I replaced a Trane 2-1/2 to heat pump outdooors 7 years ago, I did the a/h 5-years ago, I get a call no cooling, find no refrigerant in system, pressuru=ize dry nitro hear a big one, take off top cover discharcharge line wires were tied to 3/8" copper line (lucky copper) believe it or not 24volts it blew a hole /melted big enough to sick a pencil eraser in, I cut it out put in cuopling, leak check again at 60 psi I think I hear something crank it up to 350psi, hear sometning at top where cover/spine fine is, I spray alot of leak dect. around area the thing had 3-leaks in spine. So I get new XR-11 2-1/2 ton to replace yesterday, cut suction line, (ive seen it before over the years but never as thick) black/green goop thick as hell, stink like you wouldt believe, put small finger in suct. and keep pulling out this stuff, and like small pieces of hard tar. Outdoor fan was running when I 1st. went. So I was going to put on driers till I saw it was so bad, unit is ground, pipes go thru brick wall, into shettrocked closet, Iam going to cut wall, run new tubing replace indoor coil, new screen, what a can of worms, the thing is If I put driers on it might clean it up if I replace let run 24hrs, replace again. Lineset is very, very short 6-8 feet. Iam lucky theres 35 units On roof if it happened to one of those I would just use driers. If you stick you finger in suction, or twist up a rag and push it in there it will clean up to bright copper. And believe the 24volt discharge line put the big hole in 3/8" line there was even 4-5 small pcs. of what looked like when your soldering and tiny pc. falls to ground, BUT GUYS WHAT IS THIS SLUDGE! Compressor oil winding/insulation mix! STINK!