I have been having some issues with my silca pista pump. It has been leaking air out of the top of the pump. I have checked the leather inside (it looks brand new pump is less that 2 years old), but regreased it anyway. Any Ideas what might be wrong?

Blowby at the piston (leather cup) can be from a number of causes, including a nicked or rolled edge, a sloppy or loose fit on the rod, or an over oiled soft piston which is so soft it distorts at high pressure.

The design is such that pressure presses the piston against the cylinder, but if the extreme edge isn't perfect it won't hold an effective seal. Picture a car windshield wiper, when new with sharp corners, you get dry streak free glass. But as it wears, or gets nicks it lets water sneak by under the edge leaving streaks and smears.

Sometimes, you can save the piston, by shaping it in your hand and carefully fitting back into the pump, but more often a piston that allows blowby is DOA and needs replacement.

Thanks I will check the edge of the piston. I am kind of dissappoined in silca, there were all sorts of metal shavings in the pump that were a PITA to clean out, and which i bet marred the piston...

I'm sorry to hear that. The Silca floor pump has been the gold standard for decades in PV floor pumps for half a century. Most people only buy one in their lifetimes, and use them for decades with zero maintenance.

Yep it is a quality tool, Just some stray metal shavings that make it significantly less effective than it should be. A little bit of work and I think it will be great.

BTW- replacement pistons are available, and don't have to be Silca specific. All that matters is that they're for the same ID cylinder. OMAS, and SKS both made (still make?) pumps that use the same piston, so finding a new one at low cost shouldn't be an issue.

I love my Silcas but some do work better than others. I don't think I ever heard of shavings in a Silca but it is possible. Is the nut tight? Aside from a dry leather washer the nut being loose can cause it to let air past. Did you check the valve in the bottom? It might be fouled and need a little oil.

Both of my Silcas are older and never needed anything but an occasional new rubber gasket in the Presta-only bell head. It's disappointing to hear of your problems. I expect the shavings nicked the edges of the washer and lead to the leakage issue. A dirty or sticky check valve leads to air blowing back from the tube or hose and pushing the plunger back up, not leaking out the top.

Mine had the barrel come unscrewed from the base, maybe to purge the shavings left
from a Friday night QC. lapse.