> I have a pair of calipers (those would be "C" in your Moss
> catalog) for my
> TR4. The pistons are rusted into the calipers. So, I took the calipers
> apart (despite dire warnings about torque settings from the
> "Caliper Tip" in
> the Moss catalog) to see if I could ease the pistons out. Have purchased
> new pistons and complete rebuild kit.
>
> Well, I've been soaking these things in Gunk penetrating oil now
> for three
> weeks, and I can't get anything to budge.
Try PB Blaster.
> This afternoon, I had an
> inspiration: drill a hole through opposite sides of the piston,
> then insert
> steel rod through both holes, place caliper in a vise and beat
> hell out of
> the rod to get it to turn and break the piston free. Hurt my hand.
>
> Is there a better way? (Must be.) Any advice is welcome.
One method that works is to reassemble the calipers, and install the bleed
valve. Find a bolt the right thread to go into the inlet hole, drill a
passage through it lengthwise and drill and tap the head to take a grease
zerk. Screw the bolt into place, and use your grease gun to pump the
caliper full of grease. An ordinary grease gun is capable of generating
very high pressures, I've never seen a stuck caliper or slave cylinder this
wouldn't budge. Of course, you'll have a large mess to clean up afterwards
...
Another method is to fill as much as possible of the interior with some
volatile solvent (PB Blaster works well), block off the fittings, and then
apply heat. I use this method mostly on aluminum slave cylinders, where the
differential expansion helps loosen the piston, but it would probably also
work on cast iron calipers. Lots of pressure when the solvent boils.
Of course, with either method, you have the problem of what to do after one
piston pops out. I remove it, clean it up enough to be sure I can get it
out next time, and put it back in. Then clamp it in place with two stout
pieces of steel (Home Depot sells flat 1/4" thick rebar that works well) and
two big "C" clamps. Then repeat the process on the other piston.
Note that with either method (but especially method 2) the pistons come out
with a great deal of force. Don't put your fingers in there ! Eye
protection wouldn't be a bad idea either.
9 fingers Randall
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