walkthrough. I suggest you watch the BMW video at the bottom of this post as well.
Parts & equipment
Discs and pads of course.
Coppergrease.
Axle stand
Brake cleaner or petrol or acetone (to clean parts with)
Tools you will need
5mm allen bit (for brake motor)
T27 Torx bit (for brake disc securing screw)
T55 Torx bit (for caliper, - best to use 1/2" drive)
E12 Torx socket (for caliper)
- Either a LH&RH rear brake piston rewinding tool or
- a normal clamp and a T45 Torx bit You don't need a brake piston rewind tool. if you do this method or
- diagnostic tool to rewind the motor.
Loosen rear wheel bolts 17mm socket (wheel wrench supplied with the car is not strong enough)
Jack up rear wheel, put axle stand under rear axle and lower jack so that most of the weight is on the axle stand... I like to keep the jack in place under the car it makes it easier to re-jack the car up to remove the stand and it is safer.
Remove wheel.
Using T27 bit unscrew the brake disc retaining set screw, can be easier if handbrake is on.
How to release handbrake,
- With key fob, get in driver seat, put car in neutral,
- Release bonnet catch.
- without pressing brake pedal, press start button. To turn ignition on.
- Close or Open windows it does not matter.
- press brake pedal and press parking brake button down To release parking brake.
- without pressing brake pedal, press start button. To turn ignition off.
- Exit vehicle, ignore door alarm, close all doors.
- Wait for dash display to turn off
I think the advice not the remove the plug is probably wrong, as long as the procedure above is followed and then wait for the heads up display to turn off then the car is switched off, you can then open bonnet and disconnect the battery. Now you are certain everything is turned off. So unplugging the brake motor should be no problem. EDIT to add I did the above, and disconnected the battery, and unplugged the driverside parking brake motor plug. When I reassembled and went for a drive I had no problems.
Using 5mm allen bit unscrew 2 small bolts holding brake motor to caliper, pull motor away. and give it a clean with a dry cloth.
Using E12 star socket unscrew 2 caliper bolts
Remove caliper away from brake pads, don't bend the brake hose, don't let it hang on the brake hose, and inspect the brake hose for condition. And make a note of the position of the notches on the piston. They should be perpendicular to the position of the caliper on the car. So when the caliper is held vertically the notches are horizontal.
Now we need to unwind the piston inside the caliper. You can do this 3 different ways.
- by using a LH thread rewind tool for both sides (but check this for yourself, I am only guessing based on what I did manually below (the piston turns anticlockwise)
- by using a T45 bit and clamp.
- by using a Lexia diagnostic box
I used a clamp so I will describe that method. As you press in the piston watch the brake fluid level in the front reservoir, so it does not overflow. If it does rise too much you will need a 10ml syringe (from a chemist) to pull some out. Mine did not move at all.
Use a T45 bit and turn the piston drive clockwise for passenger side and driverside. Turn it clockwise until it stops or begins to turn the piston, then clamp the piston to retract inside. I used a furniture clamp, otherwise called a bar clamp or a quick grip. You don't need a brake piston rewind tool.
Now the piston is retracted..make sure the notches on the piston are in the right position. I moved the caliper behind the suspension strut and it was able to rest there with no strain on the hose. Or you can let it sit astride the top of the brake disc
Now to remove the caliper mounting bracket. Put your 1/2" dr - T55 bit into the caliper bolts, and lying down under the car, pull down on your 1/2" dr bar for passenger side.....and push up on driver side (more difficult), and remove both bolts completely in this way.
Ok caliper removed, remove the old pads, and recover the little clips on the pads, and fit them to your new pads, and note which pad goes on the inside and which on the outside. For the 268mm diameter discs the pads with the bigger horns are on the inside, the smaller horns are on the outside. If you forget, you can look at the old pads and see which ones have the rusty marks with the notches from the piston those will be the pads on the inside. And the inside pads have an upstanding stud to engage the piston notch.
