Before starting the task of removing the rear calipers I would strongly suggest that you soak the bolts with plenty of WD-40 or the like. Loosening the main mounting bolts was probably the hardest part of the process.
The first task is to loosen the wheel nuts before jacking up the rear of the car and supporting it on axle stands. Make sure you have chocked the front wheels before raising the rear. Remove the wheel and this is the view you will see.
As you can see by the amount of rust on the disc surface this was a job that really needed doing!
The picture above shows the things that need to be removed.
1. Removing the brake pads. First remove the two pad springs (a) followed by the pad frame key (b). Once these are removed the pads can be removed. Put the anti noise shims in a safe place as you will need these for the new pads.
2. Removing the hand brake cable. First remove the clip and pin (c) then the parking brake cable E-ring (d). The cable can then be removed from the bracket (e).
3. Removing the flexible brake hose (f). First use a flexible line clamp on the hose to stop the brake fluid leaking when it is removed. Next remove the bolt being careful not to lose the two hose washers. To remove the curved lug (g) that goes into the caliper body gently rotate it slightly one way then the other until it is worked free.
The next step is to remove the caliper pin bolts. The top bolt can clearly be seen in the picture below. Don't remove this bolt fully until the bottom bolt has been removed so that it will hold the caliper until you are ready to remove it. Alternatively just remove the bottom bolt first.
The bottom bolt can be seen in the picture below.
Once these two bolts have been removed the entire caliper can be removed from the vehicle and given an initial inspection. As can be seen in the above photo one of the sleeve boots was missing on mine. This had let dirt get in and it was this that was partly stopping the caliper from operating properly. The other problem with this caliper was that the piston boot had also perished and was in very poor condition.
Once on the bench it is a case of removing any surface dirt and rust. I did this using a steel wire brush on the steel parts of the caliper and a plastic scouring pad on the aluminium parts. Make sure you pay particular attention to the handbrake mechanism parts (see pic below). If they are particularly bad you can remove the bolt and disassemble it to clean it thoroughly.
Carefully remove the sleeve and piston boots. Remove the sliders by pushing them through the caliper body. The piston can be removed by applying compressed air into the bolt hole where the flexible hose was fitted. You can also remove it by turning the piston anti-clockwise.
Check inside the sleeve and piston apertures for signs of wear, cracks, deformation or corrosion. Remove the 2 O-rings from the slider apertures and clean inside using the plastic scouring pad. The centre recess does not contain an O-ring only the outer ones.
Remove the piston seal from the cylinder bore and clean the inside rim.
Next carefully clean the sliders and then check them for signs of damage.
Do the same with the piston, including its inside.
Once everything has been cleaned and checked it's time to put it all back together again. To do this you will need to order two sets of each of the following.
55850-61F00 Pin boot set (£11.42 for the two sets) 55830-50E10 Piston seal set (£36.62 for the two sets)
These come with the necessary lubricating rubber grease that needs to be applied to the sleeves.
If the sleeves or pistons are damaged and need to be exchanged then the following part numbers will be needed.
55431-50E10 Sleeves, disc brake (4 in total) 55840-50E10 Piston/Seal/Boot set (2 in total) (Note that the seal and boot are included in this kit)
First install the O-rings into the two outer recesses in the slider apertures (see close up pic above). Inspect them closely as the edge that comes into contact with the slider isn't actually smooth but has raised sections. Next give the slider a good coat of the rubber grease. Install the sliders into the caliper body checking that they move freely. Next you need to install the boots to either end. The boots are slightly different in design. The pad side boots are flat whereas the caliper side boots have a raised centre.
Next install the piston seal into the cylinder bore, being careful not to twist it. Then fit the piston boot into the groove in the cylinder. The piston is then reinstalled into the cylinder bore by pushing it onto the screw and turning it clockwise. This can sometimes be done by hand or you might have to use a piston rewind tool. Alternatively you could carefully use some very well padded mole grips but be very careful not to cause any damage to the piston.
Once you have done this your caliper is ready to be reinstalled back on the car. Hand tighten the caliper pin bolts up first and check the caliper still slides freely before tightening the bolts fully to 100-130Nm. The flexible hose bolts should be tightened to 20-25 Nm.
When installing the new pads don't forget to use the anti noise shims from the old pads. Coat all metal to metal contact surfaces with copper grease, being careful to keep it well away from the brake pad and disc friction surfaces. This grease serves two purposes. Firstly it will help prevent brake squeal and secondly it helps to prevent sticking if you need to disassemble again in the future.
The next task is to bleed the brakes. You can buy simple one man kits in places like Halfords which make this task a lot easier. Simply attach the tube over the bleed nipple. Loosen the nipple and pump the brake until clear, bubble free, brake fluid runs through.
Before reconnecting the handbrake cable depress the brake pedal a few times so that the braking mechanism can self adjust. If you don't think the cable is adjusted correctly and it's probably best to do this anyway, loosen the bolt on the handbrake lever under the gaiter and tighten it just enough so that all the slack has gone ensuring that the brakes aren't dragging at all. The handbrake should fully engage within 3-8 notches.
Once the above has all been completed you should have a braking system that works perfectly. It's always best to refurbish one caliper at a time so that you can compare the two. If you have a digital camera you may want to take pictures at every stage so that you have a record of where everything goes.
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Refurbish the rear calipers (currently 1920 views)
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