weeping rear brake lines
The primary reason I know of these is my HVAC service. Schrader valves are traditionally a 1/4 SAE flare, and when you put a dust cap on them the dust cap "should" have a flare washer inside. 99.99% of them don't, and if they are tightened very much at all, the cap will damage the flare fitting and make removing the Schrader core (tire valve) difficult or impossible
These kind have a rubber o ring and are "finger tight"
However, most these hex caps (typically OEM) don't, and if overtightened, "are" a problem
The primary reason I know of these is my HVAC service. Schrader valves are traditionally a 1/4 SAE flare, and when you put a dust cap on them the dust cap "should" have a flare washer inside. 99.99% of them don't, and if they are tightened very much at all, the cap will damage the flare fitting and make removing the Schrader core (tire valve) difficult or impossible
These kind have a rubber o ring and are "finger tight"
However, most these hex caps (typically OEM) don't, and if overtightened, "are" a problem