A cement plant reported that a XCMG ZL50GN wheel loader's rear wheels were extremely hot after operation, and the machine felt like it was "driving with the brakes on." The operator had to press the accelerator hard to reach 20 km/h.
The technician first jacked up the rear axle. The wheels were hard to turn by hand. He checked the brake calipers. The brake fluid was black and contaminated. He removed the rear brake caliper pistons. The pistons were seized in the "Engaged" position. The contamination in the brake fluid (due to moisture absorption) had caused the pistons to rust and stick. This caused the constant dragging and heat.
Furthermore, he checked the "Differential Housing Breather Cap." The breather cap was plugged with cement dust. The differential heats up during operation, expanding the internal air. If the breather is plugged, the pressure builds up. This pressure pushed against the "Axle Shaft Oil Seal," forcing differential oil into the brake housing. The oil contaminated the brake pads, reducing braking efficiency, while the heat from the dragging brakes overheated the entire axle.
The repair involved honing the brake caliper bores, replacing the pistons and seals, and flushing the brake lines. The differential breather cap was cleaned with solvent. The axle was drained and filled with new gear oil. The machine then rolled freely, and the axle temperature stayed within normal limits.
