Toilets, Sinks, Showers, Tubs and Disposals - Can't flush toilet...stuck valve

Instead of a conventional flapper the toilet I am trying to repair has a flush valve (Mansfield 210 Universal 11 1/2 In. Flush Valve .... I think) that is a tube that slides up and down the fill tube. The toilet will no longer flush because this flush valve gets stuck on the seal at the bottom of the tank. It feels like tremendous keeps the valve from lifting when the handle is pushed. Could this just be the seal breaking down and adhering to the valve? Or is a suction issue even possible? Short of taking the tank off and replacing the whole valve system with a conventional flapper, etc. is there a way to get this thing working properly again? Thanks for your help.

You need to try replacing the gasket first.When they age sticking often occurs.

Note that there is an old and newer version of this unit.The older unit uses a large thicker gasket with a smaller hole in the center and grooves as well as several other holes.The newer version is just a rubber ring with a much thinner width and larger center opening.

Most good hardware stores and public selling plumbing supplies will carry both types.It is best to take the old one with you for proper matching.

Converting a Mansfield of this type is an involved process of replacing the flush valve.

Great. Answer I was hoping for. I like the 10 minute, $1.25 fix way better than taking the tank off and replacing the flush mechanism. I appreciate the help!

Worked great. Good Lesson too. Too anxious to jump to the "rip it out and replace it all" solutions sometimes when the simplest answer fixes things frequently! Thanks again......although the seal did cost $2.29 instead of $1.25!!