home : Piston Valve Instruments

Corroded Valve Caps and Pistons

An instrument not properly cleaned and oiled will corrode after months of disuse. Valve caps will stick and cannot be unscrewed. Don't use strong-arm methods to loosen them. Don't use pliers or pipe wrench, for you'll mar and break the instrument. Sometimes tapping with a wood mallet or wood hammer will be enough to break the corrosion loose sufficiently that the cap can be unscrewed. Sometimes a little oil left overnight will loosen the cap. If these more gentle methods fail, take the instrument to a good repairman.

To remove a corroded piston is even more difficult. Don't try to poke the piston out of the casing with a stick. The piston is hollow, and the walls are thin. See Fig. 7. This force is liable to stave in the top or bottom of the piston or buckle the sidewall. Put a good penetrating oil in the valve and let it sit overnight. Then try pulling and pushing the piston with a slight rotating motion. If this does not bring success, see your repairman.

Before putting an instrument away for any length of time, apply a little vaseline or tallow to the threads of the valve caps, also a little valve oil on the piston. This will help avoid corroded caps and pistons and will help preserve your instrument. You will have to clean the oil off after storage.