Tanks A Lot
Contributor
The whistle/whine is almost guaranteed to be caused by the spring and piston. I'm leaving the distinct whistle of older flow through pistons without a concave seat aside.
Fiddling with either, e.g. turning the spring end to end or rotating the piston, oftentimes cures the problem. I had stubborn ones, where this did nothing, just like in your scenario. I believe it is due to the combination of spring and piston, with special consideration towards the mass of the two. That may be why slightly polishing the spring ends did the trick.
What has done the trick without fail for me was leaving the system pressurized without any air flowing for a few hours. It's a trick I picked up from an ancient Sherwood manual and even though I was skeptic at first, it worked without a fail so far. I'm waiting for the day when this does fail me...
Fiddling with either, e.g. turning the spring end to end or rotating the piston, oftentimes cures the problem. I had stubborn ones, where this did nothing, just like in your scenario. I believe it is due to the combination of spring and piston, with special consideration towards the mass of the two. That may be why slightly polishing the spring ends did the trick.
What has done the trick without fail for me was leaving the system pressurized without any air flowing for a few hours. It's a trick I picked up from an ancient Sherwood manual and even though I was skeptic at first, it worked without a fail so far. I'm waiting for the day when this does fail me...
