2
T4 ASE Brakes Exam with accurate detailed solutions
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Psi loss rate for Straight Truck - ✔✔2 psi/minute
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Psi loss rate for combination vehicle - ✔✔less than 3 psi/minute
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Service Brake Pressure Drop Test - ✔✔Apply service brake to 90 psi. Loss rate should be less
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than 3 psi/minute for straight vehicles and less than 4 psi/minute for combination vehicles.
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Improperly adjusted brake shoes - ✔✔Cause || || || || ||
1) brake imbalance
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2) increased stopping distance
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3) excessive heat and wear
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Instability and premature wear - ✔✔a 4 psi difference in the air delivery between axles is
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enough to cause instability and premature wear.
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Troubleshooting poor brake performance due to air - ✔✔1) inspect air compressor || || || || || || || || || || ||
2) verify pressure build up
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3) look for clogged air compressor filter
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4) possible slipping belt
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5) possible air leaks
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6) possible defective governor
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, 2
Pressure Governors - ✔✔1) regulates air going to system
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2) adjustable pressure
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3) defective governor or out of adjustment can cause compressor to function improperly.
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4) designed to regulate the compressors output.
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5) may be attached to compressor or externally mounted.
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Air Compressors - ✔✔1) Power is transferred to the air compressor by either an internal
|| || || || || || || || || || || || || || ||
gear or by an external belt. Belt is most common.
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2)air can be drawn directly from the atmosphere through a filter.
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3) Pistons push the air through a discharge valve to the supply reservoir.
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Supply Reservoir "Wet Tank" - ✔✔1) tank closest to the compressor.
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2) "pop off valve" located on this tank to keep from over pressuring the system.
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Pop-off valve - ✔✔Also known as the pressure relief valve, exhaust valve, adjustable
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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 - ✔✔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
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T4 ASE Brakes Exam with accurate detailed solutions
|| || || || || || ||
Psi loss rate for Straight Truck - ✔✔2 psi/minute
|| || || || || || || ||
Psi loss rate for combination vehicle - ✔✔less than 3 psi/minute
|| || || || || || || || || ||
Service Brake Pressure Drop Test - ✔✔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 - ✔✔Cause || || || || ||
1) brake imbalance
|| ||
2) increased stopping distance
|| || ||
3) excessive heat and wear
|| || || ||
Instability and premature wear - ✔✔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 - ✔✔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
|| || ||
, 2
Pressure Governors - ✔✔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 - ✔✔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" - ✔✔1) tank closest to the compressor.
|| || || || || || || || || || ||
2) "pop off valve" located on this tank to keep from over pressuring the system.
|| || || || || || || || || || || || || ||
Pop-off valve - ✔✔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 - ✔✔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
|| || || || || || || || || ||
