Help -- Toilet STILL Leaking...

About a month ago a $90 water bill told us that we had a leak somewhere. We tracked it to an upstairs toilet that had a slow leak. I have no idea what the toilet model is -- it came with the house. (built in the 1970s). The first thing I did was change the flapper, but that didn't help.

DETAILS:

• There is no water on the floor or between the tank and bowl.
• If you turn the water source off, the tank will empty in about 5-7 minutes.
• We put food coloring in the tank and confirmed that the water is leaking from the tank into the bowl.

Tonight I used a Fluidmaster Universal Complete repair kit to replace the Fill Valve and Flush Valve (I took the tank off and followed all instructions to replace all gaskets, washers, etc.). I have confirmed that there is no water leaking outside the tank and the brand-new flapper is snug.

But it's still leaking!  ARRRRRRGH! I cannot articulate how ticked off I am right now.

I really don't want to call a plumber, but I may have to unless someone here can give me a suggestion on what to do next.

Any help you guys can give me will be greatly appreciated.

Shut the water off, empty the water out of the water closet ( the part that fills with water). Using a small piece of a plastic bag wrap it around where the water goes town to the toilet bowl and rubber band it tight. Fill the water closet back up with water. Is the problem still there.?

If not, take the bag off. Make sure the the rubber flapper is making full contact by placing your fingers around it and pushing down to seal it against the the lip of the hole. Is the problem still there.? replace, if not...

Remove the water closet, make sure the gasket that's between the water closet and bowl is secure. This should be a plastic piece that screws to the bottom of the water closet and should be screwed tight. This is the piece that the flapper rest on to stop the water from going into the bowl. 

replace the Fill Valve and Flush Valve, it may help to resolve it

I already did that. That's why I'm so upset. 

Elsewhere, a guy suggested I use plumbers putty around the flush valve to provide an extra seal. I just did that and am now doing another food coloring test. I will report back with the results.