Replaced toilet fill valve - now bowl water level a bit lower

hi Patricia.
Overview Toilets haven't changed much in the last 80 years. After a flush, water still fills a tank, lifting a float that shuts off the water when it reaches a certain level. A lever still opens a flapper to cause the flush, falling back into place when the water level drops. So it's no surprise (nor any consolation) that we face the same flush problems today that our grandparents did. Sometimes the flush is too wimpy, sometimes the toilet keeps running, and sometimes the bowl doesn't refill.
Our ace plumbing consultant has a simple four-step strategy to solve 95 percent of these problems. You can complete the first three steps in five minutes. That'll solve most problems. The fourth step is usually easy too, but not always. More on this later. These steps work for most toilets but not for pressure-assist models.
Check the fill tube

Overflow tube problem

Push the fill tube firmly onto the fill valve. Make sure the fill tube sends water into the overflow tube.Remove the tank lid and find the fill tube. It's a small flexible tube that runs from the fill valve to the overflow tube. While the tank refills, this tube squirts enough water down the overflow tube to refill the bowl after the completed flush. If this tube falls off or the water stream misses the overflow tube, the bowl won't fill and your next flush will be wimpy (that is, won't develop a strong siphon). Reattach the fill tube and make sure it perches about 1 in. above the rim of the overflow tube. Flush the toilet and watch the water stream to make sure it goes down the overflow tube.
Adjust the fill height

Check the float

Adjust the float to set the water level. Pinch the clip and slide the float up or down on the rod. Keep adjusting the float until the water shuts off at the proper level.The water level in the tank is controlled by an adjustable float. A float that's set too low produces a weak flush; if it's set too high, water spills into the overflow tube and the fill valve won't shut off. The toilet keeps running. Look for the fill level mark on the inside back of the tank and mark it on the overflow tube so you can see it more easily. If you can't find it, measure down about 1 in. on the overflow tube and make a mark. Then flush the toilet and see if the water reaches and stops at that mark. If not and the toilet keeps running, adjust the float up or down. If you have an old toilet, you'll have to bend the brass rod that connects to the float ball to make adjustments. But with newer toilets you usually turn a screw or slide a clip along a rod. Flush the toilet after each adjustment.
Also make sure that the water level is at least an inch below the C-L (critical level) marked on the fill valve. You can adjust the height of many valves to raise or lower the C-L.
Occasionally the fill valve simply won't shut off, which means that it's defective. If so, turn the water supply off at the shutoff under the tank. Buy a replacement valve (sold at hardware stores and home centers). You don't have to match the old one; many, like the one shown, fit most toilets. It's a 15-minute change-out.
Adjust the flush handle/flapper chain

Flapper chain fix

Adjust the chain to leave a little slack with the flapper closed. Then cut off the excess, leaving about an inch.A chain that's too short or tangled won't allow the flapper to close and water will continue to leak into the bowl. This causes the fill valve to cycle on and off to refill the tank. A chain that's too long, or a flush rod that hits the the tank lid, won't open the flapper wide enough to stay open for the full flush. You'll find yourself having to hold the lever to complete a good flush.
To avoid these problems, adjust the linkage in the chain to leave only a slight bit of slack when closed. Cut the chain at the rod to leave only about an inch extra to reduce the potential for tangles. Then put the tank lid back on and make sure the flush rod doesn't strike the lid when you press the lever. If it does, bend it down slightly and readjust the chain.
Replace the flapper

Change the flapper

Unsnap the old flapper and take it with you to the store to find an exact replacement. In addition to the closest replacement, pick up a "universal" type.If you've completed the first three steps and your toilet keeps running, chances are you have a worn-out flapper. Turn off the water, remove the old flapper and take it to the store to find an exact replacement. (Hardware stores often carry a wide variety.) Most flappers snap over ears on the overflow tube. Others have a ring that slips over the tube.
Now here's the catch. You may not find an exact match. The range of flapper styles has mushroomed over the last 15 years, and you may find 15 to 20 flapper options on the store shelf. Some packages include specific brand and model information (so note yours before you leave home). Others have a "universal" label. If you can't find an exact replacement, try the closest one and pick up a universal type as well. They're cheap, and the extra one just might save you a second trip to the store! (Avoid the "adjustable" types unless you're replacing an adjustable one.)
Install the new flapper and make sure it opens and closes freely. Then test it. If the toilet keeps running or runs intermittently, you're not getting a good seal. Try a different flapper if the toilet won't stop running.
If you just can't find a flapper that seals, consider replacing the entire overflow tube/flapper. On most toilets (two-piece), this means removing the tank. It's not difficult and you don't need special tools. It'll take you about an hour, and you'll avoid that expensive plumber service call.
if you go to this link it will show you step by step on how to fix it. How to Stop Running Toilet Family Handyman

