Free ASE Transit Bus Diesel Engines (H2) Examination Practice Questions

Sample Practice Questions

Try these 10 sample questions from the ASE Transit Bus Diesel Engines (H2) Examination practice bank. Each includes the answer and explanation. Continue with the interactive practice above to review the full question set.

1. 1A Series 40 diesel engine is tested at maximum no-load speed with the specified breather restrictor tool installed. What is the highest crankcase pressure permitted by its guide?

   1. A.3 in. water (0.75 kPa)
   2. B.6 in. water (1.5 kPa)Correct answer: B
   3. C.9 in. water (2.25 kPa)
   4. D.12 in. water (3.0 kPa)

   Explanation: The Series 40 guide specifies "6 in. water (1.5 kPa)" as the upper limit under these test conditions. The question asks for the maximum, so a lower acceptable pressure is not the limit.

   Reference: Series 40 Operator's Guide (6SE240) — 9.21 Item 21 – Crankcase Pressure

2. 2A removed diesel cylinder head must be checked for mating-surface roughness before a new head gasket is fitted. Which instrument directly measures this surface-finish property?

   1. A.A dial indicator
   2. B.A precision straightedge
   3. C.A profilometerCorrect answer: C
   4. D.An outside micrometer

   Explanation: Fel-Pro identifies a surface-finish comparator or "a profilometer". Flatness, lift, and thickness measurements do not directly measure the microscopic roughness required for this gasket check.

   Reference: Fel-Pro Tech Tips — How To Prepare An Engine Surface For Gasket Installation — p. 1, Determining the Proper Finish, surface-finish measurement bullet

3. 3Bearing ink is applied to a diesel block's liner-flange seat. A new liner is pressed onto the seat without gaskets and removed. The transferred ink is uneven around the circumference. What does Motorservice's check indicate?

   1. A.The liner seat needs reworking to restore proper contact.Correct answer: A
   2. B.The seating surface is acceptable because some ink transferred.
   3. C.The head bolts should be overtorqued to force full seat contact.
   4. D.Extra liquid sealant should be used to replace the missing contact.

   Explanation: Motorservice requires the contact surface to be "evenly coated with ink". An uneven transfer calls for seat reworking, not acceptance based on partial contact, extra bolt torque, or sealant.

   Reference: Motorservice — Cylinders and Cylinder Liners Part 1 — Torn-off flange on the cylinder liner, Note — bearing-ink check

4. 4In a diesel lubrication system, why may a full-flow filter's bypass valve open when cold oil or a loaded element creates excessive restriction?

   1. A.To stop lubrication until the filter is replaced
   2. B.To keep oil flowing to the engine despite the restrictionCorrect answer: B
   3. C.To provide finer filtration through an auxiliary kidney loop
   4. D.To return all pump output to the sump before it reaches the bearings

   Explanation: Donaldson describes the valve as protecting against "oil starvation". Temporary bypass keeps oil reaching the engine despite restrictive media. Stopping lubrication or returning all output to the sump would starve the bearings; fine filtration in an auxiliary kidney loop is a different function.

   Reference: Donaldson — Full-Flow vs. By-Pass Lube Filtration: Key Differences Explained — The Role of By-Pass Valves

5. 5A Series 40 dry-type air-cleaner element has been in service for 14 months, but has not reached the maximum restriction limit. What does its guide's replacement rule require?

   1. A.Keep it until the restriction limit is reached, regardless of age.
   2. B.Keep it until the engine develops visible exhaust smoke.
   3. C.Clean it with fuel and restart its service-age count.
   4. D.Replace it because the one-year service limit has passed.Correct answer: D

   Explanation: Replacement is required "after one year of service" or at maximum restriction, whichever occurs first. Passing the calendar limit is sufficient even when restriction remains acceptable.

   Reference: Series 40 Operator's Guide (6SE240) — 9.9.1 Air Cleaner Replacement

6. 6Which sensor is disconnected before the crank-and-prime cycles in the specified Series 40 fuel-priming procedure?

   1. A.Engine coolant temperature sensor
   2. B.Camshaft position sensorCorrect answer: B
   3. C.Manifold absolute pressure sensor
   4. D.Engine oil pressure sensor

   Explanation: The procedure says "Disconnect the CMP (camshaft position sensor)" before the priming cycles to prevent engine startup. Coolant-temperature, manifold-pressure, and oil-pressure sensors are not the specified disconnect.

   Reference: Series 40 Operator's Guide (6SE240) — 10.5.2 Prime the Fuel System and Start the Engine, step 1

7. 7A transit-bus battery shows an acceptable no-load voltage after surface charge is removed, but the engine still cranks poorly. What additional battery assessment is needed before calling the battery healthy?

   1. A.A load test to evaluate performance while delivering currentCorrect answer: A
   2. B.A second identical no-load reading as proof of capacity
   3. C.The manufacturer's printed CCA rating without a performance test
   4. D.Clean terminals alone as proof that the battery can supply cranking current

   Explanation: Fluke states that voltage tests indicate "state of charge, not the battery condition". A load test checks performance while current is demanded. Repeating no-load voltage, reading the CCA label, or finding clean terminals does not establish present cranking capability.

   Reference: Fluke 98 Automotive ScopeMeter Series II — Users Manual — p. 5-79, Electrical System, Battery Test, Measuring System Voltage

8. 8During investigation of an engine-related vibration on a Series 40-powered transit bus, the mounting bolts are secure. Which additional mount inspection does the engine guide call for?

   1. A.Inspect the mounting pads directly for deterioration or damage.Correct answer: A
   2. B.Infer pad condition solely from the mounting bolts being tight.
   3. C.Accept the pads if the engine develops normal power in service.
   4. D.Judge pad condition solely from alignment of the bolt witness marks.

   Explanation: The guide separately requires checking the "condition of the mounting pads". Bolt security, normal power, and unchanged witness marks do not establish the condition of the pads themselves.

   Reference: Series 40 Operator's Guide (6SE240) — 9.20 Item 20 – Engine and Transmission Mounts

9. 9When specifying the resurfacing finish for a diesel cylinder head, which approach follows Fel-Pro's gasket-installation guidance?

   1. A.Use the same finish for every gasket material and design.
   2. B.Match the finish to the required gasket and applicable specifications.Correct answer: B
   3. C.Choose the smoothest possible finish regardless of gasket requirements.
   4. D.Choose the roughest finish the machine can produce to increase grip.

   Explanation: Fel-Pro states, "Different gaskets require different surface finishes". Both excessive roughness and excessive smoothness can create sealing problems; one universal finish or either extreme is not the selection rule.

   Reference: Fel-Pro Tech Tips — How To Prepare An Engine Surface For Gasket Installation — p. 1, Determining the Proper Finish

10. 10A wet diesel cylinder liner has cavitation pits on its coolant-facing surface. Which mechanism describes the material removal identified by Motorservice?

    1. A.Chemical corrosion dissolves metal without bubble collapse.
    2. B.Collapsing vapor bubbles produce impacts that remove particles.Correct answer: B
    3. C.Solid abrasive particles scrape the coolant-facing metal surface.
    4. D.Freezing coolant expands and fractures the coolant-facing surface.

    Explanation: Motorservice explains that vapor "bubbles implode" and the resulting impacts remove liner material. Chemical dissolution, abrasion by solids, and freeze expansion are different damage mechanisms rather than cavitation.

    Reference: Motorservice — Cylinders and Cylinder Liners Part 1 — Cavitation on cylinder liners, Damage assessment