Tractor protection valves:
A wig-wag (low air warning device) should operate:
An inversion/spring brake modulating valve must be mounted upside down.
The Canadian Motor Vehicle Safety Standards (CMVSS) schedule 121 states that parking brakes must hold an empty or loaded vehicle on a:
Spring brakes commonly operate the _________________ to keep the vehicle from moving when parked.
Cracking pressure" of relay valves refers to:
Which section of the foot valve is used as the primary section?
The CMVSS section 121 states that a visual low air warning device must be located in the drivers forward field of vision.
What is the style of valve often called a "highway valve"?
On a dual air system, a tractor protection valve uses which of the following?
An ideal air braking system can be defined as:
All of the following could cause excessive leakage in an air brake system (service brakes applied) EXCEPT:
If the load and speed of a unit are both doubled, the effort needed to stop is _________ times.
Where would you expect that a quick-release valve would be mounted?
Technician A says that a frozen, plugged, or crimped discharged line from the air compressor and before the air dryer may cause an air compressor to blow the head gasket. Technician B says that a frozen, plugged or crimped discharged line from the air compressor and before the air dryer may cause the compressor to make a knocking sound. Who is correct?
You are performing an air timing balance test on a combination vehicle. Technician A uses an accurate watch as part of the required equipment. Technician B says that balanced air timing means each axle receives air at the same time and at the same pressure level as needed by the driver. Who is right?
The dual circuit foot valve:
What style of air valve would be used on a trailer without spring brakes?
When the tractor park control valve pops out.
A driver communicates a complaint of dragging brakes, Technician A says a leaking diaphragm or seal could cause the problem. Technician B says a broken return spring in the service brake section could be the cause. Who is right?
What does the double check valve do?
On an air brake system, the maximum allowable build up time for a single unit (tractor only) between 50 and 90 PSI is:
Tests of brake applications and stroke length are made at _________ minimum air pressure at the brake chamber.
Technician A says that the park and emergency braking system is a distinct air circuit, separate from the regular service brake system. Technician B says that spring brake chambers use air pressure in the opposite way from the service brake chambers. Who is right?
What is brake compounding?
Air line gladhand seals are made of:
How many ports does a typical relay valve have for a tandem axle?
What does the tractor protection valve do?
A heavy truck brake system is being inspected. Technician A says that the proportioning valve should be inspected every time the brakes are serviced. Technician B uses gauges ahead of and behind the proportioning valve to test its function. Who is right?
What is a rule that applies equally to almost all air brake systems?
Why is it very difficult to have the same actuation pressure on all axles of a combination vehicle?
During a brake inspection, a technician tests the air supply system. After doing a complete visual and audible examination, finds only that the air system build-up time is slow. Which one of the following could be the cause?
When testing the operation of the trailer hand control valve, a technician should:
When diagnosing a service brake relay valve, all of the following apply EXCEPT:
When considering the proper operation of a tractor service brake relay valve:
Technicians are discussing quick-release valves. Technician A says that a bad tractor protection valve will cause wheel lockup on the tractor during a brake application. Technician B says a defective quick-release valve can cause a slow front application pressure buildup and reduce stopping ability. Who is right?
Technicians are diagnosing the tractor spring brake control valve. Technician A says if the rear axle reservoir is drained to zero air pressure and the brake application valve is applied, the tractor air brake pressure should be at 120 psi. Technician B says when the tractor parking brakes are applied, the air pressure at the tractor spring brake valve delivery port should drop quickly to zero. Who is right?
Technician A says that the trailer air supply valve allows air to enter the trailer brake system when its knob is pushed inward. Technician B says that the knob of the park control (system park) valve must be pulled out before the trailer air supply valve can receive air at the control port. Who is right?
Technician A says that pressure below 45 psi in the air brake system will cause the knob of the trailer air supply valve to pop out. Technician B says that the pressure below 45 psi in the trailer air brake system will cause the control valve inside the tractor protection valve to close. Who is right?
When testing brake application valve leakage, Technician A says that the brake application pressure should be 90 psi (553.6 Kpa). Technician B says that this test is done every 50,000 miles. Who is right?
When conducting operation and leakage tests on single and double check valves:
What does a bobtail proportioning valve do?
Which statement below is correct regarding what the trailer spring brake valve does?
A relay valve:
A driver complains that all the air brakes on his truck are dragging. Where would you look for the problem?
The relay emergency have is found on:
Modulated spring brake systems are used for parking.
Blended air is the mixing of primary air and secondary air.
Relay valves are located close to the foot valve.
On air brake systems, pedal travel rather than pedal pressure regulates the brake application force.
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