New C4 Rear Brake Pad Clean Or Replacement

[paul.h]

A few notes to help anyone wanting to clean the rear brakes or replace the brake pads.

 

The new C4 from 2010 rear brakes are similar to the previous model which is covered by a Haynes manual. TRW brakes are fitted. The caliper is held to the carrier by bolts and guide pins needing a 13 mm socket and open ended 15 mm spanner 35 Nm. The procedures say the removed bolts should be renewed each time but no reason is given - they were found to have loctite on so possibly that is the reason but they are 10.9 high tensile bolts so unlikely to be stretched and did not look damaged. However, not having new bolts I used the old ones and applied fresh loctite. New bolts are supplied with new pads. The carrier is held on the hub by bolts possibly needing a torx bit 30 Nm plus a further 35°. The wheel bolt torque is 100 Nm for alloy wheels and 90 Nm for steel wheels. The caliper brake hose is a steel braided type with a rubber protective sleeve and may not like being bent/twisted too much.

 

Some cars have an electric handbrake which requires the battery to be disconnected at the start but after fitting all the parts, the battery to be reconnected and then using a diagnostic tool (Lexia) the handbrake has to be calibrated, fault codes read and cleared, the handbrake control activated and then checked it works. Our C4 has a manual handbrake so the following is based on that.

 

- apply the handbrake, put the car in first gear, chock the opposite rear wheel, jack up the relevant corner of the car and support on an axle stand.

- remove the wheel (use the yellow plastic tool to pull off the wheel bolt plastic chrome covers).

- check the brake disc thickness - if worn below its limit then new discs are needed. Our car discs were 9 mm new, minimum 7 mm but other cars may be different.

- check the brake pad friction material thickness - if less than about 4 mm new pads are needed.

- release the handbrake and check the car is still well supported.

- use a screwdriver to move the caliper handbrake lever so the handbrake cable end can be removed from the lever. On the cable next to the cable support bracket is a black plastic ring that needs to be pulled off, then pull the cable out of the support. Put the ring back on the cable so it is not lost.

- unclip the brake pipe from the abs sensor cable and from the next clip along.

- undo the caliper lower guide pin bolt 13 mm socket and use an open ended 15 m spanner to stop the guide pin turning.

- lever up the caliper off the pads and then pull out of the top guide pin hole (or if preferred the top bolt can be removed but this way saves having to replace 2 bolts). Cover the guide pin and hole to keep dirt off/out. Suspend  the caliper from the top of the shock absorber using string/wire/welding rod through the caliper lower bolt hole.

- remove the pads and their sound deadening shims from the caliper. The pads and shims have rubber backings that suffer from use and new shims are supplied with new pads. In my case the pads and shims were ok to re-use after cleaning.

- clean everything up (pads, caliper, carrier, shims, bolts), remove the glaze from the disc using such as 180 grit emery paper, scrape off any loose rust from the disc edge, wipe the disc with brake cleaner, place emery paper on a flat surface and then rub the brake pad friction side on it to remove any glaze.

- if new pads are being used, turn clockwise (applies to both sides of the car) and push the caliper piston in. It may be better to release the excess brake fluid via the bleed screw rather than push it back in to the braking system. Make sure the brake fluid reservoir does not overflow.

- fit the noise reduction shims to the carrier.

- apply a smear of copper grease to the pad/caliper/shims/guide pin contact faces but not on the pad friction material or disc - a bit of card held between the carrier and disc should stop any going on the cleaned disc whilst doing this. The pads have a rubber type backing but a bit of copper grease will also help prevent squeal.

- fit the pads to the carrier and put the caliper back in place, making sure the brake hose has not been twisted - also check its condition, and the guide pin rubber sleeves are not twisted or damaged.

- fit the caliper new bolt(s) 35 Nm or consider using the old ones with fresh loctite.

- clip the brake pipe back to the 2 clips.

- use the brake pedal in short strokes until the pedal goes hard to push the piston out so the pads contact the disc.

- refit the handbrake cable, reversing the removal and check that the caliper lever to stop clearance is 0.1 to 1.0 mm and the handbrake starts to work at one notch, with full on by 5 notches.

- clean up the hub and wheel contact faces and apply a smear of copper grease to prevent corrosion/wheel sticking to the hub.

- check the tyre for nails/etc and then fit the wheel 100 Nm alloy or 90 Nm steel wheels.

- remove the axle stand, lower the car, remove the jack, check the wheel bolts are torqued up and then fit the bolt plastic chrome covers.

- if new pads are installed then these will take a few miles to bed in. Before then the brakes will not be fully effective.