I know this may be the most asked question in the biking world, but here I come again. I recently purchased a garbaged road bike that I (almost) restored. One of the many things I did was replacing a threaded BB with a sealed Shimano one (BB-UN 300).
Testing it I noticed that when standing up or applying high force, it starts clicking with every stroke.
Then, after watching a thousand videos and reading a thousand forums, everyone agrees with using a big amount of grease, so I reinstalled it cleaning everything, and regreasing (nicely) the threads, and where the 'cup' half couples with the long half of the BB (this was not greased before). Installed and tightened alternating from side to side until I could no longer tighten each side, installed the crank arms (cleaned and lightly greased the tapers), and same with the bolts (clean and apply grease to the threads) and tight until they were all the way in and could not tighten more.
The problem is still there, and I may think that the square holes in the crank arms are worn out. I think the crank assembly (minus the new BB) are the bike originals and are rivetted, so no loose crank bolts.
I mention this because I read that either the square spindle or the crank hole can wear out and not make a good contact, leaving a gap that can make the spindle move inside the hole; and to discard a worn spindle (it may have less than 10km, so no time to wear out).
I could try to save the crank by using a thin piece of tinfoil to try to 'fill' the gap that there may exist.
A useful post that covers this.
I once had a MTB that had this exact problem. Loose crankarm bolt, destroyed square spindle and no possibility to save it, so the BB had to be replaced.
Maybe I could use some threadlocker in the crankarm bolts after trying to add the tinfoil to ensure the stay tight?
Thanks in advance.