S3 E-Type

How to get the pistons moving freely.

The Standard Caliper rebuild kit from Girling has the seals, dust covers and bleed nipple covers:

Below you can see the caliper after some exterior cleaning. The dust cover is retained by a groove in the top of the piston and a groove in the bore of the cylinder. Since these are going to be replaced you can tear/cut them apart as needed.

I always find it difficult to get the pistons out using compressed air, so usually lever them out with 2 screwdrivers taking care not to damage the piston groove.

Once out, the pistons are normally partially corroded. These can be replaced, but I opted for the clean-up & re-use option. The calipers need a good clean as 20+ years of sediment & garbage has normally collected inside them. Make sure the grooves are clear of all residues of seal rubber & other garbage.

Getting the new seals in to the bore is easy, but fitting the dustcover a little more involved. Firstly, use brake grease or fluid as a lubricant, fit the dust cover to the bore. Then carefully insert the piston by stretching the top of the dustcover whilst not dislodging it from the bore groove.

Once thats done the piston should push in with moderate pressure. If you have to apply huge pressure something is wrong! Take care not to cut the seals in this circumstance. Once the pistons are half-way in you can fit the top of the dust cover to the seal grrove, as the piston is now retaining the bottom lip of the dustcover so it cant be dislodged. Then the pistons can be pushed fully home:

Remember that after bleeding the brakes you need to pump the pistons out to their proper positions!! otherwise the pedal will go straight to the floor the first few times!! (seems simple but easy to forget!!)