T4 BRAKES ASE: LATEST 2025 WITH QUESTIONS AND CORRECT VERIFIED ACCURATE
ANSWERS (A+) GUARANTEED PASS
Psi loss rate for Straight Truck - (ANSWER)2 psi/minute
Psi loss rate for combination vehicle - (ANSWER)less than 3 psi/minute
Service Brake Pressure Drop Test - (ANSWER)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 - (ANSWER)Cause
1) brake imbalance
2) increased stopping distance
3) excessive heat and wear
Instability and premature wear - (ANSWER)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 - (ANSWER)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 - (ANSWER)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.
1
, T4 BRAKES ASE: LATEST 2025 WITH QUESTIONS AND CORRECT VERIFIED ACCURATE
ANSWERS (A+) GUARANTEED PASS
5) may be attached to compressor or externally mounted.
Air Compressors - (ANSWER)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" - (ANSWER)1) tank closest to the compressor.
2) "pop off valve" located on this tank to keep from over pressuring the system.
Pop-off valve - (ANSWER)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 - (ANSWER)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 - (ANSWER)1) used to keep condensation out of the system using a desiccant material to
remove moisture.
2
2
ANSWERS (A+) GUARANTEED PASS
Psi loss rate for Straight Truck - (ANSWER)2 psi/minute
Psi loss rate for combination vehicle - (ANSWER)less than 3 psi/minute
Service Brake Pressure Drop Test - (ANSWER)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 - (ANSWER)Cause
1) brake imbalance
2) increased stopping distance
3) excessive heat and wear
Instability and premature wear - (ANSWER)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 - (ANSWER)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 - (ANSWER)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.
1
, T4 BRAKES ASE: LATEST 2025 WITH QUESTIONS AND CORRECT VERIFIED ACCURATE
ANSWERS (A+) GUARANTEED PASS
5) may be attached to compressor or externally mounted.
Air Compressors - (ANSWER)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" - (ANSWER)1) tank closest to the compressor.
2) "pop off valve" located on this tank to keep from over pressuring the system.
Pop-off valve - (ANSWER)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 - (ANSWER)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 - (ANSWER)1) used to keep condensation out of the system using a desiccant material to
remove moisture.
2
2
