The R-4 can rattle on for a very long time, if you can live with it. I put an $89 reman R-4 on my 123 diesel in about 1994. (Hey, it was pre-Mercedesshop and I didn't know any better...) It was starting to rattle when I sold the car in 1999, but didn't die until 2001. I would have replaced it because the noise was so bad, but I sold it to a cheapskate friend who never repairs something until it's *really* broken.

The general concensus around here is to only purchase a brand new R-4. They're relatively cheap as compressors go. I seem to recall some discussion of cheap, Asian manufactured knockoff copies of the R-4 that don't last too well even from new. Be sure to get the real thing.

- JimY