A leaking piston pump is rarely just a seal problem—it’s usually a mismatch between pump specifications, seal materials, and real working conditions. This guide explains why piston pump seals fail in off-road machinery, how to correctly identify pump models and build codes, and how to select a compatible seal kit that actually solves the leak instead of repeating it. From material selection and groove measurement to common resealing mistakes, this article helps equipment owners and technicians reduce wrong orders, prevent repeat failures, and restore hydraulic performance with confidence.