Use this as basis for the tabbed file
Replacement of the tappet boot seal assemblies (ref. MEI kit 5R0400 & 5R0405) can be done with the brake fitted to, or removed from, the vehicle using the MEI brake tool kit (ref. 5K0010 or equivalent).
! The use of impact drivers / air wrenches is not permitted with the service tools.
1. Remove the brake pads. Adjust the tappets forwards using a 10mm ring spanner or socket wrench on the adjuster (do not exceed 25 Nm torque) until the tappet boots are easily accessible. The tappets must not be extended more than 30 mm from the caliper face to ensure the pistons remain synchronised. With a suitable lever (e.g. screwdriver) carefully prise the tappet boot out. Take care not to damage the sealing surface on the caliper cover plate.
Note: as the tappet boot is being replaced it may aid visibility and access to cut the rubber material away.
2. Position the forked wedge tool (M01) between the threaded piston and the tappet boot seal assembly with the stepped side towards the tappet boot. Carefully drive it down with a hammer to release the tappet boot seal assembly from the threaded piston. Keep the tool perpendicular to the piston – do not lever the tappet or damage the piston thread.
3. Remove the tappet bush from the end of the threaded piston. Clean and check the cover plate sealing face and the threaded pistons for damage or corrosion. The pistons and cover plate cannot be replaced and if damaged the caliper should be replaced.
4. Wind back the threaded pistons using a 10mm ring spanner or socket wrench on the adjuster (do not exceed 25 Nm torque). Clean the area of the inner boot and carefully remove the inner boot using a suitable lever (e.g. screwdriver). Take care not to damage the sealing face on the caliper cover plate.
! Opening or dismantling the caliper any further will invalidate the warranty.
5. Wind out the threaded pistons using a 10mm ring spanner or socket wrench (do not exceed 25 Nm torque) to a maximum extension of 30 mm. Check the pistons for damage or corrosion. If there are signs of water ingress beyond the inner boots the caliper must be replaced. Lubricate the piston threads with WHITE grease (ref. 5F1500). Fully wind back the pistons and fit new inner boots over the threaded pistons carefully pushing them into position in the cover plate.
6. Ensure that the old tappet bush is removed. Position tool combination M02 & M03 over the boss of the threaded piston and wind out until M03 touches the brake disc. If the caliper is removed from the vehicle add tool M04 (between M02 & M03) and wind out until M03 touches the outboard pad abutment face of the caliper.
7. Press the inner boot over the threaded piston. Use a 27mm A/F spanner to turn M03 against the brake disc until it stops whilst stabilising M02 using a second spanner. Remove the tool and repeat for the second piston. Check for correct fitment of the inner boots: wind out the threaded pistons approx. 10mm by turning the adjuster with a 10 mm ring spanner. Check that the inner boots do not rotate with the threaded pistons. If the inner boot rotates, then the boot must be removed and the procedure repeated using a new inner boot.
8. Clean and check the cover plate sealing face and the threaded pistons for damage or corrosion – these cannot be replaced and if damaged the caliper must be replaced. Lubricate the inner abutment face of both tappet heads with BLACK grease (ref. 5F1505) being careful not to transfer the grease to other components.
! Only use the correct grease provided in the MEI repair kit.
9. Fully wind back the threaded pistons using a 10mm ring spanner on the adjuster until they stop – do not exceed 25 Nm torque – and then wind forward one full turn. Fit a new tappet bush onto the boss of both of the threaded pistons. Fit the new tappet boot seal assemblies over the tappet bushes on the threaded pistons, pushing them into position. To complete the fitment of the tappet boot seal assemblies, use tool combination M03, M05 & M06 for fitment on the vehicle, adding tool M04 (between M03 & M05) if the brake is removed from the vehicle.
! Tool M07 in MEI tool kit 5K0010 is not required for MEI calipers.
10. Position tool combination M03, M05 & M06 so that the closed side of M06 touches the brake disc. Wind out M03 using a spanner to press the tappet boot seal assembly until it stops.
11. If the caliper is removed from the vehicle then add tool M04 (between M03 & M05) so that the closed side of M06 touches the outboard pad abutment face and wind out M03 using a spanner to press the tappet boot seal assembly until it stops.
12. Release the tool and turn tool M06 over, within M05, so that the open side of M06 makes contact with the tappet boot seal. Ensure it is centralised on the tappet.
13. If the caliper is removed from the vehicle then add tool M04 (between M03 & M05). Press the tappet boot seal into place by winding out M03 against the brake disc, or the outboard pad abutment face if the caliper is removed from the vehicle, until it stops. Repeat the process for both tappets.
14. After assembly check that the tappet boot seal assemblies are securely attached by pulling them lightly by hand. Check that the tappets are free to rotate slightly in each direction, taking care not to over-stress the tappet boots.
Note: LV225 & LA225 tappets (ref. MEI kit 5R0405) are identified by an annular groove on the outer face.
15. If the caliper has been removed from the vehicle then replace as detailed in the GUIDE SLEEVE SEAL AND BUSH REPLACEMENT section. Refit the brake pads as described in the PAD REPLACEMENT section (this can be found on p.7-8 of the MEI Caliper Maintenance Guide).
Note: If the brake is removed from the vehicle then new axle mounting bolts should be used for re-installation.