Here’s a stimulating quiz on school bus maintenance issues to share and discuss with your shop team. Topics covered include valve timing, air brakes and hard starting.
The questions were supplied by David Anderson, the director of transportation and fleet service at Adams 12 Five Star Schools in Thornton, Colorado, who has extensive maintenance experience. Since he started his pupil transportation career in 1981, Anderson has also served in the positions of mechanic, shop foreman and fleet manager. (Scroll down below all seven questions to see the answers.)
1. Technician A says that incorrect valve timing could result in harsh, late shifts on an automatic transmission that uses a vacuum modulator. Technician B says that this condition would create soft, early shifts. Which technician is correct?
A. A only
B. B only
C. Both A and B
D. Neither A nor B
2. A universal joint has prematurely failed. The failure was drastic enough that the bars on the cross are cracked almost all the way through. The most likely cause is:
A. Improper lubrication maintenance
B. Over-torqued U-bolt retaining nuts
C. Too much load (excessive vehicle weight combined with much driving on upgrades) carried over a long period
D. Contamination of lube due to deteriorated seals, which in turn causes binding
3. The driver of a school bus with air brakes says that the brakes are slow to release. Which of the following is the least likely cause?
A. Weak return springs
B. A plugged exhaust port
C. A kinked air line
D. Worn brake linings
4. A school bus with a two-piece driveshaft exhibits drivetrain vibration that is noticeable only in the lower gears when accelerating fairly hard. Technician A says the driveshaft is worn and needs to have the U-joints replaced to smooth out their motion. Technician B says the problem is very likely to be related to either poor design of the suspension or worn bushings. Who is right?
A. A only
B. B only
C. Both A and B
D. Neither A nor B
5. A diesel engine is hard starting. Which is the least likely cause?
A. Incorrect oil for the ambient temperature
B. Low cetane fuel
C. Defective turbocharger
D. Engine speed or timing signal not present due to damaged sensor
6. Technician A says an electronically controlled lock-up torque converter could cause the engine to stall at stops. Technician B says a centrifugal lock-up torque converter requires no outside controls. Which technician is correct?
A. A only
B. B only
C. Both A and B
D. Neither A nor B
7. Technician A says that when moving or adding wheelchair tie-down track to the floor of a bus, lag bolts are acceptable as long as they go through the steel subfloor. Technician B says that all tie-downs have to meet the same specs and are interchangeable with parts from other manufacturers. Who is right?
A. A only
B. B only
C. Both A and B
D. Neither A nor B
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