Jeff, you have two options to get the piston out. If you have compressed air,
you can hook it up and blow out the piston. Do this with considerable caution
because the pressure can build up significantly and when the piston frees up, it
will shoot out of the cylinder. Place a rag around the caliper opening to catch
the piston and don't get in the way.
The safer alternative is much messier. Fine a grease nipple that fits the
caliper threads and screw it in finger tight ( so as not to distort any of the
threads or damage the seat). Pump the caliper full of grease and the piston will
be forced out. Since the grease isn't compressible, only the trapped air inside
compresses and the piston just pops out with little force.
Go for it!
Vic Whitmore
76 Spitfire
Thornhill, Ontario
Jeff McNeal wrote:
> Hi again. A special thanks to John C. Smith, a list member from Ohio, for
> the many helpful e-mails he's sent me advising me on how to extract my
> caliper pistons for a rebuild. If you want to see how horrible the seals
> looked, I've posted pictures on my project page:
> http://www.ohms.com/spitfire/projects.shtml down near the bottom of the
> page.
>
> My biggest surprise was the discovery that one of the pistons had no circlip
> or outside seal whatsoever. No WONDER this thing couldn't hold fluid in the
> reservoir! Duh! Is it possible that the clip and seal became dislodged and
> lost somehow? Or did someone get sloppy when they last rebuilt the caliper
> seals way back when? I couldn't BELIEVE that when I saw it. As I stood
> there staring at the missing seal, the importance of doing this stuff
> yourself really hit home for me.
>
> Unfortunately, one of the pistons is stuck and I can't seem to get it
> dislodged from the cylinder no matter what I try. I've attempted to wriggle
> it out using needle-nose vise grips (not on the surface that comes in
> contact with the cylinder!), I've tried tapping the outside of the caliper
> with a hammer to break it loose and I've given up for the day after an hour
> of trying. I've sprayed the edges of the piston liberally with WD-40 with
> the intent of trying again tomorrow, after the lubricant has hopefully
> penetrated further into the piston cylinder. Now that I've sprayed WD-40 on
> there, are there any special precautions I should take before refilling the
> system once I DO get that piston out and the new seals in place? In other
> words, will traces of WD-40 cause problems with either the new rubber seals
> or the silicone DOT 5 that I'm going to use? Thanks!!
>
> Jeff
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