Posted on April 21, 2022 by Jack PACCAR MX-13 – Loosening poly-V-belt 8PK 1. Move the tensioner (1) against the spring force and lock it with a 4 mm thick pin (A). Use only a hexagonal socket or a hexagonal ring spanner. 2. Take the poly-V-belt (2) off the idler pulley first and then off the belt pulleys.