Will Freon Leak Without A Schrader Cap?


Service ports are where technicians attach their gauges that measure the pressures in an air conditioner or heat pump.

Schrader core valves that are inside these service ports can leak, even with a schrader valve cap. A simple way how to tell if a schrader is leaking is to spray it with diluted dish soap. It’s not a guarantee you’ll see a leak for a couple of reasons.

  1. The refrigerant may have already leaked out.
  2. The leak is too small for soap bubbles and requires a refrigerant leak detector.

It’s hard to say why a particular schrader valve may leak. It may be due to a defect, a tiny piece of debris, or a worn out seal because of too many uses and time on the job.

Who knows, it’s such a small device and not worth the forensics to determine it’s cause of death. It’s kind of funny how such a small insignificant looking piece of metal, gasket, and spring can hold back such high pressure.

Then again it’s not so funny when they fail and you lose all that Freon.

A cap with schrader valve can stop the valve from leaking. There is more than one type of cap and further down in this article I’ll discuss the types of caps and which one is best to stop the valve from leaking.

I’ll also show you how a leaking schrader valve core can be changed without even losing the Freon (brand name) charge in your system.

Not that I would advise that you do that, but just so that you know it can be done is worth while. It can be very hazardous and expensive if not done by someone with the skill and experience required to do so in a safe manner.

The chance of losing your complete charge of Freon (sense Freon is a brand name I will often refer to it as refrigerant)

Below is a picture of the service valves on a heat pump. The only difference between service valves on a heat pump and service valves on an air conditioner is that most heat pumps have three or even more service taps where most air conditioners have only two ports.

Notice the three black caps. They are locking caps that require a special tool to remove.

What that boils down to is that heat pumps have more potential for leaks. What you see above is three schrader valve locking caps. The reason there are three is because in a heat pump the two copper lines change purpose from heating to cooling.

The third service port is a constant low pressure side of the compressor. The insulated line will be low pressure in cooling mode and high pressure in the heating mode.

With the newer refrigerants the pressures are much higher and the potential for leaks is even greater. Pressures inside air conditioners and heat pump with the new save the planet R410A will go up around the 400 pound range.

What Is The Best Type Of Schrader Cap To Use?

By far the best cap to use would be a schrader valve locking cap. In many areas of the country they have become required to be installed at the time of installation of new equipment.

The four caps below would be what you’d need if you have a heat pump. If not then look around on Amazon’s site and you may find a set of two with a key. Don’t forget the key. You can click on the image to see the ones I selected or go here to see a broader selection.

You can pick a color specific locking cap that represents the type of refrigerant in your system or you can go with the gender neutral selection for reasons of your own.

You can find the type of refrigerant your system contains by looking on the manufacturers label on you outdoor unit. Sometimes you have to almost stand on your head to find it, but it’s there.

There are some labels that have lost there identity. The weather has eroded them so bad beyond readability. In that case it’s probably the old R22 or the green locking cap. If you can’t decide it’s perfectly okay to go with the gender neutral.

Newer units would contain the R410 refrigerant. Pink would be the color of choice for that gender. Of course, you can still choose to be obstinate and pick whatever.

The reason for the locking covers is kind of important. It seems that it has become a craze to either steal refrigerant or inhale it in an effort to get high. A serious problem that has been labeled huffing. Don’t get any ideas.

These caps can possibly stop a small leak from a bad schrader valve. But it’s best to change out the core and have a good schrader core and cap.

My son works for a company in Alabama and he told me recently that all the techs and installers in the company where he works are required to switch out the plastic schrader caps that are on any of the equipment they work on to the brass caps like the one pictured at the top of this article.

How To Remove A Schrader Core Under Pressure

Every technician who has had any experience at all has come across a leaking schrader core. A technician attaches service gauges to the unit and when the gauges are disconnected the schrader won’t stop leaking.

At which point the technician reaches into a bag of tools and pulls out one of these:

Schrader core removal tool

Without going into too much detail this allows the tech to pull out the defective schrader core and insert a new one without losing any refrigerant.

Some techs use this tool to remove the core for purposes of evacuating the system. With the core out of the line it clears the way for a more efficient and quicker vacuum.

I’ve inserted a video here in case you really want to see how these work.

Chad Peterson

Chad Peterson is near 40 year veteran of the HVAC industry. "I like to explain heating and air conditioning problems in a way the average home owner can understand. "

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