Evaluation and Testing Process Flashcards

A technician is evaluating a truck's engine using a diesel exhaust fluid (DEF) quality sensor. A DEF concentration reading of 25% urea is detected. The acceptable range is:

Answer: 32.5% ± 1.5% urea by weight

SAE and OEM specifications require DEF to contain 32.5% urea by weight (±1.5%), so 25% is out of range and will trigger a SCR system fault.

When evaluating transmission output shaft end play on a heavy-duty manual transmission, excessive end play will MOST likely cause:

Answer: Oil leakage past the output shaft seal and possible bearing failure

Excessive output shaft end play allows the shaft to move axially, wearing and eventually destroying the rear bearing and causing oil seal failure.

During evaluation of a coach's door system, pneumatically operated doors open slowly but close at normal speed. The MOST likely cause is:

Answer: A restricted or maladjusted opening-direction flow control valve

Pneumatic door systems use directional flow control valves to regulate speed; restriction in the opening circuit slows only opening motion.

A technician evaluates a truck frame for cracks using magnetic particle inspection. This method is MOST effective for detecting:

Answer: Surface and near-surface cracks in ferromagnetic materials

Magnetic particle inspection reveals surface and near-surface discontinuities in ferromagnetic metals; it is not effective on non-ferrous materials or deep internal flaws.

When evaluating a diesel engine's turbocharger, axial play (thrust) beyond specification is MOST likely to cause:

Answer: Oil leakage into the intake and exhaust due to seal wear

Excessive axial play allows the turbocharger shaft to move beyond seal limits, causing oil to be ingested into the intake or expelled into the exhaust.

During a truck electrical system evaluation, a technician finds battery voltage is 12.1V with the engine off and all loads disconnected. This state-of-charge indicates approximately:

Answer: 50% charged

An open-circuit battery voltage of approximately 12.1V corresponds to roughly 50% state-of-charge for a 12V lead-acid battery.

When performing a final quality control evaluation after a major engine overhaul on a Class 8 truck, which test is performed LAST before returning the vehicle to service?

Answer: A controlled break-in road test following the OEM break-in procedure

After verifying mechanical integrity with bench tests, the break-in road test under controlled load conditions is the final step to seat rings and verify all systems under actual operation.