Agricultural Equipment Technician (425A) — Red Seal

Performs common occupational skills

What identifies the strength grade of a metric hex-head fastener used on agricultural equipment?

1. The colour of the zinc plating applied at the factory on the affected unit
2. The thread pitch stamped on the side of the head
3. Numeric class markings such as 8.8 or 10.9 on the head
4. The radial line count used for inch-series fasteners

Metric fasteners carry a property class on the head — common values include 8.8, 10.9 and 12.9 — where the first number relates to tensile strength and the second to the yield-to-tensile ratio. Plating colour describes the corrosion coating, not strength, and varies by supplier. Thread pitch describes geometry but does not indicate the mechanical capability of the steel. Radial dash marks identify SAE inch-series grade and do not apply to ISO metric fasteners, so they cannot be used on a metric joint that has the class number stamped on its head.

RSOS 2021 | A-2.06 Uses fasteners, sealants, adhesives and gaskets

Diagnoses and repairs engines and engine support systems

A tractor cooling system loses coolant with no external leak visible. Which test should the technician perform first?

1. Replace the radiator cap and refill the system with new coolant
2. Block-test the coolant for combustion gases using a chemical indicator
3. Drain the engine oil and inspect the pan for water contamination
4. Run the engine at full load and watch the temperature gauge response across the equipment

A combustion-gas block test uses a chemical indicator drawn over the coolant; a colour change confirms exhaust gases are entering the coolant through a head-gasket or cracked-head path. Replacing the cap blindly addresses one possible leak point but skips the diagnosis. Inspecting the pan finds coolant in oil only after migration is already severe. Running at full load can accelerate the failure and risks warping the head before the cause has been confirmed at low risk.

RSOS 2021 | B-6.03 Diagnoses cooling systems

Diagnoses and repairs drive trains

What is required when installing a new dry clutch disc?

1. Apply chassis grease to both sides of the disc to prevent squeak
2. Hand tighten the pressure plate bolts and let the engine seat them carefully on the unit
3. Use the alignment tool and torque the pressure plate to the manufacturer specification
4. Heat the pressure plate before installation to ease alignment

An alignment tool centres the disc on the pilot bearing while the pressure plate bolts are torqued in sequence to the manufacturer specification; this ensures the input shaft engages on first installation. Grease on the friction surface causes immediate shudder and slip. Hand-tightened bolts allow the cover to walk under spring force and warp. Heating the pressure plate anneals the diaphragm spring and changes the clamping load.

RSOS 2021 | C-9.01 Repairs dry clutches