I hope someone can help me with this problem.
The toilet on my main floor which is about 20 years old just started to whistle or whine after the flush is completely finish.
Would anyone know what this means?
If I'm understanding your problem correctly, this is likely resonance-frequency squeal from internal valve when it opens to allow fill-water to enter the tank. Suggest taking the lid off during full-pressure fill and see if you can locate source. Suspect internals calcified to extent that the flow's new path generates this new sound.
Quick test would be to partially close the inlet shut-off on the wall while sound is going on. Usually closing this valve slightly will modulate the sound or make it go away. If it does, that's almost certainly the problem.
If that's it, replacing the guts is messy, but simple and inexpensive.
Thanks for the reply asolo. I will give it a try.
It's become a lewd old toilet... you may want to leave the light off when you go in there.
I agree with the above post... replace the fill valve with a Fluidmaster kit. They are cheap and fast to install. They also are easy to repair when it's time. They also let you know if water is leaking into the bowl.