Ok clean the caliper bracket, with a wire brush or a knife and cloth etc. And clean to a polished finish the 4 shiny clips that the pad legs sit in, again with a wire brush.
You MUST fit the the inside pad with the caliper off the car, you do this by putting it inside the caliper and pressing towards the outside of the caliper
Ok now remove the old brake disc, by removing completely the little securing screw with the T27 bit. The disc will be tight as F..k on the hub so just get a hammer and smack it hard from the rear until it comes off. Clean the mating face on the hub as in the BMW video.
Clean the new disc faces both sides with brake cleaner or any decent solvent and a clean cloth. unless your discs are painted in which case just leave them alone. Fit the new disc and secure with the little grub screw and tighten a bit, it's a small screw so don't over do it. maybe 8Nm torque
I put a bit of copperslip/coppergrease or moly grease on the T55 bolt threads to make fitting and removing easier. Note the manufacturer fitted them dry no grease no locking compound, at the end of the day it's up to you whether to grease them or not.
Anyway, refit caliper bracket with inside pad already fitted or with both pads fitted and tighten T55 hard.
refit outer pad. It is easy enough to fit with the caliper on the car as you can see what you are doing, unlike the inner pad.
Tap each pad home flush against the disc with a hammer....I spent quite a while wondering why the piston was not retracting fully to go over the pads, then realised I had not tapped the pads in with a hammer (light taps), then the piston/caliper went straight on no problem.
Fitting the pads, the little clips make this difficult, you have to put the spring of the clip in first, and then press the pad legs against the clip and push the legs into the slot.
Refit the motor to the caliper/piston unit now, because you can see the holes line up and it is 10 times easier to do now and get it right now rather than trying to do it when the caliper is back on the car.
Refit caliper/piston/motor unit now (make sure the brake hose is not twisted) tighten the E12 bolts not very hard - just enough.
Nearly finished now, again wipe clean the brake disc.
Make sure you refit the motor electrical plug if you have removed it.
You can if you want apply the hand brake now, with an assistant, while you watch by the wheel.
Refit the wheel.
Lower the car.
Go for a drive, applying foot brake and hand brake a couple of times.
Below here was my original post...
Hi,
Has anyone here done a self service rear brake discs and pads on a C4 Picasso Mk 2 (2013 onwards)?
I am searching for info but the only info I find is for pre 2013 cars without electric handbrakes.
From what I found so far the pre 2013 have a right hand and a left handed piston rewind in the rear calipers, needing a RH and LH rewind tool
RH tool is £20 - £29
LH tool is £37 - £50 (Laser 3935)
Do you think it is the same on a Mk2 C4 LH & RH tools needed.
I have also seen videos of people using other tools to retract the piston i.e. "angle grinder spanner"
...what happens if you only apply a turning force but no pushing force...i.e. if turned will the piston retract or must it also be pushed at the same time?
I remember I did one before, I think I turned it with water pump pliers, can't remember exactly what I did though. Actually just found this video of a guy just turning while pushing it in himself with the gold cube tool. So no need to buy expensive RH & LH tools? Tell me what you think.
In regard to the electric handbrake, I have seen how to release the parking brake on a C4, but this will only release it not retract it all the way inside.
I found this video, is this what I would need to do?
I found this guy on a BMW using the same technique.
Looks like this is what I will have to do. Anyone know if the mk2 C4 parking motor is removable like this, as some of the videos say some cars do not have the 2 bolts to allow it to be removed.
I wonder if it would be possible to keep applying and releasing the park brake, whilst constantly inserting shims into the gap ....the idea being after the park brake has engaged, it will disengage by a fixed amount, say a full turn, so if every time it disengages you shim it up, so that it cannot engage again to the same distance, and then will disengage by another full turn....and so on and so on,,,, the park brake will eventually wind itself all the way back?
I am also reading that the Torx T55 bolt that holds the caliper bracket to the hub assembly are difficult. Does the mk2 have these T55 bolts as well?