The gasket around the flush valve probably is the problem. It must seal to the bowl when the toilet is flushed. The bolts are not affected by flushing action and if leaking,will do so even if the toilet is untouched for hours. Extra tightening is not ordinarily a good idea.

There are a few different versions of the gasket( fat and soft,thin and soft,fat and firm,thin and firm) although you will only frind one or two at big box stores. Like so most things, experience shows if gasket is correct when tank rests on bowl with the right gap before tightening bolts. Big box gaskets are usually very soft and thicker than nessary. If over compressed,the gasket is squeezed from between coupling. Assuming that's what's happening,try shimming between tank and bowl. The shim material needs to be about 3/8ths thick -- + ,flat and about the consistancy of the rubber washer on flush valve you replaced earlier. The preferred consistancy is one which you can only slightly compress between thumb and index finger. Evenly shim all four corners and do not over tighten bolts. Just snug enough tank can only be rocked fore and aft 1/2 inch with one finger,not rock at all side to side with any less force than applied with palms pressing on top of tank. If there is more than 1/4tr inch between tank lid and wall,shim there also to prevent leaning back and rocking tank eccessivly. On the other hand if tank is tight against wall (unable to create gap with pressure of one finger) it may be cock-eyed at coupling which makes over/under tightening even more unforgiving. Idealy there is a gap between wall and tank but little or none between lid and wall, Only if you ask,I'll tell you why cussing helps.

Thanks for your help. I thought about shimming, but I was afraid I would make matters worse. There is about a 1/4 inch gap between the lid and the wall. There is no play at all when I try to move the tank. The tank will leak continuously as long as there is water in it. It's not a big leak, a slow drip of about one drop every 2-3 seconds, from the bolts.

The part of the bowl where the tank sits has two parallel ridges built into the porcelain. I thought the tank had to rest on those two ridges, so by your explanations, it seems that I was overtightening a lot. Thanks.

For a quick and sure repair, try to follow this steps:

- Stopped the water to the can.

- Flush the can, and after that wipe out the water staying in the tank. Imperative: Be certain to take out any blocks, jugs, little water art, or fish that may stay in the tank.

- Disengage the channel tube at the can, not at the shutoff. In the event that you disengage the tube at the shutoff pressure fitting, there is to a lesser degree a risk that you will have the capacity to reuse the line later. Take a gander at the line itself. On the off chance that it is chromed and has a washer on the top, you ought to attempt to get a substitution washer when you go to the tool shop.

Here is a link that might be useful: lubrication pumps

You are correct about tank resting on two ridges "if you had a gasket identical to origional". I suggest you only snug the bolts down being carful to keep them even by going back and forth while tightening them. If it leaks,tighten bolts 1/2 turn each until leak stops then 1 more turn.