I tried a little bit of everything to solve this. Turns out it was the grey gas fitting. I replaced the fitting and put a bit of lube on the o-ring and it held pressure. I did try flipping it over, but since the keg was cold all the condensation ran down and I couldn't tell what was making what wet.
No I can't hear anything, it's an incredibly slow leak. I can only tell by checking my gas pressure after an hour. I'd like to pressurize it and put it in a tub of water, but I don't want to lose the beer inside. I'll try the keg lube on the o-rings
I've just put 5 gal of IPA into a corny keg and noticed it is leaking CO2. I've tried the soapy water test, but can't find any bubbles. Any ideas for troubleshooting? I'd like to save the beer if possible.
Sorry if people have asked this before but how do you measure the temperature of your Mash? Are your thermometers calibrated? Compensated for altitude?