Exam 31: Air Brake Servicing

You test governor cut-out pressure to be exactly at specification but governor cut-in is too low.What should you do FIRST?

Technician A says that when a supply reservoir is completely drained,air pressure in the primary circuit should drop to zero.Technician B says that when the secondary reservoir is completely drained,pressure in the primary reservoir should drop to zero.Who is correct?

You are replacing a spring brake chamber on a truck drive axle with a one with a pushrod that must be cut to size.Which of the following MUST be performed to properly fit the new spring brake chamber?

Where does the governor sense air pressure?

Technician A says that when testing the performance of a dual circuit foot valve,it is normal to measure about 2 psi (14 kPa)higher pressure in the outbound primary circuit than in the outbound secondary circuit.Technician B says that warped trailer air disc brake rotors can cause foot valve chatter during service applications.Who is correct?

Which of the following would NOT be justification for tagging a vehicle in OOS (Out Of Service)?

How often should truck air tanks be drained during normal operation?

Technician A says that when you observe excessive slack adjuster pushrod travel,the slack adjuster is probably over-adjusting.Technician B says that an over-adjusting slack adjuster must be replaced.Who is correct?

What is the current maximum stopping distance for an FMVSS 121 compliant tractor trailer rig that is unloaded?

When an ABS equipped tractor is coupled to a non-ABS trailer,which of the following would likely result from a panic service brake application?

Technician A says that a frozen relay valve supplying the tractor drive axle brakes can cause the brakes not to release.Technician B says that a frozen relay valve can cause service brakes not to apply.Who is correct?

Technician A says that a truck with an FMVSS-121 air system must have a minimum of three air reservoirs.Technician B says that some FMVSS-121 compliant trucks use a single tank,divided internally into three reservoirs.Who is correct?

What brake diagnostic tool is used to measure the change in angle of a truck chassis when it is subjected to aggressive braking?

When you are using visual stroke indicators to assess slack adjuster stroke,which of the following is required?

How fast are the wheels turned on a diagnostic brake dynamometer?

Technician A says that if the electrical supply to an air dryer is interrupted,the dryer purge valve will immediately cease to function.Technician B says that the heater used in many air dryers is cycled by a thermostat.Who is correct?

Technician A says that most truck compressors today are seldom rebuilt in the field today.Technician B says that it most cases it is cost effective to rebuild compressors in the shop rather than stock rebuilt/exchange units.Who is correct?

Which of the following tests is commonly used by roadside enforcement officers to quickly verify that a truck air supply system is performing to CVSA standards?

Assuming a major air leak in tractor-trailer combination that will result in complete system air pressure loss,which of the following sequence of events will occur FIRST?

If the air compressor does not have an intake adapter,how often is it recommended that you should service its air cleaner filter element?