Trade Practical Skills and Workshop/Lab Procedures
Domain 2 examines whether you can carry out workshop jobs in a safe, repeatable sequence: isolation, dismantling, inspection, repair, reassembly, adjustment and functional test. Examiners look for method, not speed.
Core procedures
- Open a job card before work; identify the machine, complaint and isolation method (key off, battery isolated, pressure relieved, implement lowered).
- Clean before dismantling; cap fuel, hydraulic and air lines; bag and label fasteners.
- Follow the service manual's tightening sequence and torque values. Cylinder heads are usually tightened from the centre outwards in stages.
- Replace gaskets, seals, O-rings and stretch bolts where specified; never reuse a crushed gasket.
- After assembly, check fluid levels, rotate by hand where possible, then run and leak-test before release.
Worked example
A four-cylinder head has a torque specification of 40 N·m, then 80 N·m, then a final 110 N·m, in a centre-out spiral. You set the torque wrench to 40 N·m and tighten in sequence, repeat at 80 N·m, then 110 N·m. Reasoning: staged tightening spreads clamping load and avoids warping the head; one-pass final torque can crush the gasket unevenly. Recheck that the wrench is calibrated and that threads are clean and lightly oiled only if specified.
Traps
Using a pipe extension on a torque wrench changes the applied torque; tightening from the outside in; reusing head bolts that are torque-to-yield; forgetting to refit dowels; starting an engine before restoring oil pressure.