Using Car Air Conditioning Stop Leak

AC vent temperature readingAC Vent Temperature Reading 50 Degrees

Lets discuss the pros and cons of using car air conditioning stop leak. Many people with older rides give up when the AC stops working because these repairs can be so expensive.

In fact, it's not uncommon for a repair estimate to exceed the total value of an older automobile. With that said, you can repair a leaking Schrader valve for under $50.

This is why it's important to find out what's wrong. When you finally do sell your old ride, an operating air conditioning system will increase the value and could close the sale on a hot summer day.

With the low cost of air conditioning stop leak it's tempting to go ahead and throw a can in the system and see if it solves all your problems. In this brief article we're going to discuss the pros and cons of doing so.

If you hunt around on the Internet you'll find people talking about how the stop leak products ruined their AC system. We will tackle this real problem.

More importantly, we're going to talk about inexpensive ways to locate where the Freon is leaking from. Then we'll talk about a commonly overlooked area that’s difficult to check for a refrigerant leak and how to diagnose and fix it without recovering the system.

Car AC Stop Leak

car ac stop leakFJC Car AC Stop Leak Product

As a mechanic, I can tell you that I generally don't believe in any kind of product containing the word stop.

Although there's some science in the product and it can work, I would rather diagnose it and then repair it permanently.

With that said, if the automobile has a slow leak and it happens to be in an area where these stop leak products work well then there's always a chance you could get lucky.

Often this might result in the air conditioning system staying cold for the rest of the summer driving season. To the right you can see a picture of a can of FJC car air conditioning stop leak.

There are a couple of things different about this product that I wanted to highlight as there is no shortage of these types of miracle fluids. The first thing to take notice of is the can is only 4 ounces.

In a lot of cases where you see people talking about how their car air conditioning system was ruined by a stop leak product it's because they installed way too much of it. We'll get into some other problems below, but this is a valid concern.

The stop leak has sticky glue that is supposed to get forced into a small leaking area to seal it up. Most car air conditioning systems have an orifice tube that is by its very definition a small hole that meters Freon.

If you load it up with stop leak and don't run it long enough, you can plug this hole and the air will never get cold until you replace the clogged component. The other thing about the 4 ounce can of FJC car AC stop leak is that it contains a red dye that you don't need a UV detector to see.

I do prefer the UV systems and I will get into that below. But for under $10 you can give a 4 ounce shot of stop leak a try and if you have a leak maybe you can try to find it by searching down the red dye.

Installing FJC Car Air Conditioning Stop Leak

A lot of people say that the 4 ounces is not enough to find a leak. This is a good point. It actually depends on the total capacity of your air conditioning system. The newer systems only hold about a pound and a half of Freon when they're fully charged. In this case 4 ounces is enough.

However, older automobiles can hold as much as 3 pounds of refrigerant when fully charged. Sport-utility vehicles and vans with rear air conditioning systems can hold twice that amount. My point is, find out how much your system holds and if it's more than 32 ounces you might want to get two cans totaling 8 ounces.

Another complaint I see often is that a lot of the dye remains in the can at the end of the charging procedure. You have to shake the can of AC stop leak before and during the charging cycle. You also need to hold the can above the Schrader valve connection to allow gravity to flow the red dye into the system.

It's important to run the air conditioning system on maximum cool for a good 15 minutes or half-hour. You might even want to take the vehicle for a road test to give it an opportunity to distribute evenly.

If you add the car air conditioning stop leak and only run it for a few minutes you do risk plugging the air conditioning orifice tube as discussed above. Also note that when you're dealing with a nearly empty system you might have to add an additional can of regular refrigerant.

These air conditioning systems have pressure sensors that protect the compressor from coming on with a low charge. Adding 4 ounces might not be enough to keep the compressor clutch engaged. This depends on how much Freon leaked out.

Problems with Installing Car AC Stop Leak

Although there is a chance that everything could go your way and that this one single can could solve all your problems it's not likely to happen that way. The can says it includes an O-ring seal conditioner.

In my professional opinion, when I find an air conditioning system leak on a car, it’s from an O-ring connection more than 50 percent of the time. What happens is these joints loosen up and flex. They can cut, wear or damaged the O-ring. And the only way to fix it is to recover the refrigerant and replace that damaged O-ring.

