Regarding Dave Talcott's leaky bellows pump, I thought I might offer
a couple of suggestions:

I tend to shellac (or re-apply shellac) to the insides of these bellows
now, since in most cases they have become very porous over time.  If the
wood sucks up many coats of shellac you know you've found the source of
the leak.

Another problem I encountered on a standard Aeolian set of feeders
(pedals) was the slight separation of the laminate between the inside
and outside of the boards, starting to come apart in the middle of the
holes drilled for the flap leather.  (These holes should also be well
sealed with shellac)

If the separation is minimal, a mixture of regular wood glue -- diluted
25% or less with water using a syringe or hypo-oiler (page 45 Schaff
piano supply) -- injected into the separation and well clamped will
usually hold air and solve the problem.  This makes a big mess as the
clamps squeeze out the excess glue, but it will save you from having to
carve one out of new wood.

Lastly, I made a terrible mistake some time ago by ironing the bellows
cloth on, but I had the iron temperature set way too high.  The result
was the shrinkage of the rubber sandwiched between the heavy canvas.
Of course it _looked_ fine, but upon ripping them open to find the
source of the leak I realized what I had mistakenly done.  With the
price of bellows cloth being sky high I can't afford to make that
mistake again!

Hope this helps,
Eric J. Shoemaker
Tacoma, WA