended in with your cooling mixture. So be sure to add it in where circulation of the coolant is happening as soon as possible.

Once blended it would be undetectable if it weren’t for the fact that we add black pigment to it so you can tell something is there beyond just your anti-freeze mixture.

Similar to how instant coffee mixes with water and after mixing stays mixed. There is no “settling” of All Weather Seal once it is properly mixed. That is what a microemulsion is.


It only works where the leak is

Once fully mixed All Weather Seal is dormant until 2 conditions are met.

Condition one is the mixture must be at or near your engine operating temperature.

Condition two is the mixture must encounter air of a lower temperature.

When those two things happen All Weather Seal “wakes up” and starts to form a patch over the area where it is encountering the air. Similar to how a Beaver builds a dam.

And once the leak is stopped then also the action of patching goes back to being dormant and looking for the next area of escaping coolant.

And should a previously patched leak start leaking again, All Weather Seal will go to work on it again.


It Will Prevent Coolant Leaks

Many users and believers of All Weather Seal find it very useful as a preventive measure.

Fleet owners and commercial industrial equipment owners automatically add All Weather Seal to new vehicles in their fleets to help prevent any down time of the vehicle.

Over the road truck drivers keep a bottle or two around or just add it in after any coolant service.

It makes sense if you have an end loader out in the field doing work and some debris causes a small leak in the radiator or a hose clamp becomes a little loose and starts leaking.

Without All Weather Seal that vehicle may have to stop work before it’s done with the job in order to be serviced.

But with All Weather Seal in the system the leak is patched and the vehicle continues working.

This same principal applies to all kinds of different commercial settings. Rental Car companies, used car dealers, fleet trucking, etc.


It Works Regardless of What Material is Leaking

I frequently get asked if All Weather Seal will work with Aluminum engines or radiators with plastic tanks.

The answer is a resounding YES! It really doesn’t care what the material is.

It just wants to plug that leak as fast as it can and be done.

One little sidebar about radiators with plastic tanks. Plastic weakens with age. If your older vehicle with plastic tanks has had a small leak for a long time, that leak has allowed your cooling system to NOT become fully pressurized.

If you treat that vehicle with All Weather Seal. When it seals the leak and your cooling system is able to get up to it’s normal pressure level the plastic may be too weak to handle that normal pressure and burst or crack.

So be warned, this is not the fault of All Weather Seal, this is old plastic not able to function at normal pressures anymore.


Compatible with All Kinds of Anti-Freeze

As of this writing, over the past 60 years of use, there have been no reports of any incompatibilities with All Weather Seal and any antifreeze mixtures in use.

And we have had some reports from customers who tried it with some very unique cooling system solutions and were so happy that it worked they called in to tells us all about it.

All Weather Seal is made with mostly inert materials that won’t react with other chemicals. It just happily tags along suspended in solution looking for a leak to cover up.

Where Can I get All Weather Seal by Irontite?

Irontite Additives are available from most major parts stores in the U.S. and Canada. It is quickly expanding into Mexico.

You may not see it sitting on the shelf in your local parts store because shelf space is not only very competitive but in some cases, the store managers can determine what products to keep “in stock” and on the shelf.

But if you ask for it at the parts counter they will be able to get it from their main warehouse. Usually, they can get it by the next business day for you.

Be sure they spell Irontite correctly or give them the part number of 468-9130-16. A list of many store brands that carry it can be found on the Irontite Website here.

You can also purchase a bottle from Amazon if you prefer.

And if you have a small store or are a mechanic who wants to have it available for customers you can get volume discount pricing direct from Irontite Products.

Just call them up during normal business hours and choose the Parts Sales department to speak to a salesperson.