caliper rebuild what did i do wrong?

hello all, rebuilt both front and rear calipers (mk lll) with new seals and ss pistons 6 months and 1500 mi. ago. worked a treat.now front is leaking miserably.rear is still fine.what should i be looking for upon teardown of the front? thanks to all for your help. love this forum.

More info please... Stainless pistons used? Did you clean the corrosion from without scratching the seal grooves?

yes ss pistons, cleaned grooves with tooth brush and brake fluid.dot 3.have not removed the caliper yet waiting on new seals.maybe not cleaned enough?thanks again

It is possible you may have damaged the seal accidentally when fitting the piston.

david levine said:

yes ss pistons, cleaned grooves with tooth brush and brake fluid.dot 3.have not removed the caliper yet waiting on new seals.maybe not cleaned enough?thanks again

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I've always found those grooves need careful cleaning with a scribe (bent end) being VERY CAREFUL to put it in the CORNER where there will be no detrimental scratching on the three flat surfaces of the groove, then scothbrite, 1" brass wirebrush on a Dremel, etc... MIND THE SURFACE FINISH! The corrosion there is hard, like a dental cleaning, :shock: needs scraping to get it free.

If a seal was nicked, as mentioned, likely it would have leaked right away.

I'm not a fan of SST pistons, the dissimilar material creating faster corrosion. Doubtful it's happened this quick though.
(Before the masses begin a flame festival on that last comment, just understand that it's CHEAPER/faster/easier to machine a SST piston than to machine from steel/chrome/grind as original. Sold as an "upgrade", it's really just modern manufacturing methods driving it.)

Keep us informed please... 8)

Ensure they are in the correct way around? Flats go to the outboard or hydraulic pressure side.
BC

Where is it leaking ?
outer cap
bleeder
inlet fitting port
piston/seal

I've seen each separately leak so far except the cap

thanks to all who have replied.have not removed caliper yet. appears to be a seal leak. fluid leaking from behind the pads. will tear down this weekend and will let you know.dont know why i got 6 mos. of flawless service and suddenly develop a leak.

concours said:

david levine said:

yes ss pistons, cleaned grooves with tooth brush and brake fluid.dot 3.have not removed the caliper yet waiting on new seals.maybe not cleaned enough?thanks again

Click to expand...

I'm not a fan of SST pistons, the dissimilar material creating faster corrosion. Doubtful it's happened this quick though.
(Before the masses begin a flame festival on that last comment, just understand that it's CHEAPER/faster/easier to machine a SST piston than to machine from steel/chrome/grind as original. Sold as an "upgrade", it's really just modern manufacturing methods driving it.)
Keep us informed please... 8)

Click to expand...

Chrome can sometimes corrode quicker than stainless steel :!: :shock:

hi all, just an update on my caliper rebuild. well it apears i am an idiot.went to pull the freshly rebuilt caliper and realised the end cap was just finger tight.torqued to 26 ft ibs. bled and it seems to be holding.checked the rear which i rebuilt at the same time and indeed it was tightened correctly. so i either spaced out the front or it loosed itself. i am betting on me being an idiot.thanks again to all who tried to help. but there is no help for being inept.dl

Thanks for closing the loop. Happens once in a while.

I'm not a fan of SST pistons, the dissimilar material creating faster corrosion. Doubtful it's happened this quick though.
(Before the masses begin a flame festival on that last comment, just understand that it's CHEAPER/faster/easier to machine a SST piston than to machine from steel/chrome/grind as original. Sold as an "upgrade", it's really just modern manufacturing methods driving it.)

Click to expand...

Probably correct but mine were in the bike when I bought it early '98 and despite me assembling one the wrong way round once (worked fine) they are still there with one seal change for extra security......18 years and 44,000 miles.

concours said:

Thanks for closing the loop. Happens once in a while.

Click to expand...

A vast majority of us on the forum are hobbyists and shit happens all the time. No need for anyone to beat themselves up about it.

Keith1069 said:

I'm not a fan of SST pistons, the dissimilar material creating faster corrosion. Doubtful it's happened this quick though.
(Before the masses begin a flame festival on that last comment, just understand that it's CHEAPER/faster/easier to machine a SST piston than to machine from steel/chrome/grind as original. Sold as an "upgrade", it's really just modern manufacturing methods driving it.)

Click to expand...

Probably correct but mine were in the bike when I bought it early '98 and despite me assembling one the wrong way round once (worked fine) they are still there with one seal change for extra security......18 years and 44,000 miles.

Click to expand...

That's a good endorsement. :mrgreen: Thanks for chiming in.