Ok, so I've had my bike for a short while now and have read up lots of stuff, even fixed my first flat (tube) and patched up the tire that I documented in this post (the tire was actually damaged due to being run flat/or a blowout, the rims (one edge) were slightly damaged (looks like it was run on the ground, had some gouge all around one side of rim) too which I have filed down and fixed).

I've got a problem that I am not sure what it is. I believe I've had it since acquiring the used bike. Basically, when I peddle hard in whatever gear, I hear a sound, like a creek. If I turn my bike upside down and peddle with my hand, I don't hear anything. If I peddle without much pressure (torque) with my feet, I don' hear anything. I've already changed my peddles so that's not it (changed from clip less to platform). Any help to diagnose and fix the issue is appreciated thank you.