Five ASE T8 Preventive Maintenance Inspection (PMI) practice test questions, answers included.

1. Recall · Engine Systems

   A truck's cooling system is filled with propylene glycol coolant. Which of these gives a reliable reading of its freeze protection?

   1. A refractometer read on its propylene glycol scale
   2. A float hydrometer made for ethylene glycol coolant
   3. A pH test strip dipped into a coolant sample
   4. A refractometer read on its ethylene glycol scale
   Show the answer

   A. Correct. A refractometer reads how strongly the coolant bends light, and the same reading means a different freeze point for propylene glycol than for ethylene glycol, so the tool carries a separate scale for each. Read on the scale for the glycol in the system, it gives the freeze point directly.

   Why not the others

   B. A float hydrometer works from specific gravity, and propylene glycol mixtures are lighter than ethylene glycol mixtures of the same strength, so a hydrometer scaled for ethylene glycol misreads them. Use a refractometer on its propylene glycol scale.

   C. A pH strip shows whether the coolant has turned acidic or too alkaline; it says nothing about glycol concentration or freeze point. Freeze protection is read with a refractometer on the scale for the coolant's glycol type.

   D. The same refractometer reading means a different freeze point for propylene glycol than for ethylene glycol, so reading propylene glycol coolant on the ethylene glycol scale gives the wrong freeze point. Use the scale that matches the coolant.

   ID T8-A-001 · Task T8-A-24 (ASE task list)

2. Recall · Cab and Hood

   A truck has a manual pull-type clutch with mechanical linkage and a clutch brake. At a PMI, the clutch pedal is pushed slowly by hand from its fully released position to measure its free travel. Where does the free travel end?

   1. Where the clutch brake begins to squeeze
   2. Where the release fork meets the bearing
   3. Where the clutch fully releases the disc
   4. Where the linkage's lost motion is taken up
   Show the answer

   B. Correct. Free travel is the pedal movement that closes the gap between the release fork and the wear pads on the release bearing housing; once the fork meets the pads it starts pulling against the pressure plate springs, and pedal effort rises sharply. That distance is compared with the maker's specification and recorded.

   Why not the others

   A. The clutch brake is squeezed only in the last part of the stroke, after the clutch has released, and that point is checked separately. Free travel ends much sooner, where the release fork reaches the wear pads on the release bearing housing and pedal effort rises.

   C. The clutch fully releases only after the fork has pulled the bearing through its release travel, well past the end of free travel. Free travel ends where the fork first meets the release bearing's wear pads.

   D. Lost motion in worn linkage pivots is taken up early in the stroke and only adds to free travel; the fork still has its gap to close. Free travel ends where the fork meets the release bearing's wear pads.

   ID T8-B-006 · Task T8-B-25 (ASE task list)

3. Recall · Electrical/Electronics

   During the PMI of a battery-electric truck that charges from an AC charging station, the inspector traces the high-voltage path from the charge port to the traction battery pack. Which component converts the incoming AC to DC to charge the pack?

   1. The DC/DC converter
   2. The power electronics controller
   3. The onboard charger
   4. The charge port
   Show the answer

   C. Correct. The onboard charger takes the AC that arrives through the charge port and converts it to DC to charge the traction battery pack. It is part of the high-voltage system, so it and the cables joining it to the port and the pack are inspected as live components, by look and by the manufacturer's procedure, never by touch.

   Why not the others

   A. The DC/DC converter steps the traction battery pack's high-voltage DC down to the low-voltage DC that runs the accessories and recharges the 12-volt auxiliary battery. It does not take in the charging station's AC; the onboard charger does.

   B. The power electronics controller manages the energy the traction battery pack delivers to the traction motor, controlling the motor's speed and torque. Turning the charging station's AC into DC for the pack is the onboard charger's job.

   D. The charge port is only the connection to the external power supply: it passes the AC in but does not convert it. The onboard charger, downstream of the port, converts the AC to DC for the traction battery pack.

   ID T8-C-003 · Task T8-C-1 (ASE task list)

4. Recall · Frame and Chassis

   What does the clutch brake on a heavy truck's non-synchronized manual transmission do?

   1. It stops the input shaft so a gear can go in at a standstill
   2. It slows the input shaft so upshifts go faster on the move
   3. It holds the truck still when the clutch is let out on a grade
   4. It keeps the release bearing from spinning with the pedal up
   Show the answer

   A. Correct. With the pedal floored, drag in the released clutch keeps the input shaft and countershaft spinning, which grinds the teeth of a non-synchronized gear. In the last part of pedal travel the release bearing squeezes the clutch brake against the transmission and stops them, so first or reverse engages cleanly with the truck stopped.

   Why not the others

   B. The clutch brake is meant for the stopped truck only. Pressing the pedal to the floor during an upshift while moving loads the clutch brake against a turning driveline and wears or burns it out; moving shifts are timed with engine and road speed instead.

   C. Holding the truck on a grade is the job of the service and parking brakes. The clutch brake acts only on the transmission input shaft, and only while the pedal is near the floor with the clutch released.

   D. With the pedal up, the release bearing turns with the clutch and is clear of the clutch brake. The clutch brake comes into play only at the end of pedal travel, when the bearing clamps it to stop the input shaft.

   ID T8-D-001 · Task T8-D-30 (ASE task list)

5. Recall · Frame and Chassis

   During a PMI, the S-camshaft bracket bushings of a truck's air brakes are greased through their fittings. When has enough grease been pumped into a bushing?

   1. When new grease purges at the slack adjuster end
   2. After a set number of strokes, whatever shows
   3. When grease shows inside the drum at the cam head
   4. When the gun resists and will not pump more
   Show the answer

   A. Correct. The bracket bushing is greased until new grease purges from the seal at its slack adjuster (inboard) end, which shows fresh grease has filled the bushing. The seal at the camshaft head end is there to keep grease away from the brake linings, and the amount needed varies, so the purge, not a stroke count, is the sign to stop.

   Why not the others

   B. A fixed stroke count may stop short of filling the bushing, or may push grease past the camshaft head seal toward the linings. The bushing is greased until new grease purges at the slack adjuster end.

   C. Grease at the cam head inside the drum has passed the seal that keeps it off the linings; that seal is replaced, the grease cleaned off the cam head and rollers, and contaminated linings replaced. Greasing stops when new grease purges at the slack adjuster end.

   D. Hard resistance means a blocked fitting or passage, not a full bushing. The fitting is cleared or replaced and greasing continues until new grease purges at the slack adjuster end.

   ID T8-D-042 · Task T8-D-20 (ASE task list)

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