Final answer:
To check the free play of manual slack adjusters on S-cam brakes, the vehicle should be parked on a level, hard surface with wheels chocked, and the parking brakes released. Free play should not exceed one inch at the push rod.
Step-by-step explanation:
To check the free play of manual slack adjusters on S-cam brakes, you should park on a level, hard surface to ensure that the vehicle doesn't move during inspection. Ensure that the parking brakes are released, and the wheels are chocked to prevent any movement. Free play is typically checked by applying force to the slack adjuster until there is movement at the push rod. The amount of free play allowed can vary by manufacturer, but typically it should not be more than one inch (25 mm) at the push rod. Excessive free play can indicate that the slack adjuster needs adjustment or that there are other issues in the brake assembly that need attention.