I'm afraid to click..... (no offence but really ....Sheldon posting a video about lubricating sticky valves and sliders....
)
But in reality, we've (read beest, professional engineer) tried a few things (hairdryer etc) and have a few more drastic ones on the list, but we thought seeing as there was an expert on board.....
(isn't youtube a marvelous resource, though? beest and hector used it last month to change the clutch on the washing machine and it's like new now!)