Valve cores

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mbt
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Valve cores

Post by mbt »

Thought I ask this question here because you people have have always been helpful and know you stuff. What is the primary sealing device for the service ports? I believe that it would be the valve core and it seals and that the service port cap is to protect the core valve from any damage & dirt & moisture etc. That cap would act as a secondary seal if it is is equip with an O-ring or sealing washer if the core had a small leak, it this correct thinking on my part?? Some are telling me the cap is the primary sealing device.
tbirdtbird
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Re: Valve cores

Post by tbirdtbird »

defined however you want, you need both, and the outer cap should have an O-ring

I can unscrew the outer cap on any number of cars that arrive here for a function, and without the outer cap, my sniffer goes wild on most ports. The demonstration is vivid for the car owners since so many ac shops don't bother with the outer caps
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Tim
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Re: Valve cores

Post by Tim »

Combination of both. The cap not going to seal without a valve core. Valve cores tend to leak some.
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Al9
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Re: Valve cores

Post by Al9 »

Once had my variable displacement comp stop going into stroke (cool air only while driving basically) in hot Summer weather about 2 weeks after correcting some minor leaks and RRR recharging by weight. Clutch coil thermal fuse then burned out and had to take it to shop for clutch coil R&R. Half the system charge was inside (hence the early destroke) and tech said the valve core was hissing as soon as he uncapped the LP port.

So both the valve core and the cap definitely work together in sealing the system, but a bad valve core (one that won't seat correctly anymore due to a worn spring, as i found out later; JRA High Flow valve core in my case) will defeat a good cap. That is, the o-ring/seal in the cap can't handle too much leakage.

Good habit to replace cores every time you service the system. I keep a stash since then.

Safe answer, they're both primary sealing devices.
mbt
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Re: Valve cores

Post by mbt »

Thanks for the responses. So as I am understanding the posts made here the cap it to protect the valve core and prevent small leaks that might get passed the valve core but will not hold back the pressure of a complete valve core failure.
Al9
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Re: Valve cores

Post by Al9 »

Exactly that.
philipswanson
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Re: Valve cores

Post by philipswanson »

One thing I know is that many valve cores are damaged during servicing because the service valves are tightened down way too much. I try not to bottom them out all the way. I still have leaks there though.
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JohnHere
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Re: Valve cores

Post by JohnHere »

You have a couple of options in replacing the Schrader valves: Either have the charge recovered, which will allow removal with zero pressure in the system; or use a set of valve-core tools that allow removal while the system is still under pressure. Either way, when you get them out, you can then match them up with suitable replacements.
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