I have a 12-year old refer sys; its a single compressor unit that feeds a 1/4" "T", with each leg going through a solonoid valve and then to a cold plate in the refer or freezer box. I have significant corrosion on most all parts of the compressor, but no apparent leaks. My compressor starts and runs OK, but the sight glass goes from nearly full to approx 1/4 full, the hermetically-sealed compressor gets so hot you can't touch it, and the boxes both cool to about 40 degrees F; the compressor runs until it overheats and shuts off (12-18 hours later). The cooling water flow remains constant, and warm (not hot). I've had the system checked for leaks (none found) and the DX valves adjusted--all without change in the performance. I don't know where to look next-any suggestions/help would be most apprteciated.