check the overflow pipe in the cistern tank as some fill valves do not stop completely but allow input of water after the noise has stopped. This allows the water level to rise up and the water to flow out into the toilet bowl. Reduce the water level height by adjusting the cut off level and when the water rises past the new level the increase pressure on the valve will shut it off.

If the flapper and all has been replaced. then it must be worn out where the flapper sits. or its not smooth.check to make sure it is smooth where the flapper closes, and make sure it closes fully when flushed. you might be better off with a new toilet, but thats up to you!

Toilet runs continuously or doesn't flush adequately

Jiggling the handle might work for a while, but if your toilet is always running or doesn't flush adequately, you need to perform these simple fixes that usually can tame a noisy, inefficient toilet.

Check the Chain

The chain attached to the rubber flapper often becomes loose, causing incomplete flushing and/or continuous running. To fix it, remove links from the chain using needle-nosed pliers until it's tight.

Check Water Level

Improper water levels can also cause problems with your toilet. This can be fixed by adjusting the ball ****, which is located next to the overflow pipe, the open tube to the right of the handle. Adjust the ball **** so the water comes to ½ " below the overflow pipe.

Clean the Surface of the Flush Valve

A continuously running toilet can also be the result of a faulty flush valve. Because the valve is made of rubber, it can decompose or warp allowing water to escape from the tank into the bowl. Clean the sealing surface to see if this will improve the seal. If too decomposed or warped the valve may need to be replaced.

Replace the Flapper

Remove old flapper and replace with a suitable replacement. Attach the flapper to the overflow pipe inside the bowl. Then attach the lever chain from the flapper to the handle lever making sure the chain is taut.

This video will help familairaize you with the flushing mechanism and the repair:

The Kohler Cimarron is one of the most popular and reliable toilets out there. (My Favorite). However, depending on the hardness of the water and if you use cleaner tabs in the tank, these factors can lead to a malfunction.
The first thing you should do is hold the flapper (rubber seal inside the tank that releases the water down to the bowl) down with your hands for a few seconds after a flush and see if the toilet stops running. Sometimes the flapper doesn't seal properly therefore the fill valve keeps working non stop. Stopping the fill while holding the flapper down will confirm that your flapper needs to be changed.
If this doesn't work then try this....
The other common problem with a running toilet is with the fill valve itself. There is an attached float on the fill valve that goes up and down depending on the water level. Once the water level rises, it rises the float, and the float tells the fill valve to stop filling the tank. While the toilet is running (hissing), try raising the float all the way up with your hand and see if it stops. If it stops but not consistently with every attempt, then you will need to change the fill valve. I believe the Fluidmaster 400A is the replacement model.

fill valve not shutting off water running over overflow tube set or replace fill valve flapper valve leaking replace flapper valve cracked and leaking flush valve assembly replace

As long as there is no water leaking from the tank to bowl connection, you are OK. You would know if it was leaking here, because you would have water dripping out onto the floor.

Verify that the water level in your tank is below the top of your new flush valve's overflow tube. If the water level comes to the top, it will overflow into the toilet bowl. This can be easily fixed with an adjustment to the fill valve.

If the water is not overflowing into this tube, then the only way you can lose water is through the flapper. You said you changed the flush valve, which would have come with a new flapper attached to it, but maybe buy a new flapper and see what happens???

Check the fill tube in your toilet one easy way to see if it's leaking is get food coloring and pour in your tank to color the water this makes it easier to see and squeeze the tube in the tank when it's full if you see the colored water running down the middle of it you have a winner! if not you can look around for it sometimes the plastic under the flapper gets cracked too

Sounds like your flapper is leaking causing the water in the tank to lower until it triggers the fill valve. Replace the flapper (they're cheap and wear out easily).

the fill valve shut off level setting is too high. water in the tank is overflowing in the overflow tube. adjust fill valve to shut off at lower tank level