What are the main things that should be looked at when buying a used turbo?

 

i dont know as much as everyone else - but this is what i do know

1) shaft play, left/right & forward/back
2) condition of the fins, are they chipped

someone else will chime in shortly

 

That's the main things, clearances and wheel damage. There is going to be some side to side play, as long as you cannot get the wheels to touch the housing. There should only be a few thousand's in and out play though. Which pretty much means if you can feel it move, it needs work. Rebuild kits are cheap for the Holset's, not sure about Garrett's or Schwietzer's.

Also there shouldn't be any oil in either the compressor housing or the turbine housing. But...if it is used, and was stored sitting on either end, they will leak oil. The seals are like mini piston rings, and they will leak at rest. You should be able to tell if it was leaking while running or if it's just from sitting around.