Originally Posted by
BCRider
Even with the loose balls solution at best you're just buying time. The balls will thunk past the brinneled wear mark and damage themselves a lot sooner than normal. The eventual flat spots on the balls will wear away at the rest of the bearing race and soon the whole set will need replacing anyway.
But if you do go with fully packed loose balls it'll likely last the rest of this season unless you typically rack up thousands of miles a season.
Also the likely cause of the issue, assuming it's not a split headset race, is too LITTLE preload when it was set up. They should be set tight enough that you can feel a little drag in the headset. Not "cogging" tight but a little tighter than it was when the play first wasn't there.
Damage is from fretting. It's lubrication failure. There's fore-and-aft motion in the steerer (typically road vibration), and no rotation (except when you steer). this depletes the film of oil on the balls, which produces lots of friction, which produces heat, which welds the parts together microscopically, and then they're ripped apart. Getting the pre-load right certainly helps prevent the damage from fretting, but it's hard to get right if there's already damage.