HEAVY TRUCK BRAKES MICHIGAN

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HEAVY TRUCK BRAKES MICHIGAN

MECHANIC STUDY GUIDE

UPDATED ACTUAL EXAM WITH

CORRECT SOLUTIONS.

an engine brake (jacobs brake) - correct answer- a. is a self- energizing servo type.

• is normally used in place of a spring brake.
• restricts the intake port and causes a build up of 30-45 lbs of

pressure.

• opens the exhaust valves near the top of the compression

stroke to release the compressed air. (correct awnser)

in the system shown below, the part at c is: - correct answer- a.

an inversion valve. (possible correct awnser)

• a safety valve.
• a modulator valve. (not correct awnser)
• a relay valve.

a mechanic has removed a brake drum and found the brake

linings soaked with grease. the brake linings should be: -

correct answer- a. replaced. (correct awnser)

• sanded to roughen up the friction surface.
• dipped in lacquer thinner. 1 / 3

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• washed with denatured alcohol.

in the drawing below, the parking brakes are applied by: -

correct answer- a. air pressure at point f.

• vacuum in area b.
• spring at point c.
• pressure in area a. (not correct awnser)

what is the purpose of a vacuum booster? - correct answer- a.to decrease brake pedal effort. (possible correct awnser)

• to prevent fade under heavy braking.
• to provide assistance when the engine vacuum is low. (not

correct awnser)

• to maintain uniform pedal travel as the linings wear.

the trailer brakes do not work. the tractor system is at normal pressure. there are no leaks and the service and emergency lines are hooked up right. what could cause this problem? - correct answer- a. ice in the lines at the trailer.

• a bad relay valve.
• a bad safety relief valve.
• both a and b. (correct awnser)

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the residual valve in the master cylinder: - correct answer- a.

limits pressure build up in the system.

• stops the flow to damaged brake lines.
• keeps some pressure in the sytem when the brakes are

released. (correct awnser)

• is operated by engine vacuum.

higher than normal air pressure would likely be caused by: -

correct answer- a. a govenor that is bad or out of adjustment.(possible correct awnser)

• a plugged safety valve. (not correct awnser)
• a one-way check valve stuck open.
• a sticky quick release valve.

if gladhand 2 is unhooked or has a severe leak, what will happen during operation? - correct answer- a. valve at a will protect the pressure in the dry tank.

• tractor brakes will apply automatically. (not correct awnser)
• valve at c will apply trailer brakes.
• valve at b will apply trailer brakes.

during a hard stop, one brake has locked on a trailer with "s" cam brakes. the service and emergency lines are hooked up properly and the system is at normal pressure but the brakes

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