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Turbocharge Your MG Midget

Turbo Rebuild

How To
Turbo Plumbing
Turbo Rebuild
Troubleshooting page 2
Neil's (mine) 1098cc
Simon's 1275cc
Paul's 1275cc
Arno's 1275cc
Arno's Gearbox conversion
Charlie's 1380cc

Rebuilding the turbo
Mark the compressor wheel and turbine wheel so they can be lined back up when reassembled. (The turbine wheel and shaft are one single piece)
A 5/8" socket should fit the turbine wheel "nut". If it does not fit, CAREFULLY secure the wheel by this nut in a vice.
Remove compressor nut using 12 point 7/16" socket then remove compressor wheel.
Remove turbine wheel and shaft from center section-- you may have to tap the end of the shaft to get it out. You should now have the turbo broken down into four pieces:
(a) the compress wheel and nut;
(b) the center section;
(c)the heat shield (also called the dog dish); and
(d) the turbine wheel and shaft.
Next, remove the compressor seal plate by removing the 10mm bolts securing it to the bearing housing. Removing the seal plate will expose the following parts:
(a) the compressor seal;
(b) the thrust collar;
(c) the thrust bearing;
(d) the thrust bearing retainer; and
(e) 'O' ring

Remove the two turbine shaft journal bearings from the bearing housing by removing the snap rings on each side. The bearings will/should just now fall out from each side of the housing.
NOTE: there are also two other snap rings located inside of the housing. These do not need to be removed. The stock original bearings are made of Aluminum as this is the material that the GM engineers specified to Garrett. Replacement bearings are not usually Aluminum--they are often made from sintered bronze. There should be numbers stamped into the outer edge of the journal bearings. You will need these numbers when ordering new bearings.

Soak the bearing housing in carb cleaner and check to make sure all oil passages are clear.

Remove the old turbine shaft shaft seal and clean off all carbon around the seal area--this is not easy to do!

Install the new turbine shaft seal using external snap ring pliers to expand the seal--the same way a piston ring is installed. Try to expand the seal only as much as needed to install it. An over expanded ring will make re-installation of the turbine shaft more difficult. As a side note, contrary to what is often believed, this is NOT an oil seal. The purpose of this seal is to keep the exhaust gases from entering the crankcase via the oil return line.

Reassembly Notes

  • Use 105 Lubriplate or Torco Assembly lube to pack the journal bearings and shaft. Plain motor oil can also be used.

    Make sure ALL journal bearing snap rings are installed and seated in their grooves.
  • Make sure all 'O' rings are in place on the seal plate.

    The only tricky part is compressing the turbine seal ring enough so the shaft will slide into the bearing housing. The turbine housing is tapered and the ring and shaft are *supposed* to just slide in IF the seal ring is centered on the shaft and the seal was not over expanded during installation. Hold center section in one hand, compressor side down. Insert shaft into center section until seal touches housing. Rotate turbine wheel with a firm but gentle pressure. This will center the seal in the housing and on the shaft. Then give a slight pressure and the seal will snap into place. It should not be overly forced as other problems may exist if extra force is needed. With normal conditions, this technique should work every time. This may be the most frustrating step of all or you may get it on the first try! This may be the most frustrating step of all or you may get it on the first try!
  • Line up the mark on the compressor wheel with the mark on the turbine wheel. Torque the compressor nut to 18-20 in-lb (that's INCH-pounds NOT foot-pounds) Then continue to rotate the nut an ADDITIONAL 90 to 110 degrees. DO NOT use any sealers on the nut or shaft threads--the nut is self locking.
  • turborebuild4.jpg
    Parts required for the rebuild

    Close up of compressor side undone

    Order of parts left turbine to right compressor nut

    Turbo housing, with broken turbine shaft

    If you want your turbo midget here send me the pics

    Compressor side taken off, note broken shaft

    Compressor side, oil lubrication plate and ring

    Bearing hiding under cir-clip

    No picture to display

    If you want your turbo midget here send me the pics

    If you want your turbo midget here send me the pics

    If you want your turbo midget here send me the pics

    A Big thankyou to Simon for all his help, so I could make my turbo MG

    Link to Simon Athertons web pages