I let water sit in my pressure gauge a little too late last fall, resulting in a pegged gauge. The inner tube deformed, so I tried to replace it...A little googling and these gauges (teleflex sahara) are not made anymore and are over 60$ to replace, so I figured I would take a shot at fixing it. Nothing to lose anyways.
I carefully opened the plastic case with a hacksaw. Fortunately my tube was intact and not leaking, so it had just deformed due to the expanding water. I carefully bent it back by hand such that the needle just rested on zero (pic 3) with no pressure. Any deflection in the tube causes the needle to move freely and returns to zero with no pressure. I tested it with my air compressor and it worked really well, was within 3 psi all the way from 0 to 30 psi on my regulator. Then epoxied the case back together, it is ready for re-installation.