New Bathroom Faucet Leaks After an Hour

Help me! I have completely run out of patience and ready to call in a pro.

I replaced my bathroom sink faucet, Kohler, which came with a new drain stopper. After fiddling around I got everything installed correctly. Or so I thought.

I can run water, fill up the basin and drain it, no problem and no leaks. 5 minutes, no problem. 20 minutes, no problem.

But an hour later, running nothing through the sink, I develop a leak from what appears to be coming from the connection between the basin and the top of the drain underneath.
Can anyone tell me what's going on?

We would need to know how you installed the drain assembly to answer your question.

It's the same ol same oh.
Did you put putty or pipe dope on the threads near the top between the body of the drain and the rubber donut?
And I mean, just the threads.

Are you sure it is NOT the 1 1/4" tailpiece? Did you use a thread sealant when you screwed it into the drain fitting?

Terry, you're right. I'm sure you guys hear all the same incomplete questions from us newbies all the time and I apologize.

I followed the pictures in the installation booklet to a T, which doesn't tell you hardly anything at all. I used plumbers putty underneath the chrome drain plug on top of the sink surface. I screwed the drain pipe assembly directly into that plug, using NO pipe dope or white tape thread sealant on the threads above that rubber grommet. The installation book only shows plumbers putty, so that's probably my problem.

Will try that. Thanks for your patience guys.