When we do a R&R on a turbo what the customer pays the most for is labor. Why? Cause to do it right you gotta take your time. The turbo is torn down and has an initial inspection. Basically we are looking for what ever caused the turbo to fail in the first place. And there are a lot of reasons, but why we do this (especially for industrial/medium duty) is we dont want to repair a turbo and send it back to the customer after we have found a piece of valve seat in the turbine scroll. Or let them know that oil change intervals should be shortened for the work environment, or a longer shut down procedure should be adhered to. Basically there is a lot that can cause failure, anyway.
After teardown everything is cleaned and measured. Mic the turbine shaft and see where it lies on wear. If it is close to it's nominal size for OE it will need a shaft grind. Just like a crankshaft. Now it requires an OS bearing. In this case it would be a STD/.05. 5 under on the shaft. Next clean the bearing housing thoroughly and determine if there is any damage to the journal area that would require a hone. If its clean measure it with a bore gauge or a poppet gauge and mic. If it is in spec and no taper it's a STD bearing, if not it will need a hone in the journal area requiring an OS bearing, now we have a (.05/.05) bearing.
And we do mark the compressor wheel and shaft location for balancing, but that is only for a reference point. By doing so we shouldn't have take as long to balance by starting where BW started (or Holset, Garrett). But they are balanced everytime. It's just insurance. When all this is done everything is cleaned again and ready for assembly. All internals are replaced and the turbo assembled labeled s/n attached and any notes made. In all depending on what is wrong we take anywhere from 4-8 hrs to rebuild.
There are other steps but this is the basics. We do check thrust (axial play) and side-side (radial play), clearance at the wheel tip and inducer-exducer. It's not hard really just time consuming. And like somebody said earlier, sometimes cheap is good, but we always say we do Cheap, Fast, and Good, you can pick two.:st:
