Thank you (whoever that may be) in advance for any advice you can offer. I truly appreciate any suggestions you may have in helping me get to the bottom of this.

When I flush my toilet, air bubbles enter the tank through the drain hole. I do not see any bubble whatsoever in the bowl, only in the tank. These bubbles result in the flapper being held open for too long and the toilet flushing once and then sort of "half-flushing" again. The toilet doesn't overflow, but then, I'm not putting anything in it when I flush.

Upon flushing, the bowl doesn't drain immediately... it fills up an extra couple of inches and then eventually does the one-and-a-half flush routine.

The toilet in the other bathroom operates just fine. Waste and all. It doesn't back up, there aren't any bubbles in the tank... it operates normally.

Blessings and thanks again in advance,
Brian

It turns out that I had the supply valve turned up too high. When I cut the flow of water in half the air bubbles went away. But, I continue to have issues with this toilet. When I use the sink, I hear the toilet take in a little more water to the tank. Any recommendations?

Thanks again.

[ When I use the sink, I hear the toilet take in a little more water to the tank.]
First let me explain what's happening. Water does not compress. That's why we install air chambers to absorb the shock and to prevent "water hammer".
When you shut your lavatory faucet off, if the air chambers aren't working, it sends a shock back up the line. Your toilet being on the same branch receives this shock at the ball cock. This shock will jiggle the float ball up and down and kick the water on for a second until the shock passes. To check what I'm saying take the tank lid off and watch the float ball when the turn the cold water off and on at the lavatory. Your air chambers are waterlogged and need to be recharged. Let me show you how.
Back in the 60's we were required to to put shock absorbers,(air chambers) on all bath lavatorys and kitchen sinks. Over time water and condensate built up in them and they must be recharged. First turn off the house at the main house shut off valve. Then open hot and cold faucets at the farthest bathroom to prevent air lock.(This is important.) You will find under each fixture little brass or chrome valves. These are called angle stops. With a small pail held under the angle stop to catch the run off look under the handle of the stop and you will see a nut with the stem running through it. This is called the bonnet packing nut. Put your wrench on it and back it off counterclockwise. Now open the stop and remove the stem and washer assembly, The stop will begain to drain. When it has quit draining reassemble the stop and move on to the next one. Do this on each one of your angle stops. There will be six of them. When you are done, close off the faucets you have opened, turn on the water to the house, and give yourself a pat on the back.
You have just recharged your air chambers and saved yourself a hefty service call bill. Good luck, TOM

Thanks so much! I'll be sure to give this a try and let you know how it turns out. Even now that I've figured out the air bubble thing, this toilet still flushes slower and with less force than my other commode. Could recharging the air chambers fix this? Or is it likely that I have a clog in addition to needing to recharge?

Thanks again,
Brian

{this toilet still flushes slower and with less force than my other commode. Could recharging the air chambers fix this?}
No, but check this out. I have one that most repair plumbers miss.. Look down at the bottom of the bowl. If there is a small hole, then that is a jet that starts the syphon action. If it's clogged the water will be slow in flushing. Take your finger,(UGH! ) and run it around the inside of the opening. Over the years minerals build up and cut down on the syphon (flush) action. If it is rough or you feel build up, take a table knife and put a bend in it to get around the curve in the bowl and chip and scrap it clear. Next take a coathanger and clear out the holes around the rim. They start the swirling action. And last, check the water level in the tank. It should be 1/2" below the top of the over flow tube. And speaking of the overflow tube, Make sure the small 1/8" tube from the ballcock to the white overflow tube is connected so it discharges in it and that it's flowing when the ballcock fills. This is what raises the water level in the bowl. For a good solid flush they all have to work together. Good luck, Tom

The hole at the bottom of the bowl was being obstructed by minerals. After cleaning out that hole as well as the holes along the rim of the bowl, the toilet is now working wonderfully.

Thanks so much for your help! So, to any novices that may stumble upon this thread in the future, learn from my experience:

1. Turn your supply valve down about 50% if you see bubbles in the tank or if your flapper stays up for too long

2. Use a clothes hanger to clean the holes along the rim of the bowl and at the bottom of the bowl

3. Never use a hand auger in your toilet