CEM Technical Skills & Application 2 — Questions and Answers
Question 1: When a hydraulic cylinder on a piece of heavy equipment exhibits rod seal leakage, what is the FIRST corrective action a CEM should take?
- Replace the entire hydraulic cylinder assembly
- Inspect the rod surface for scoring or pitting before replacing seals (Correct answer)
- Add hydraulic fluid to compensate for the leak
- Increase system pressure to overcome the seal failure
Correct answer: Inspect the rod surface for scoring or pitting before replacing seals
A scored or pitted rod will destroy new seals immediately, so the rod condition must be assessed before any seal replacement.
Question 2: Which electrical principle is most important when troubleshooting a voltage drop issue in a heavy equipment starting circuit?
- Kirchhoff's Current Law
- Ohm's Law applied across each circuit segment (Correct answer)
- Faraday's Law of Induction
- Lenz's Law
Correct answer: Ohm's Law applied across each circuit segment
Ohm's Law (V=IR) allows a technician to measure voltage drop across each connector and cable segment to locate high-resistance faults.
Question 3: A track-type tractor experiences excessive final drive oil temperature. Which condition is LEAST likely to be the cause?
- Plugged final drive breather
- Worn final drive bearings
- Low engine coolant level (Correct answer)
- Overfilled final drive oil level
Correct answer: Low engine coolant level
Engine coolant level does not directly affect final drive oil temperature because final drives are not cooled by the engine cooling system.
Question 4: What is the purpose of the load-sensing signal line in a modern hydraulic system?
- It sends pump outlet pressure to the operator display
- It communicates actual load pressure to the pump compensator to match flow demand (Correct answer)
- It bypasses excess flow to the tank when demand is low
- It signals the engine ECM to increase RPM under hydraulic load
Correct answer: It communicates actual load pressure to the pump compensator to match flow demand
The load-sensing line transmits work-port pressure back to the variable-displacement pump compensator, allowing it to produce only the flow and pressure the load requires.
Question 5: When performing a scheduled undercarriage inspection on a crawler dozer, which measurement BEST indicates overall undercarriage wear status?
- Track shoe bolt torque
- Track pitch elongation percentage (Correct answer)
- Idler flange height
- Carrier roller diameter
Correct answer: Track pitch elongation percentage
Track pitch elongation percentage directly reflects pin-and-bushing wear and is the primary metric for determining remaining undercarriage life.
Question 6: A wheel loader's automatic transmission fails to upshift under load. After confirming adequate transmission fluid level and condition, what is the NEXT diagnostic step?
- Rebuild the transmission clutch pack
- Check the transmission electronic control module for fault codes (Correct answer)
- Replace the torque converter
- Perform a stall test to evaluate engine output
Correct answer: Check the transmission electronic control module for fault codes
Modern powershift transmissions use electronic controls; retrieving fault codes identifies whether the issue is solenoid, sensor, or mechanical before invasive repairs.
Question 7: Which lubrication film type is present in a properly functioning sleeve bearing operating at rated speed and load?
- Boundary lubrication
- Mixed-film lubrication
- Full hydrodynamic lubrication (Correct answer)
- Elastohydrodynamic lubrication
Correct answer: Full hydrodynamic lubrication
At rated speed and load, a sleeve bearing develops a full hydrodynamic wedge of oil that completely separates journal and bearing surfaces.
CEM Technical Skills & Application 2
When a hydraulic cylinder on a piece of heavy equipment exhibits rod seal leakage, what is the FIRST corrective action a CEM should take?