For many years on threaded items that pass liquids (brake fluid, coolant, engine oil) in cars, trucks and motorcycles, I've used a pipe thread sealant with TFE to lubricate and seal the threads. I've also had good success using on home plumbing.
Now I find myself with a few newly installed NPT fittings that leak a little here and there despite my careful prep and tightening. I tightened them pretty good, without over tightening them, as there were already pretty tight. Making them tighter (afraid to crack it), they still leak.
Am I doing something wrong or using the wrong pipe sealant?