When greasing brakes, it’s important to grease the brake to capacity. Putting in less grease than is needed to fill all interior gaps can lead to condensation forming inside the brake components, which may cause rust and corrosion. Seals inside the cam tube are engineered to let excess grease out of the area, meaning new grease should be added until any dirty grease or condensation is visibly purged out of the end cam tube near the slack adjuster.
Grease purging at the opposite end of the cam tube, near the S-cam head, indicates a bad grease seal that must be replaced. Grease purged at the cam head can drop into the brake drum, contaminating the drum and lining, and impacting brake performance.