ASE H8 Preventive Maintenance & Inspection (Transit Bus) flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

DVIR retention period

Driver vehicle inspection reports must be kept by the carrier for three months from the date of the report, per 49 CFR 396.11.

Annual inspection interval

Every commercial vehicle requires a documented inspection at least once every 12 months, and the inspection report is retained for 14 months.

Brake inspector qualification

Under 49 CFR 396.25, only a qualified inspector who has passed an appropriate test may inspect, repair, or adjust a vehicle's brakes.

Whichever-comes-first PM trigger

Preventive maintenance is due when mileage, calendar time, or engine hours reaches its set limit first, not when all three limits align.

DEF concentration

Diesel exhaust fluid must be 32.5 percent urea by weight meeting ISO 22241; it freezes near 12 F and has a limited shelf life.

Air filter restriction limit

Replace the engine air filter when the restriction indicator reaches the manufacturer's limit, which is commonly about 25 inches of water.

Coolant freeze point

A 50/50 coolant mix protects to about minus 34 F and raises boiling point; verify the mixture with a refractometer at each PM.

V-belt deflection rule

On a V-belt, correct tension typically allows about one-half inch of deflection at the midpoint of the longest span under moderate thumb pressure.

Transmission fluid check

Check automatic transmission fluid with the engine running, transmission in neutral, parking brake set, and fluid at normal operating temperature.

U-joint inspection

With the driveline chocked and free to turn, grasp each U-joint and check for radial play, missing snap rings, and rust-colored dust.

Driveshaft yoke phasing

Driveshaft yokes at both ends must be aligned in the same plane; incorrect phasing causes a vibration that cycles once per shaft revolution.

Differential oil level

Check gear oil at the fill plug hole with the vehicle level; lubricant should be even with the bottom of the hole, not overflowing.

Governor cut-out pressure

The air compressor governor cuts out, stopping compression, at roughly 100 to 125 psi depending on the vehicle's published specification.

Static air leak limit

With the system fully charged, the engine off, and brakes applied, pressure loss must not exceed 3 psi per minute on a single vehicle.

Low air warning threshold

A warning buzzer and light must activate before system pressure drops below 60 psi, alerting the driver before spring brakes apply.

Brake lining minimum

Bonded brake lining is condemned at about one-quarter inch thickness, or when a rivet head is within one-sixteenth inch of the friction surface.

Steer tire tread minimum

Front steering axle tires must have at least 4/32 inch of tread depth, while tires on all other axles require at least 2/32 inch.

Steering free play limit

Steering wheel free play, measured before the tires begin to move, must not exceed 10 degrees on a 20-inch diameter steering wheel.

Air suspension ride height

Ride height is measured between specified frame and axle points and must match the manufacturer's specification before a wheel alignment is performed.

Recaps on steer axle

Retreaded or recapped tires are prohibited on the front steering axle of a bus; only new tires may be installed there.

Battery open circuit voltage

A fully charged 12-volt battery reads about 12.6 volts at rest, while 12.2 volts indicates roughly 50 percent state of charge.

Charging voltage range

A 12-volt charging system should hold about 13.8 to 14.5 volts at the battery with the engine running and loads applied.

Turn signal flash rate

Turn signal lamps must flash between 60 and 120 times per minute, which equals one to two flashes per second.

Parasitic draw test

With all accessories off, doors closed, and control modules asleep, current draw should remain below the manufacturer limit, typically around 50 milliamps.

Refrigerant recovery rule

Under EPA Section 608, R-134a must be recovered and recycled with certified equipment; intentionally venting refrigerant to the atmosphere is prohibited.

Vent temperature check

A properly charged bus air conditioning system typically delivers center vent air about 35 to 45 F below the ambient temperature.

Evaporator condensate drain

A clogged evaporator drain causes water to overflow inside the coach; the drain tube is cleared and flow-verified at each PM.

Wheelchair securement points

ADA requires four tiedown points plus a lap and shoulder belt; each anchorage is rated and inspected for wear and secure mounting.

Oil sample procedure

Draw the sample mid-drain from a warm engine into a clean container to avoid idle-time contamination and obtain a representative wear reading.

Coolant test strips

Test strips read nitrite, pH, and freeze point; results outside the published specification indicate depleted additives and require coolant service.

TES 295 fluid rule

Allison automatic transmissions specify TES 295 approved fluid; mixing with unapproved fluid can cause clutch slippage and shortened transmission life.

Lockout tagout rule

Before servicing, isolate every energy source, apply locks and tags, and verify zero energy, including stored air pressure and electrical disconnects.