Psi loss rate for Straight Truck correct answers 2 psi/minute
Psi loss rate for combination vehicle correct answers less than 3 psi/minute
Service Brake Pressure Drop Test correct answers Apply service brake to 90 psi. Loss rate should be less than 3 psi/minute for straight vehicles and less ...
T4 ASE Brakes || Already Graded A+.
Psi loss rate for Straight Truck correct answers 2 psi/minute
Psi loss rate for combination vehicle correct answers less than 3 psi/minute
Service Brake Pressure Drop Test correct answers Apply service brake to 90 psi. Loss rate
should be less than 3 psi/minute for straight vehicles and less than 4 psi/minute for combination
vehicles.
Improperly adjusted brake shoes correct answers Cause
Instability and premature wear correct answers a 4 psi difference in the air delivery between
axles is enough to cause instability and premature wear.
Troubleshooting poor brake performance due to air correct answers 1) inspect air compressor
2) verify pressure build up
3) look for clogged air compressor filter
4) possible slipping belt
5) possible air leaks
6) possible defective governor
Pressure Governors correct answers 1) regulates air going to system
2) adjustable pressure
3) defective governor or out of adjustment can cause compressor to function improperly.
4) designed to regulate the compressors output.
5) may be attached to compressor or externally mounted.
Air Compressors correct answers 1) Power is transferred to the air compressor by either an
internal gear or by an external belt. Belt is most common.
2)air can be drawn directly from the atmosphere through a filter.
3) Pistons push the air through a discharge valve to the supply reservoir.
Supply Reservoir "Wet Tank" correct answers 1) tank closest to the compressor.
2) "pop off valve" located on this tank to keep from over pressuring the system.
Pop-off valve correct answers Also known as the pressure relief valve, exhaust valve, adjustable
pressure limiting (APL) valve, or overflow valve; this valve is the point of exit of excessive
pressure buildup before damaging air components.
, Manual and Automatic Drain Valves correct answers 1) installed in each reservoir/tank to help
purge the system from moisture.
2)Used in high humid or wet climates.
3) manual drain valves should be drained on a daily basis
Air Dryer correct answers 1) used to keep condensation out of the system using a desiccant
material to remove moisture.
2
Air Compressor troubleshooting correct answers 1) can develop air leaks and pass oil into the
brake system which will cause poor braking and or grabbing or dragging.
2) clogged air intake filter will cause slow pressure build up.
Compressor oil checks correct answers 1) engine oil should be checked for compressors that get
lubrication from engine.
2) Oil sump compressors have their own oil reservoirs and should be checked daily.
Compressor Pressure Testing correct answers 1) with engine running at idle; air pressure should
build from 85-100 psi within 45 seconds.
2) if the engine is running at full governed rpm; pressure should build within 25 seconds and the
compressor should maintain a constant pressure of 100-120 psi.
Troubleshooting air leaks correct answers 1) if no leaks are found check to see if dirty air filter is
restricting the intake of the compressor.
Gear Driven Compressor correct answers 1) must be meshed with the timing gear on the engine
before installation. A misaligned gear can cause poor pressure buildup.
2) Compressor timing can be achieved by aligning the timing marks on the gear and crankcase.
Governor Diagnosing correct answers To check with engine running: let system fill to about
125psi. Slowly reduce air in system by apply and releasing the air brakes. Observe the pressure.
At about 100 psi the pressure should rise indicating the governor is cutting in and out at proper
psi.
Check for leaks by applying soapy water at exhaust vent valve. Leakage in excess of 3 inch soap
bubble indicates replacement of governor.
Adjusting governor correct answers 1) before adjusting governor, check the accuracy of the
gauge with a test gauge.
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