September 3, 2008, 2:14 pm
It says in the Haynes manual you must open the bleed nipple to release brake fluid from the caliper when rewinding rear disk piston (to fit new pads) becasue the master cylinder seals may invert!
Surely brake fluid is always on the move up and down the piping, and what happens if you get a distorted disk.
Is the a case of too much care! (as in don't use toaster in the bath).
If the pistons are returned slowly to thier fully retracted position, is this incident likely to occur.
September 6, 2008, 3:26 pm
should be ok as long as you go slow in rewinding the pistons back this might help
Release handbrake cable from actuator on rear of caliper. The 'good book' says "push the lever forward" to allow nipple on cable end to be lifted from location. I defy anyone to 'push' it. It is attached to a very strong return spring. It must be levered forward, using a large screwdriver between the arm and the lower end of the caliper. Whilst this is done, cable nipple is lifted out, then lever is released. An alternative method is to grasp the end of the cable nipple with a pair of pliers and pull the cable gently backwards and downwards which releases it from the lever without having to push the lever forwards. The end of the cable outer is held by either a spring clip or plastic grommett. Ours had a clip, which is pulled sideways from a groove in the cable outer, thus allowing the cable, which is now free, to be withdrawn clear of caliper.EDIT BY NOHOMERS Just had to do this on my Mk3- You do not have to release the cable, as i tried as per these instructions using locking molegrips, and just couldn't move the lever sufficiently to release the cable. just undo the upper and lower bolts and wind the piston in under pressure!!! just make sure you support the caliper so as not to distort the cable or the pipe.END EDIT Lower guide pin bolt is now removed (1/2 inch AF) and inner caliper frame hinged upwards, leaving pads in position either side of disc. Alternatively, to allow a more thorough "clean up", particularly if the caliper/assembly is rusty, I found it easier to remove both guide bolts (my replacement pads came with new bolts anyway) and remove the caliper completely. This made it easier to get to rusty surfaces with a scraper to ensure the pads moved more smoothly.
Next comes the 'interesting' bit! The piston will be fully extended, as in nornal calipers, and must be pushed back into housing. Unfortunately, because the self adjusting handbrake mechanism operates on a threaded piston located behind the front piston, which rotates as the handbrake is operated and thus takes up any wear, the front piston cannot be returned by normal means. It must be pushed back, whilst rotating it, to screw the threaded rear piston back into the housing. A 12mm hexagon socket is located in the centre of the piston, for this purpose and hence a 12mm Allen key is required! (Haynes, of course, just say use an Allen key). On right hand caliper, the piston must be pushed hard whilst rotating it clockwise. For the left hand caliper it must be rotated counterclockwise. (Estates, it says, are the opposite way round! EDIT BY DOJJ I can confirm that the estate has the passenger side rotating anti clockwise to screw in. I can also conform that the estate uses different calipers to the hatchback and saloon cars and the calipers are NOT interchangeable. There is also a different cable attachement arrangement on the estate compared to the non estate cars END EDIT This task was not easy, and at first I thought the piston was not going to go in. You must persist and push very hard, whilst an assistant holds the caliper. There is a 'caliper winding in tool' available from Halfords for about £12, This pushes and winds the calliper in at the same time. This can save you a shed load of heart-ache.
With piston retracted, general clean up is done with brake cleaner fluid and copper grease applied to all pad contact points. The piston has a long and short cut-out, on opposite sides, and these must then be aligned with a raised casting pip on the outer rim of the piston housing. For reasons I cannot see, the long cut out must be aligned with the pip on the Right hand side wheel caliper and the short one on the Left hand side caliper. The 12mm Allen key is again used to rotate them into their correct positions. The new pads are then fitted, the caliper inner hinged down and secured with the screw, after applying Loctite threadlock.
Reconnect handbrake cable, in a similar manner to when removed.
Apply handbrake several times to take up slack, pump the brake pedal a few times for good measure, check that the disk still moves freely with brakes released (if not you may need to clean a bit more thoroughly). Fit wheel and job is done!
It's quite an involved affair the first time, but second wheel can be done in about 30mins!
September 7, 2008, 1:22 am
I have never used the nipple as i have known a couple to corrode and snap. Never had a problem