The squeak could possibly be air passing by the check valve, like the reed on a wind instrument.
I rebuilt one of mine with a Mac1 O ring piston. If I pump it briskly it will squeak right at the end of each pump stroke. Pumped a little slower it does not squeak. The tendency to squeak gets worse as the pressure goes up. I’m thinking my problem is the O ring seal “burping” air past the seal when it is pumped too hard. I’ve never heard a parachute seal squeak on any of my Crosman’s unless it needs oiling.
Quote from: Blowpipe Sam on May 18, 2022, 10:07:02 PMI rebuilt one of mine with a Mac1 O ring piston. If I pump it briskly it will squeak right at the end of each pump stroke. Pumped a little slower it does not squeak. The tendency to squeak gets worse as the pressure goes up. I’m thinking my problem is the O ring seal “burping” air past the seal when it is pumped too hard. I’ve never heard a parachute seal squeak on any of my Crosman’s unless it needs oiling.Sounds like you may have a belled out pump tube
Quote from: OTmachine on May 18, 2022, 10:47:36 PMQuote from: Blowpipe Sam on May 18, 2022, 10:07:02 PMI rebuilt one of mine with a Mac1 O ring piston. If I pump it briskly it will squeak right at the end of each pump stroke. Pumped a little slower it does not squeak. The tendency to squeak gets worse as the pressure goes up. I’m thinking my problem is the O ring seal “burping” air past the seal when it is pumped too hard. I’ve never heard a parachute seal squeak on any of my Crosman’s unless it needs oiling.Sounds like you may have a belled out pump tube Thanks for the tip. I’ll check it with some calipers. Fortunately I have another 1400 pump tube if needed.
My Benjamin 132 squeaks and my assumption was the inner chamber was wore from use. I am pretty sure the squeaking is from air escaping past the plunger. I made an o'ring plunger and that helped but it still is underpowered. I will have to check the OD for bellying. Thanks for the tip.
I haven't tried a backup ring but I have plenty of area on the piston to try it. I think an o'ring should work. I do have some teflon seals from McMaster Carr that may fit. Think I will try double o'rings first and see what velocity I get. Thanks again.Jim