Rebuilt Caliper Now LEAKING!

[Fishcop]

I've just finished rebuilding my front and rear calipers and adding new flexible brake lines (all parts from Pelican )

My problem now is as I have begun to replace the fluid, there is a leak from the rear left M caliper at the piston. All pistons were carefully cleaned using alcohol and a light buff with scotch-brite and the seal kits were genuine ATE. I also assembled the calipers with a light coating of silicone (brake approved) grease. I did have trouble pushing virtually all the pistons back in to each caliper, but ounce I used two clamps on either side of the piston to adjust lateral pressure, there was no problem. I should note also that there was no pitting or surface problem on any of the pistons.

What could be happening here? I didn't think there could be too much problem with "pinching" the internal seal, but maybe I'm wrong? Any and all ideas greatly accepted!

Thanks

[TimT]

the seals are kinda square-ish, check the seal that is leaking. hope that the piston didnt grab it and rotate it in is groove.

unfortunately this means removing that piston.. check the seal and look for tears..

[Fishcop]

Thanks Tim, I reckon you're telling me what I think I know deep down inside

I hate having to re-do things!!!

Do you think I'll need a new seal?

[TimT]

if the seal didnt tear it should be just fine. replace it and really try to ease the piston home

to check kinda stretch the seal between your fingers and feel if the are any tears. If you feel a nick or tear check it out...... if its to bad hope you didnt toss the old seals

Im,sharing because BTDT

[island911]

FWIW, I put an S-caliper back together with the old original seals, and pited pistons. It was just an experiment, for me, to get an idea of the tolerance of the seal to pits. (I wanted to see how much it would leak) It is still on the car and dry as a bone.
So kind of like sparkplugs, maybe they're happier w/o the goo.
Also, the first thing I did after bleeding the cal, was to jam on the brake pedal. Maybe this helped (?) . . . you did say "Any and all ideas "

[Fishcop]

Hope I kept the old seals? Guess when the bin went out ... this morning!

Oh well, thanks guys I guess my weekend won't be as quiet as I thought!

[cab83_750]

Since you welcome all ideas (or Q's), would the position of the piston make a difference. I rebuilt mine (successfully), and I followed the 'angle' requirements.

BTW, without using 1500 sandpaper, it would have taken me hours to remove the crud built-up!

[Fishcop]

Thanks for the ideas everyone. I pulled the caliper and removed the pistons. I had completely sheared both seals forcing the pistons home! I was lucky enough to get to a brake supply place and get two more seals (not genuine...It'll be interesting to make a direct comparison) before the weekend. It was suggested that I lubricate the seals well and then stretch them between my finger to enlarge them before inserting them into their groove, apparently they will slowly contract around the newly inserted piston. Sure enough the pistons slid directly in and no leaks.

Cheers

[Joeaksa]

John,

Put the seals in some brake fluid (I use a saucer) and let them sit for a while before you put them in the caliper. Then slowly push the pistons in after you have lubed them as well...

Should work if everything is lubed up well...

Joe