Toilet keeps flushing

Toilets wear out from mineral deposits. Fixn may cost more then new. Googl used commodes first

You should replace your fill valve. They are cheap (around $10), and easy to replace. Visit your local hardware or plumbing shop. Instructions are on most packages. In the meantime, if you have a toilet full of nasty, just pour water right into the bowl, when it reaches a certain level it will flush. If it doesn't flush, you have a clog! Your flapper valve may also be the culprit, if you flush and the water just keeps running into the holding tank, the problem is the flapper! Also cheap and easy to replace. Whenever i have a problem I buy a toilet rebuild kit. They are about $20, and will work with most standard toilets. I hope this was helpful!

The most common reason for a toilet to continue to run is a problem with either the flapper or the entire flush valve itself. The water is slowly draining so the fill valve keeps running.
The flapper is the least expensive and easiest solution, so start their. It's usually around $5. If that doesn't solve the problem, I would purchase a flush valve kit, around $20, and replace your flush valve.
*Note: If you have to replace the flush valve, you have to take your toilet apart. Start with the flapper.

replace the whole valve. It's cheap and easy to do. Probably you can install a universal valve. Look on e-bay or amozon

I’m happy to help further over the phone at https://www.6ya.com/expert/robert_24775b73ca70da93

There is a clog in the line. A plunger usually solves this problem, but you have to use a toilet plunger. Your local hardware store will give you the right tool ($13). If the plunger doesn't work, you need a toilet auger (also called a closet auger), which you can buy for less than $20.

I would ckeck to see where water fill line is inside toilet tank and then adjust flush valve to try to get it to shut off at this point. Not knowing whether your toilet still has original flush valve it is hard to tell you how to fix it. If it has float mounted on rod to flush valve there is usually a set screw on the top of the flush valve in the center. Turn this screw clockwise to make valve shut off sooner. Try to set it so that water shuts off when it is at fill mark. If float is mounted on brass float rod you can support rod closest to flush valve with left hand and carefully bend rod down a little with your right. This will cause flush valve to shut off sooner. If the seat is worn to badly in flush valve you will need to replace it.

Readjust the float. the longer it is the more leverage the fill water will have on it. good luck. The fill valve does come apart and cleaned if there is debri in it. Turn the water off first:)

You have replaced the flush valve completely? If so and the unit is still leaking, you may have a small crack in the tank or your just not getting the tank to bowl fittings tight enough. Also, they make two different thicknesses in the tank to bowl gasket. Make sure you are using the thicker of the two. You posted this under the American Std. thread, so if this is correct, give them a call. There could be a recall on this particular toilet due to a flaw.

The foam block does a few things: It helps with noise level, helps prevent condensation and also takes up space in the tank to lessen water usage with each flush.
Keep an eye on the outside of the tank and if you don't ever notice any moisture on the outside of the tank then I wouldn't worry about it all!!