Rick's Free Auto Repair Advice

Does AC stop leak sealer work?

Can you fix your AC system with AC stop leak sealer?

How does AC stop leak sealer work?

AC stop leak sealer is not a new product. It’s been used in the natural gas industry for decades to seal small leaks on pipelines. The sealers are sold as just a leak sealer or as a combination leak sealer and seal conditioner. It’s also included in many AC recharge kits as an added selling feature.

When sold as just a leak sealer, the product is injected into the AC system as a liquid and remains a liquid until it reaches a leak area. As the refrigerant leaks out of the system, the expanding refrigerant removes heat, creating a cold spot that then causes moisture in the air to condense. It’s that moisture that interacts with the sealer to form an epoxy-like “scab” to seal the leak.

When the sealer is a combination sealer and conditioner, the product contains a seal swelling agent to soften and swell O-rings located in hose connections.

Sounds good so far, right?

Unfortunately, ac leak sealer can’t distinguish between water that’s condensed at a leak location and water that’s already in the system. It’s important to understand that a leaking AC system has already let outside air into the system and that air contains moisture. In most cases, that humidity is absorbed by the desiccant in the receiver/drier or accumulator. If there’s any free-flowing moisture in the system, it’s usually at the orifice tube or expansion valve, since those are the areas where there’s a temperature drop and condensation. And THAT is where the problem arises. Like I said, the sealer can’t tell the difference between leak water and desiccant water. So it will react and harden WHEREVER it comes in contact with water.

AC stop leak sealer can clog orifice tubes, expansion valves, receiver drier and accumulator

Adding leak sealer to a “wet” system can cause far worse problems than the

clogged expansion valve

Clogged expansion valve

original leak. That’s why the instructions for the professional AC leak sealers require a complete system evacuation to dry out the system. Some even require a new receiver drier or accumulator before adding the sealer. If you just add AC sealer to a wet system, don’t be surprised when it makes things worse.

AC leak sealers can affect cooling performance

This one is a mixed bag. If the sealer works to seal small leaks in the condenser or evaporator that automatically means it’s improving system performance. No leaks = better performance. BUT, since the leak sealer isn’t a refrigerant, so it doesn’t provide any cooling effect as it travels through the orifice tube or expansion valve. In other words, if you evacuate the system to dry it out, and then add leak sealer and refrigerant, the combination can reduce cooling by up to 7%.

AC leak sealers can’t seal many leaks

When the sealer interacts with moisture it forms a hard seal. That’s great

comprssor shaft seal

Compressor shaft seal

for pinhole leaks in the evaporator or condenser. But it won’t stop leaks at seals around rotating parts or at rubber O-rings, hose fitting or the compressor shaft seal—which, ironically, are the most common sources for leaks.

AC stop leak sealers cause other problems,

Here’s an exact quote from industry trade magazine MOTOR from its April 2003 issue

“Pinhole sealing is a valuable function. But there’s no evidence that stop leak will seal anything else with any reliability, whether it’s cracked welds or a bad compressor shaft seal, or even severe pinhole leakage from the evaporator. Because the sealer works by reacting with

moisture in ambient air, it also can produce clumps that restrict refrigerant flow, if there’s enough moisture in the system. In addition, the seal sweller in some sealing products could distort some O-ring materials.”

Worse yet, manufacturers of refrigerant recycling machines are reporting problems with refrigerant recovery when a customer has used an AC leak sealer product in the system. The sealer can plug the solenoid

ac leak sealer

Clog in recycling machine equipment caused by leak sealer

valve in the recovery equipment and also damage the seals in the equipment. Recover machine manufacturers like Skye, RTI, Visteon, Ford, Delphi Harrison, Four Seasons and NAPA will void the warranty on the equipment if they find any evidence of AC leak sealer.

Recovery machine manufacturers respond to the problems

To prevent damage to the machines, shops must install a separator/filter to prevent the leak sealer from entering the recovery equipment. The filters remove sealer clumps, oil, dye and seal swellers. These filters must be replaced on a regular basis to allow the recovery equipment to work properly

Here’s what you can expect if you use an AC leak sealer

• The sealer will probably work for very small pinhole leaks in the evaporator or condenser

• It will not work for leaks at the compressor shaft seal or O-rings.

• It will clog the desiccant in the receiver drier or accumulator if the system contains moisture

• It will reduce cooling by up to 7%

• If you ever take the vehicle to a repair shop, you will incur addition costs to evacuate the system because it is contaminated with sealer.

The most effective way to use AC leak sealer

To get the greatest benefit from a leak sealer you must fully evacuate the system and replace the receiver/drier or accumulator. Then pull a vacuum to remove any remaining moisture before refilling with refrigerant and leak sealer.

©, 2018 Rick Muscoplat


Posted on by Rick Muscoplat


Custom Wordpress Website created by Wizzy Wig Web Design, Minneapolis MN