Found Walk-In Freezer system low on refrigerant so I looked for leaks. Initially I couldn't find anything leaking so I boosted the system pressure with nitrogen. I could then hear the valve on the receiver leaking. I put thread sealant on the valve caps and tightened them which should be fine until I can get a new receiver. I also noticed the suction service valve on the compressor is badly rusted and is a risk of a future leak. I will order the receiver, valve and new dial thermometer (per Sandy's request). I added refrigerant and temp is now dropping. 10/24/19 Recovered refrigerant and replaced the leaking receiver and suction service valve. I changed the filter drier and pressurized system with nitrogen and didn't lose any pressure. Pulled a vacuum on the system and then put recovered refrigerant back in. I replaced the dial thermometer on the walk in and everything is now working normally.