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Home >> GMC >> 2018 >> Acadia Denali, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 251 (Disc Brake System) >> Repair Instructions >> Front Brake Caliper Overhaul (J55) >> Disassembly Procedure

Disassembly Procedure

WARNING: This page is about a different car, the 2017 Cadillac ATS. However, it is still accessible from the selected car via links, so may be relevant.
WARNING:

Do not place fingers in front of the caliper piston(s) in an attempt to catch or protect it when applying compressed air. The piston(s) can fly out with force and could result in serious bodily injury.

CAUTION:

Use clean cloths to pad interior of caliper housing during piston removal. Use just enough air to ease the pistons out of the bores. If the pistons are blown out, even with the padding provided, it may be damaged.

NOTE:

It will be necessary to fabricate one or more blocks of wood to the following dimensions to be used during this procedure:

  • Must fabricate 1 block: 19 mm (3/4 in) X 51 mm (2 in) X 51 mm (2 in)
  • Optional to fabricate 1 block, rather than using an old brake pad: 19 mm (3/4 in) X 51 mm (2 in) X 127 mm (5 in)
  • Optional to fabricate 1 block to cushion piston removal: 19 mm (3/4 in) X 51 mm (2 in) X 127 mm (5 in)
    Fig 1: Exploded View Of Caliper
    GM1381159Courtesy of GENERAL MOTORS COMPANY
  1. Remove the brake caliper from the vehicle. Refer to Front Brake Caliper Replacement (J55) .
  2. Drain the brake fluid from the brake caliper.
  3. Place the caliper in a vise using plastic vise caps or suitable material to protect the caliper mounting bosses from the vise jaws.
  4. Remove the brake caliper bleeder caps (1) and valves (2).
  5. Using care to not scratch or mar the painted surfaces or piston bore, remove all the brake caliper piston dust boot seals (3) using a flat-bladed tool. Discard the dust boot seals.
  6. Place an old brake pad or the fabricated 127 mm (5 in) long block of wood over 2 adjoining piston bores and secure in place with a non-marring C-clamp.
  7. Place the fabricated 51 mm (2 in) long block of wood over one of the opposing piston bores and secure it in place with a non-marring C-clamp.
  8. Use clean cloths or the other fabricated 127 mm (5 in) long block of wood to pad the interior of caliper housing during removal of the piston.
  9. Carefully remove the brake caliper piston (4) by directing low pressure compressed air into the brake caliper inlet hole.
  10. Move the fabricated 51 mm (2 in) long block of wood over the emptied piston bore and secure it in place with a non-marring C-clamp.
  11. Move the clean cloths or the other fabricated 127 mm (5 in) long block of wood to pad the interior of caliper housing during the removal of the piston.
  12. Carefully remove the brake caliper piston by directing low pressure compressed air into the brake caliper inlet hole.
  13. Repeat steps 6 through 12 for the opposite side of the caliper.
  14. Using wooden or plastic tool, remove the brake caliper piston seals (5) from the piston bores. Discard the piston seals.
  15. Remove the caliper from the vise and clean the entire caliper with denatured alcohol, or equivalent.
  16. Dry the caliper piston bores with non-lubricated filtered air. Make sure the external crossover pipe and the internal fluid ports are clean and free of obstructions.
  17. Inspect the caliper cylinder bores and piston seal counter-bores for scratches, cracks, pitting, and/or corrosion.
    18. NOTE:

    Do NOT clean the caliper piston bores by honing or cleaning with abrasives.

  18. If the caliper piston bores are scratched, cracked, or pitted, or if corrosion cannot be cleaned with denatured alcohol, replace the caliper assembly.
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