Not confident there is a convenient fix to this particular problem. In a tiled shower/bathtub, I have leaking faucet, I removed handle and related fixture. Then discovered that previous owner (or sloppy plumber or sloppy tiler) somehow covered access to valve with Thinset (mortar). There's mortar on the brass valve, too. Obviously difficult to identify the valve or cartridge that needs to be replaced. Does anybody know a delicate way to remove Thinset? It's a small area.