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Mike S.
Mike S., Chevy Mechanic
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Im doing the rear disk brakes on a 91 chevy lumina. The pistons

Resolved Question:

I'm doing the rear disk brakes on a 91 chevy lumina. The pistons will not retract enough(screw in) to get the new pads in. It's not even close. They do turn in, but get to a certain point, and then just spin. Any ideas? Mike
Submitted: 7 years ago.
Category: Chevy
Expert:  Mike S. replied 7 years ago.
Maybe there is some crud inside the bore, you may have to take the piston all the way out and use some emory cloth and clean the bore. Does the other side go in all the way? Try the other side first and see if that screws in all the way. If not maybe it's been so long a time since that piston has been that far in that the bore has developed some crud.
Customer: replied 7 years ago.
I've tried both sides and they both do exactly the same thing.
Expert:  Mike S. replied 7 years ago.

I would take the pistons out and clean the bores.

http://www.autozone.com/autozone/repairinfo/repairguide/repairGuideContent.jsp?chapterTitle=Rear+Disc+Brakes&partName=Brakes&pageId=0900c152800682bf&partId=0900c15280068269#hd1-1-2

OVERHAUL



1988-93 Vehicles

See Figures 5 through 18



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Fig. Fig. 5: Unfasten the nut...



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Fig. Fig. 6: ... then remove the lever



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Fig. Fig. 7: Remove the lever seal and...



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Fig. Fig. 8: ... the anti-friction washer, if used



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Fig. Fig. 9: Rotate the actuator screw...



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Fig. Fig. 10: ... then remove the piston from the bore



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Fig. Fig. 11: Remove the balance spring



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Fig. Fig. 12: Remove the actuator screw by pressing on the thread end



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Fig. Fig. 13: Remove the shaft seal and thrust washer from the screw



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Fig. Fig. 14: Remove the boot, being careful not to scratch the caliper bore



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Fig. Fig. 15: Use ring pliers to compress the retainer...



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Fig. Fig. 16: ... then withdraw the retainer from the bore



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Fig. Fig. 17: Remove the piston locator...



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Fig. Fig. 18: ... then remove the piston seal from the caliper bore

  1. Remove the caliper assembly from the vehicle as previously outlined.
  2. Remove the sleeve and bolt boots. Check the boots and bolts for damage and corrosion.
  3. Remove the brake pad retainer from the end of the piston by rotating the retainer until the inside tabs line up with the notches in the piston.
  4. Remove the locknut, lever, lever seal and anti-friction washer (if installed) from the caliper.
  5. Remove the piston by using a wrench to rotate the actuator screw to work the piston out of the caliper bore.
  6. Remove the balance spring and actuator screw.
  7. Remove the shaft seal, thrust washer and boot.
  8. Remove the retainer using ring pliers and a piston locator.
  9. Remove the piston seal using a non-metallic seal pick.
  10. Carefully remove the bleeder valve. If the valve breaks, the caliper should be replaced.
  11. Inspect all parts for damage and replace if necessary.
  12. Clean all parts in denatured alcohol and dry with compressed air.
  13. Install the bleeder valve.
  14. Install the bracket and bolt.
  15. Lubricate the new piston seals with clean brake fluid and install into the caliper bore. Make sure they are not twisted.
  16. Lubricate the piston locating tool J36627, do NOT install the piston.
  17. Install the thrust washer on the actuator screw with the copper side towards the piston.
  18. Lubricate the shaft seal and install it on the actuator screw.
  19. Install the actuator into the piston assembly.
  20. Install the balance spring and retainer into the piston.
  21. After all the components are lubricated and installed into the piston, install the piston into the bore. Push the piston into the bore so that the locator is past the retainer groove in the caliper bore.
  22. Install the retainer using retainer ring pliers.
  23. Install the boot onto the piston with the inside lip of the boot in the piston groove and the boot fold is towards the end of the piston. Push the piston to the bottom of the bore.
  24. Lubricate and install the lever seal over the end of the actuator screw.
  25. Install the lever and rotate away from the stop slightly. Hold the lever while tightening the locknut to 32 ft. lbs. (44 Nm).
  26. Install the pad retainer in the groove at the end of the piston.
  27. Align the inside retainer tabs with the piston notches. Rotate the retainer so that the tabs enter the piston groove.
  28. Lubricate with silicone grease and install the sleeve and bolt boots.
  29. Install the caliper assembly and tighten the retaining bolts to 92 ft. lbs. (125 Nm).
  30. Bleed the brake system as outlined in this section.

 

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