My parents' 2014 Chevrolet Spin Diesel compressor shaft seal was leaking. We replaced the seal and shaft's ball bearing (located between the seal and clutch plate), add about 44mL PAG oil into the compressor (before compressor disassembly there is almost no oil in it), reinstall the compressor, vacuum, and then fill AC system with refrigerant. Leaking problem gone, AC seems worked properly for a few hours of operation, and then compressor clutch always failed to engage. At that time, air gap between clutch plate and pulley was about 1.2mm. Then we remove the clutch plate and found that the bearing had moved slightly outward. We tapped the bearing lightly so that it sat back to original position and reinstall the clutch plate. The gap was about 0.4mm. AC seems worked properly again now, however the gap gets wider after few hours of operation (now about 0.8mm). I'm afraid that the same problem will soon happen.

My question is:

  1. by design, what keeps the bearing in its position? I don't see any snap ring or similar that preventing the bearing from moving outward.
  2. what is possible causes of the bearing moving outward by itself?
  3. what can I do to fix this problem, other than obvious compressor replacement?

The compressor is scroll type, label says "GM" "QS90". Except electrical connector and pulley, the compressor is visually very similar with QS90 (possibly made by Mitsubishi Heavy Industries) installed in Mitsubishi ASX. Below is screenshot from Mitsubishi service manual, showing where the bearing located. The bearing location is exactly the same with my compressor.

enter image description here

EDIT: finally clutch engaging failed again-possibly when revving engine to redline. About ~14ml of greenish clear oil drained from the compressor. some more photos:enter image description here

enter image description here

enter image description here

  • Are you sure an inner or outer snap ring isn't used? An outer snap ring would fit onto a groove on the shaft. Inner snap ring would fit into a groove in the casing. Examine the front end again carefully for a case or shaft groove. Worse case scenario might be cleaning off the shaft and outer race surfaces clean of oil and use red loctite for a permanent adhesive, bonding innder and outer bearing surfaces to shaft and compressor case bore to hold the bearing in place. All surfaces must be clean and free of oil for red loctite to work. Ac pressures and can force the bearing to travel.
    – F Dryer
    Commented Aug 23, 2023 at 9:42
  • You said the bearing is moving outward. This seems counter-intuitive to me. The AC pulley is what is using the bearing to spin free. If the bearing was moving outward, the pulley should be moving with it, which would make the gap tighter, not larger. Regardless of that, what holds the bearing in place is friction on the shaft. Agree with @FDryer assessment of using a spot of red Locktite on the shaft to keep it in place. Commented Aug 23, 2023 at 11:01
  • @FDryer Dryer Compressor case has groove preventing the bearing going further inside, but I didn't see any snap ring keeping the bearing from going outward, which puzzled me. Currently the compressor is installed in the car. If the clutch failed to engage again, I will disassemble it and add some photos if possible. Thanks for the idea of using adhesive, it will probably be my last resort.
    – bas
    Commented Aug 23, 2023 at 11:23
  • @Pᴀᴜʟsᴛᴇʀ2 in my compressor, pulley and shaft has its own bearing. Pulley bearing (inner portion of #7 in the attached picture) is sandwiched between snap ring #6 and bulge on compressor body (sorry for my bad english, probably bulge is incorrect word). The pulley bearing does not move-no problem with it. The clutch plate #4, nut #3, shim #5, shaft bearing (which marked with blue line in the picture), and shaft, seems gradually moving outward together, making clutch plate #4 farther from pulley #7, until clutch failed to engage.
    – bas
    Commented Aug 23, 2023 at 11:40
  • My new understanding is your shaft (along with its internal bearing) is pulling out of the compressor? (And, your English is just fine! It's my pea brain which is at issue, lol.) If so, then having some Locktite between the outside bearing race and the case would work very well. Commented Aug 23, 2023 at 12:58

1 Answer 1


Where's the bearing related to this compressor?enter image description here

  • the bearing in question is inside bore. See my 2nd picture: the bearing is installed in place, it has a black cap. "Is this a machined groove for a circlip?" yes, it's circlip for pulley bearing, not the bearing in question.
    – bas
    Commented Aug 28, 2023 at 22:36
  • Is the black cap a bearing seal or compressor seal against high pressure refrigerant trying to get past seals? The roller bearing seems to be fixed against movement and I can't tell from those snapshots. If this compressor is the one in your car, was the end seal replaced? It's difficult examining compressors and configurations unless seeing them in person. I am by no means an expert but did replace a leaking shaft seal decades ago for an r12 system. Disassembling a vane type compressor for a forum to show images was beneficial for me to learn how variable displacement compressors operate.
    – F Dryer
    Commented Aug 28, 2023 at 23:38
  • The black cap is bearing seal. The roller bearing is fixed, however, the roller bearing does not prevent compressor shaft's axial movement. Yes, it's my car's compressor, and yes, the end seal was replaced. I'm understand that it's difficult to examine compressor without seeing directly, even sometimes we need to grab turn wiggle some parts of it to get a better understanding.
    – bas
    Commented Aug 29, 2023 at 5:01
  • When disassembling this compressor, no small feat, was there any spacer on the compressor shaft to prevent longitudinal travel? Something may be missing and causing this unusual problem.
    – F Dryer
    Commented Aug 29, 2023 at 11:02
  • as long as I know, no spacer on the shaft, but of course I could be wrong
    – bas
    Commented Aug 30, 2023 at 6:47

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