Thinking that a magical additive in a car air conditioning stop leak product will renew your O-ring good enough to seal the leak is a stretch. The most common problem with installing a single 4 ounce can of stop leak is it won't work. If you install too much stop leak or you do not allow it to distribute evenly throughout the system it could clog individual components.

There is another situation to discuss before we move on. If you overcharge the system in an attempt to work more stop leak into the refrigerant you could do a lot of damage. A further explanation is that when you overcharge a system you can force liquid refrigerant into the compressor inlet.

This will destroy a healthy air conditioning compressor because you can't compress a liquid. There’s usually a buzzing sound from the compressor before it actually self destructs.

If you turn it off soon enough maybe you can save yourself from creating the worst air conditioning problem an automobile can have. The other thing I've seen people do is overcharge it to the point where the high pressure blow off valve allows the overcharge to escape into the atmosphere.

Venting refrigerant is bad for the environment and it's not good for humans either. Refrigerant can cause skin damage in the form of frostbite, but it can also cause permanent blindness if you get it in your eyes. As a professional I can tell you that I will not approach a car air conditioning system without safety glasses and work gloves and neither should you.

My final thoughts on installing a stop leak product designed for a car air conditioning system is you probably shouldn't do it at all. The reason I say this is because the total amount of refrigerant in the system is critical to its ultimate performance.

The only way to be sure you have the right amount in there is to remove it and weigh it. You need a charging station to do this. This brings us to the right way to stop an automotive air conditioning refrigerant leak.

The Right Way to Stop a Car AC Freon Leak

master cool refrigerant leak detectorMastercool Florescent Dye Refrigerant Leak Detector Kit

On the right you see a picture of the master cool professional grade refrigerant leak detection system. This is a UV type leak detector.

Note that you can also use it on other automotive systems as long as the fluid contains the fluorescent dye designed to operate in that system.

Although this professional system costs a little more it does work well and it comes with everything you need in a handy storage box.

The key component is the AC dye injector that's used in automotive air conditioning systems. Professionals will first recover all refrigerant and store it for reinstallation.

Next, you remove the Schrader valve and physically pump in the right amount of fluorescent dye into the system. This is another area where you don't want to install more than is recommended.

Although it's not as sensitive as the leak sealing products it can change the cooling characteristics of the refrigerant if you install way too much. After the injection is complete, we install a full charge of Freon.

Next we kick the system on by engaging the compressor and circulate that fluorescent dye. I'm one of those mechanics that believe it's necessary to take the vehicle on a road test with a lot of twists and turns so that the liquid dye can slosh around in all of the corners of the system.

When you return from the road test you can pull out the specialized glasses and the black light that triggers the illumination of the crystals in the fluorescent dye. These systems work well at all levels of natural light. However, the darkness of an enclosed area like a garage makes the leak even easier to detect.

An Often Overlooked Car AC Freon Leak Area

automotive AC Schrader valveAutomotive Air Conditioning Schrader Valve

The Schrader valve is a patented device with a spring-loaded seal that allows us to add refrigerant, stop leak and detection dye to the system without losing any of the Freon to the atmosphere. It's an amazing little device that’s also used to hold the air pressure inside your tires.

This is often an overlooked area where Freon can leak out of your car. The device can loosen up and leak tiny amounts of Freon over long periods of time. Using the leak detection methods discussed on this page doesn't work for the AC Schrader valve.

When you install the dye you will get some of that liquid on the Schrader valve so it will always indicate a leak. Not only can it loosen up over time, but systems that get a lot of maintenance or had a lot of problems can wear out the rubber O-ring seals on the Schrader valve.

A lot of times when mechanics say they can't find the leak it’s because they didn't check the air conditioning Schrader valve with a halogen Freon leak detector. This is a sniffing device that sounds an alarm when it senses different types of refrigerant. Since Freon is heavier than air you actually have to place the sensing probe below the Schrader valve not above it.

Unfortunately this is not a do-it-yourself repair unless you get the special tool from master cool. You can't just remove the Schrader valve because all of the refrigerant will vent into the atmosphere. This means you’ll have to recover all of the Freon before you replace the Schrader valve. The master cool special tool allows you to replace the Schrader valve without losing any refrigerant. This thing is available below for around 36 bucks.

Head back to the AC start page and learn more about how to fix the air conditioning on your old ride.