Opel Corsa B 1993–2000 Service and Repair Manual: Front brake caliper - removal, overhaul and refitting

Removal

1. Apply the handbrake, then jack up the front of the vehicle and support it on axle stands. Remove the appropriate roadwheel, marking its correct fitted position on the wheel hub.

2. Minimise fluid loss either by removing the master cylinder reservoir cap and then tightening it down onto a piece of polythene to obtain an airtight seal, or by using a brake hose clamp, a G-clamp or a similar tool to clamp the flexible hose.

3. Clean the area around the caliper brake hose union. Slacken and remove the union bolt and recover the sealing washer from either side of the hose union; discard the washers new ones must be used on refitting.

Plug the hose end and caliper hole to minimise fluid loss and prevent the ingress of dirt into the hydraulic system.

4. Remove the brake pads.

5. On models with early ATE type calipers, slacken and remove the two caliper mounting bolts and remove the caliper assembly from the vehicle.

6. On models with GMF type calipers, prise off the mounting bolt caps to gain access to the bolts. Slacken and remove the bolts and remove the caliper from the vehicle (see illustrations).

On the GMF caliper, remove the caliper bolt caps . . .

. . . then unscrew the caliper bolts . . .

. . . and remove the caliper

Overhaul

Early ATE type caliper

7. With the caliper on the bench, wipe away all traces of dust and dirt, but avoid inhaling the dust as it is injurious to health.

8. Separate the caliper body from its bracket by sliding them apart. Recover the guide springs.

9. Using a screwdriver, prise off the retaining ring from the dust excluder then remove the excluder from the caliper.

10. Withdraw the partially ejected piston from the caliper body and remove the dust excluder. The piston can be withdrawn by hand, or if necessary pushed out by applying compressed air to the brake hose union hole.

Only low pressure should be required such as is generated by a foot pump.

11. Once the piston has been removed, pick out the seal from its groove in the cylinder, using a plastic or wooden instrument.

12. Thoroughly clean all components using only methylated spirit, isopropyl alcohol or clean hydraulic fluid as a cleaning medium.

Never use mineral-based solvents such as petrol or paraffin which will attack the hydraulic system's rubber components. Dry the components immediately using compressed air or a clean, lint-free cloth. Use compressed air to blow clear the fluid passages.

13. Check all components and renew any that are worn or damaged. Check particularly the cylinder bore and piston; these should be renewed (note that this means the renewal of the complete body assembly) if they are scratched, worn or corroded in any way.

14. If the assembly is fit for further use, obtain the necessary components from your Vauxhalll dealer. Renew the caliper seals as a matter of course; these should never be re-used.

15. On reassembly, ensure that all components are absolutely clean and dry.

16.Soak the piston and the new seal in clean hydraulic fluid.

17. Smear clean fluid on the cylinder bore surface.

18. Fit the new seal using only the fingers to manipulate it into the cylinder bore groove.

19. Fit the new dust seal to the piston and refit it to the cylinder bore using a twisting motion, and ensure that the piston enters squarely into the bore. Push the piston into the caliper bore making sure that the piston step is positioned as shown (see illustration).

Caliper piston recess setting diagram - early type ATE caliper

20. When the piston has been partially depressed, engage the dust excluder with the rim of the cylinder and fit the retaining clip.

21. Press the piston fully into its cylinder bore.

22. Secure the caliper bracket in a vice and install the guide springs (see illustration).

Fitting caliper bracket guide springs - early type ATE caliper

23. Slide the caliper body into the bracket splines until the body and bracket are flush.

GMF type caliper

24. With the caliper on the bench, wipe away all traces of dust and dirt, but avoid inhaling the dust as it is injurious to health.

25. Prise the sliding sleeve inner dust caps from the caliper housing.

26. Push the caliper sliding sleeves inwards so that the dust caps can be disengaged from the sleeve grooves and removed.

27. Prise off the piston dust excluder.

28. Remove the piston dust excluder from the caliper.

29. Carry out the operations described earlier in paragraphs 10 to 12.

30. Press the sliding sleeves out from the caliper body, noting which way around they are fitted, and recover their sealing rings. Inspect the sleeves and caliper body for signs of wear or damage. Both should be undamaged and a reasonably tight, sliding fit in each other.

31. Check all components and renew any that are worn or damaged. Check particularly the cylinder bore and piston; these should be renewed (note that this means the renewal of the complete body assembly) if they are scratched, worn or corroded in any way.

32. If the assembly is fit for further use, obtain the necessary components from your Vauxhalll dealer. Renew the caliper seals as a matter of course; these should never be re-used.

33. On reassembly, ensure that all components are absolutely clean and dry.

34. Soak the piston and the new seal in clean hydraulic fluid. Smear clean fluid on the cylinder bore surface.

35. Fit the new seal using only the fingers to manipulate it into the cylinder bore groove.

36. Fit the new dust seal to the piston and refit it to the cylinder bore using a twisting motion, and ensure that the piston enters squarely into the bore.

37. When the piston has been partially depressed, engage the dust excluder with the rim of the cylinder then depress the piston fully into its cylinder bore.

38. Fit the new sealing rings to the sliding sleeve recesses and apply the grease supplied in the repair kit to the sleeves. Install the sleeves making sure they are fitted the correct way around.

39. Fit the inner dust caps, making sure they are correctly engaged with the sliding sleeves.

Slide the sleeves into position and press the dust caps into position on the caliper body using a suitable tubular drift.

Later ATE type caliper

40. With the caliper on the bench, wipe away all traces of dust and dirt, but avoid inhalling the dust as it is injurious to health.

41. Press the sliding bolt sleeves out of their bore in the caliper body.

42. Carry out the operations described in paragraphs 10 to 19, positioning the piston as shown in illustration.

43. Ensure that the dust excluder is correctly located in the caliper body then coat the new slide bolt sleeves with washing-up liquid and press them into their bores by hand.

Refitting

44. On GMF and early ATE type calipers, prior to refitting, remove all traces of locking compound from the caliper mounting bolt threads and the hub carrier holes. Apply a drop of fresh locking compound to the bolt threads. Refit the caliper and insert the mounting bolts, tightening them to the specified torque setting.

45. On all calipers, refit the brake pads as described in Section 4 but do not depress the brake pedal yet.

46. Position a new sealing washer on each side of the hose union and connect the brake hose to the caliper. Ensure that the hose is correctly positioned against the caliper body lug then install the union bolt and tighten it to the specified torque setting.

47. Remove the brake hose clamp or polythene, where fitted, and bleed the hydraulic system.

Note that providing the precautions described were taken to minimise brake fluid loss, it should only be necessary to bleed the relevant front brake.

48. Refit the roadwheel, aligning the marks made on removal, then lower the vehicle to the ground and tighten the roadwheel bolts to the specified torque.