A heavy electric counterbalance forklift with a wet?disc brake axle was reported as "creeping on the grade with the park brake applied." The park brake would hold on flat ground, but on a slight ramp the truck would slowly roll. The brake stack had been adjusted, but the creep persisted.
We pulled the axle dipstick and the oil was milky-water contamination. The vent cap was missing, and wash?down water had entered the housing. Over time, the water had degraded the oil and rusted the surface of the brake plates. The friction material had also glazed from slipping in the contaminated oil, reducing the static friction coefficient.
We drained the oil, flushed the housing with clean fluid, and replaced the brake plates. We also installed a new vent cap and briefed the customer not to pressure?wash the axle area. After the flush and plate replacement, the park brake held solid on the ramp. On wet?brake axles, any sign of milky oil or water in the housing should trigger a brake inspection, not just an oil change.
