Originally Posted by
cyccommute
A seal fail on the plunger also wouldn’t result in the problem Altair 4* describes. Plunger seal failures would result in no resistance at the handle during pumping because the air column being compressed would leak past the seal. The squeal he describes is probably air being forced past the seal as the pressure increases in the tube due to the failed (or failing) check valve but the seal isn’t the problem.
Exactly, IMO.
The increasng pressure/resistance at the pump handle is a sign of 'air with nowhere to go' - so check valve or a problem at the head at the end of the hose, or a Presta valve not loosened, or ???
If it's a simple thing to do, removing the head at the end of the hose, or removing the hose from the pump will help to localize the problem.
Squeaking during pumping by itself and/or decreasing resistance at the pump handle would be (IMO) signs that lubrication of the piston seal was required.