Nissan Repair: Ac compressor rattle, nissan bluebird sss, replacement compressor

Question
The AC compressor on my Nissan Bluebird SSS SR18 U12 1989 right-hand drive (I live in the Caribbean) automatic started rattling and not cooling a couple months ago. Upon inspection black sludge was discovered inside the entire system.  I changed the AC compressor, evaporator, dryer and condenser and cleaned all the lines, vacuumed the system, new oil and refridgerant (134A). The AC worked beautifully for one day then the annoying rattle returned on the AC compressor and frankly I am baffled. When the car is idle there is just a low rattle, as I accelerate the rattle gets louder, faster and more pronounced.  The fans are good as they cut in noiselessly and normally when the AC is off. (The replacement parts were from a wrecking yard).  the puzzling thing about the rattling is that it is exactly the same noise and behavior as when all the original parts were there.  Your opinion is appreciated.

Answer
Colin,

A couple of things make the compressor rattle.  First, the system can be low on compressor oil.  Remember that the R134 system uses PAG oil and not mineral oil.  If the system was from a 1989 it was an R-12 system.  If the tolerances on the used compressor were out as in it is worn too, and the use of the R-134, in combination, could be the culprit as it relates to the knock.  The old R-12 provides more lubricity for the system since it uses mineral oil and not the polyester oil.  Also, if the system was not perfectly clean some debris has made its way back around the system into the replacement compressor.  Do not ask me how I know about this one since I have had several systems do the same thing you describe, with used parts.