Leaky AC Schrader

[JHZR2]

My 82 Mercedes ran R-12 when I got it, and never required top ups for years. It sat for ~6 years, and the charge came out I'm trying to chase down leaks, and one spot I found a potential was the actual schrader valve. I replaced it, used some R-12 Nylog on the threads, and put the new schrader in. Pressurized the system with non-CFC gas as allowed by the EPA, and I see some slow bubbles in the tiny bit of oil sitting in there. This seems unacceptable. I have good metal caps with new o rings, as I've read in the past that the schrader valves aren't really a perfect seal on AC systems. But I'd assume that was relative to slow diffusion, and maybe the higher pressure on the high pressure side. My high side one seems to check out. Fortunately it seems to be the low side, which is front and center in the bay, which might be suspect. Any thoughts? Schrader replacement was new stock. Thanks!

 

[Avery4]

Schrader valves never make a perfect seal from my experience, that's why all the caps have O rings in them. Even the schrader valve in my new OEM Honda low pressure AC line doesn't seal perfectly. If the leak is excessive it may have a piece of debris stuck in it, you could try pushing it in for a split second with a screwdriver to try to blow the debris out and get a better seal. "Slow bubbles" doesn't sound excessive or abnormal to me. Other than that I would just put a good cap on it and call it good if it was mine

 

[EA82]

Try loosening it a bit and re tighten it or just push the pin for a split second, this usually works for me with schrader cores on residential units.

 

[Jetronic]

you waited for the gas mixed in the oil to evaporate, right?

 

[JHZR2]

Originally Posted by Jetronic

you waited for the gas mixed in the oil to evaporate, right?

The gas was put in a week prior to doing this...

 

[Jetronic]

yeah shouldnt bubble then. I'v just used some valves from tire valve stems in the past and always had success. It really is down to the specific valve construction though, some are prone to leaking. But when used in a tyre they also experience centrifugal forces which promotes bad sealing. Have a look at some valves and try one with a different construction.

 

[TurboTravis]

I recently learned that there are a lot of different styles of schrader valves (some look very similar), and of varying quality.

 

[WyrTwister]

Originally Posted by JHZR2

My 82 Mercedes ran R-12 when I got it, and never required top ups for years. It sat for ~6 years, and the charge came out I'm trying to chase down leaks, and one spot I found a potential was the actual schrader valve. I replaced it, used some R-12 Nylog on the threads, and put the new schrader in. Pressurized the system with non-CFC gas as allowed by the EPA, and I see some slow bubbles in the tiny bit of oil sitting in there. This seems unacceptable. I have good metal caps with new o rings, as I've read in the past that the schrader valves aren't really a perfect seal on AC systems. But I'd assume that was relative to slow diffusion, and maybe the higher pressure on the high pressure side. My high side one seems to check out. Fortunately it seems to be the low side, which is front and center in the bay, which might be suspect. Any thoughts? Schrader replacement was new stock. Thanks!

Try Schrader valves sourced from a refrigeration / HVAC supply store ?