Renewing the Rear Brake Pads
Special care must be exercised when changing the rear brakes pad to avoid damaging the brake calliper self-adjusting mechanism.
On cars with ABS brakes it is not advisable to force contaminated fluid back from the caliper pistons, it is recommended that on all cars fluid should be released through the bleed nipple and not forced back to the master cylinder resevoir. On cars fitted with ABS the brake fluid may be under very great pressure at some points in the system.
It is important to use clean uncontaminated brake fluids and friction materials to the correct approved specification. Do not reuse old or contaminated brake fluid. Keep all mineral based oils and greases well away from all rubber parts.
Brake linings may contain asbestos be aware of the health dangers of inhaling dust during repair and cleaning operations.
Support the car properly using proper professional quality trolley jacks and axle stands suitable for the weight of the vehicle. Never work under any part of the vehicle which is not supported by at least two axle stands or an axle stand and a trolley jack.
I have checked this procedure carefully and it is based on many years of experience but the responsibility your and passengers and other road users safety is yours alone not mine so take care and if you are unsure of anything seek professional advice. Andrew W. MacFadyen (4/3/99)
Tools & Materials which may be required:
Procedure:
Chock the front wheels, slacken the rear wheel nuts and jack the car clear of the ground and support the chassis properly using axle stands. Then remove the wheels.
If the wheels are seized to he wheel hub (very common on Rovers) and cannot be release by hammering on the rubber of the tyre with a mallet: Replace the wheel nuts but leave them slack by one or two turns, lower to the ground and drive the car forward and backwards about one or two yards stopping sharply by applying the foot brake.. This procedure should free the wheel from the hub without damage and they can then be removed when the car is jacked off the ground.
Examine the brake disks if they are badly scored or rusted obtain new brake disk(s) before proceeding. Release the hand brake lever fully. After removing the cover on the centre console to gain access, use a suitable socket and extension to slacken back the handbrake adjuster at the handbrake lever. Clamp the flexible hose at the caliper with a hose clamp. Mole grips are used by some mechanics for this, but pad the jaws with a soft material and take very great care not damage the pipe by using excessive crushing force.
Using a wire brush remove any accumulated dirt from the area around the bleed nipple and soak the bleed nipple thread with WD40. Remove the rubber dust cover from the bleed nipple, then using a suitable spanner slacken the bleed nipple one full turn and attach the rubber bleed tube to the bleed nipple. It is impossible to specify a spanner size as a variety of different sized hex may be found on nipples 3/8", 10mm, 11mm or 7/16". Use a ½" AF spanner to remove the caliper retaining set screws. Now slide or pivot the caliper clear of the disc and support using wire from the old coat hanger to avoid straining the flexible brake hose.
Wipe any accumulated debris from the caliper piston and seal. Then wind back the caliper piston clockwise using the Sykes-Pickavant wind back tool. It is essential to ensure that the handbrake cable is not under tension before attempting this or the self-adjusting mechanism in the caliper will be damaged. Do not force the piston back using excessive force. Catch any expelled fluid in a suitable container. Just as the piston returns fully home close the bleed nipple. Ensure that the caliper is properly supported by the wire coat hanger.
Remove the old pads and also the anti-rattle shims. Scrap the caliper guides clean and then lubricate sparingly with Coppaslip. Note a warning light connection is only fitted on the lefthandside caliper. Check the caliper locating guide pins slide easily in and out of the caliper bracket and are not bent or rusted – slide rubber cover back lubricate with Coppaslip if required. While the caliper is off take the opportunity to examine the caliper, cable, flexible hose and pipe work.
Clean the anti-rattle shims -- WD40 is excellent for this – and lubricate very sparingly with Coppaslip. Replace the anti-rattle shims and do a trial assembly of the pads in mounting bracket – they should fit snuggly but be free to slide under light pressure. If this is not the case remove the pads and shims and clean the guides again, remove any rough edges from the metal backing plates of the pads where they contact the guides in the caliper mounting bracket. Refit the caliper and tighten the caliper retaining set screws. Connect the cable for the pad wear warning light. Remove the clamp on the flexible hose and check the master cylinder if topped up with fresh brake fluid. Important: Do not re-tension the handbrake cable at this stage.
Repeat the procedure for the other caliper.
Then pump the brake pedal hard several times to allow the self-adjusting mechanism to compensate for any free play – it may help to start the engine to gain servo assistance. Check the brake pedal is solid with out excessive travel. Check the bleed nipples and pipe connections for any leaks while an assistant applies pressure to the pedal. If air has enter the system it may be necessary to bleed the brakes using fresh fluid.
Now tension the handbrake cable so that the handbrake lever must rise between 8 and 10 notches before fully applying the brake. Apply and release the handbrake a few times, On 800 models at both calipers check the clearance between the stop pin and the handbrake mecahnism. With handbrake fully released-- this should be 0.5 to 2.0 mm (in imperal measurement 20 to 80 "thou" ) and adjust as the cable tension required. Replace the centre console cover.
It is also advisable to check the operation of the both the hand and foot brakes by rotating the wheels hand while the car is still jacked up, the wheels shopuld turn easily without the pads dragging excessively when the hand brake is released. . On Rovers it is especially important to check that the forked end of hand brake cable articulates freely on its clevis pin -- if it is seized to the caliper lever the hand brake efficiency will be severely reduced and the life of the handbrake cable will be shortened.
Apply a little Coppaslip to the inside edge of centre hole on both wheels
to help prevent the wheel seizing to the hub. refit the wheels and tighten
the wheels nuts, remove the stands and then lower the car gently to the
ground. Check the wheels nuts again for tightness
when the car is on the ground. Remove the wheel chocks from
the front wheels.Before using car the test brake
pedal for excessive travel only then and road test exercising caution.
Remember it may take 100 miles or more for new brake pads to bed in and
the brakes to reach full efficiency.