Volvo Maintenance Hints for 7xx/9xx - Bill Garland's Nuclear ...

2. Remove all hoses from housing; carefully mark position of
compressor housing relative to turbine. You want to mark the
housing to have the correct measurement for reassembly so all the
hoses/connections line up for installation.
3. Remove the compressor housing, and then the exhaust housing.
Try to mark the compressor wheel with the exhaust drive wheel so it
will be assembled in the same manner as it was balanced from the
factory (See Figure 1).
4. Inspect worn areas, such as compressor plate on which the seal ring rides (See Figure 2).
5. Clean all parts. Use a glass bead cabinet if one is available. It
will pay off in the long run, but it must be fine grit! All parts must
be thoroughly rinsed, as residual glass bead will destroy your
rebuild in a very short time (See Figure 3). If glass bead is not
available, a cold carburetor dip is acceptable.
6. Soak all parts until clean. A soft brush may be used to help
remove stubborn deposits. Remember, the cleaner you get the parts, the longer the rebuild
will last!
7. Make sure all oil passages are very clean to allow proper oil flow to bearings.
8. Inspect all parts for signs of abnormal wear. All shaft surfaces should be smooth and pit
free. Bearing bores in the housing should not be scored. Turbine seal area in housing should
be flat — no grooves. Blades should not be bent or broken and should not have contacted the
housing. Do not try to straighten out the blades! They will crack and fail under use.
9. Inspect exhaust turbine seal area for worn-out ring groove (See
Figure 4).
10. The carbon/oil deposits trapped in the main housing could fool
you, as they look like the casting. Poke all around with a sharp
object, and scrape away all the foreign particles! This is a very
important step, as the oil has to drain through the housing without
any restrictions (See Figure 5).
11. Lay out the torn down turbo on a clean area with all the parts ready for assembly (See
Figure 6).
12. Replace brass bushings in housing and lube with engine oil (See Figure 7).