Hello,

When you get the pistons out, check for pits in the pistons and clean throughly. Clean all the oring grooves carefully and check for remanants of the seal and for dirt.

To assemble, first lube the bore and the square orings with clean brake fluid and install orings in each bore of the caliper. Use ONLY DOT 4 non-synthetic brake fluid and I prefer Castrol brake fluid.

Then you have to install the dust boots in the outer groove.

Next, lube each piston with a little clean brake fluid.

Installing the pistons is the tricky part as you have to install each piston through the dust boot while makeing sure that the dust boots stays in their groove. I use a small piece of wood to push each piston in after I have hand started each piston into the seal. Before you are push each piston the rest of the way in, double check to be sure that the dust seal is properly positioned in its groove.

I will check and see if I have a broken caliper seal kit to replace your missing large piston oring and I think I do.

--
Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90501