I'm still learning Automotive A/C repair and I've done some checks on various vehicles and noticed that most of them don't have a schrader valve inside the high side port. They have a tiny black rubber plunger inside the port and often enough they leak. The port cap seems to prevent them from leakin...

Thanks brother....that's good to know.

It's been years since I posted on this forum and had to re-register to the newer forum. Anyhow my question has to do with buying this brand new tank cylinder so I can use it for nitrogen, https://www.harborfreight.com/welding/welding-accessories/20-cubic-ft-argon-gas-cylinder-92807.html It's markete...