What's your shop IQ?

Posted on June 1, 2005

The National Institute for Automotive Service Excellence (ASE) offers a series of school bus-specific tests as part of its certification program. The school bus exam categories include body systems and special equipment (S1), diesel engines (S2), drive train (S3), brakes (S4), suspension and steering (S5), electrical/electronic systems (S6) and air conditioning systems and controls (S7).

The following questions were drawn from the ASE’s test catalog. The next round of certification tests will be offered in mid-November. For more information about ASE or to register for the fall tests, visit

1. An air-operated stop arm will not fully extend. Which of these is the most likely cause?
(A) Low air pressure
(B) Binding hinge pivots
(C) A sticking solenoid valve
(D) A broken return spring pivot

2. On a Type C school bus, the defroster blower works on low and medium speed, but not on high speed. The most likely cause is a:
(A) bad circuit breaker
(B) bad control switch
(C) loose ground
(D) clogged heater filter

3. The driver complains that the school bus will not crank. The most likely cause is:
(A) loose starter bolts
(B) an open vandal lock circuit
(C) a shorted starter ground cable
(D) the gear selector left in neutral

4. During a cold-weather start-up, the oil filter ruptures, causing an oil leak. This could be caused by:
(A) a stuck-closed oil filter bypass valve
(B) a stuck-open oil pressure regulator valve
(C) use of a high-viscosity motor oil
(D) excessive engine rpm at start-up

5. A Type A school bus with an overdrive transmission and a computer-controlled lock-up converter has shifts that are early and very soft. The most likely cause is:
(A) an improperly adjusted throttle valve cable (B) a slipping converter clutch
(C) a worn governor gear
(D) a shorted converter clutch solenoid

6. The rear axle in a Type C school bus is noisy on deceleration. Which of these is the most likely cause?
(A) A worn ring and pinion
(B) A worn carrier bearing
(C) A bad front pinion bearing
(D) A bad rear pinion bearing

7. A school bus has an uneven braking problem. Which of these could be the cause?
(A) A binding treadle (foot) valve
(B) Low brake line air pressure
(C) A bad brake drum
(D) A bad governor

8. The driver of a school bus with air brakes says that it has poor stopping power. All of these could be the cause EXCEPT:
(A) the quick-release valve exhaust port is plugged
(B) the air pressure is too low
(C) the application line is restricted
(D) the brakes are adjusted wrong

9. Excessive steering wheel freeplay may be an indication of:
(A) a loose power steering pump drive belt
(B) improperly adjusted axle stops
(C) contaminated power steering fluid
(D) loose steering sector-to-frame mounting bolts

10. The windshield wipers on a school bus will not park. Which of these is the most likely cause?
(A) The worm gear is out of adjustment
(B) A bad parking switch assembly
(C) A binding wiper transmission
(D) A poor ground at the wiper motor

(Answers on next page) {+PAGEBREAK+} ANSWERS: 1. (A) 2. (B) 3. (B) 4. (A) 5. (A) 6. (C) 7. (C) 8. (A) 9. (D) 10. (B)

Comments ( 1 )
  • BeeBopEh

     | about 3 years ago

    I drive a 2007 IC bus (365DT 8cyl with 137,000 km or 72,000 miles). The wipers go into an intermittent problem where they go into steady regular speed wiping, BUT the the steering wheel stalk multi-switch is "off". Pulling out the electrical panel wiper relay stops them. This still happens after our mechanics have installed a new wiper relay cube, a new wiper motor and a brand new steering wheel stalk multi-switch. Does anybody have and idea where the wiring short or glitch might be? Many thanks if anybody has seen this one or you can pass along a hint on solving this one.

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