If you are checking and adjusting automatic slack adjusters and don't have an application pressure gauge, turn the engine off and step on and off the brake pedal to reduce air pressure to
- 100–110 psi
- 90–100 psi ✓
- 80–90 psi
- 70–80 psi
Answer: B. 90–100 psi
With no application pressure gauge, pump the reservoir pressure down to 90–100 psi before making a full brake application.
Why this is the answer
The handbook says most automatic slack adjuster manufacturers want pushrod stroke checked with a 90 to 100 p.s.i. application. If you lack an application pressure gauge, the same section tells you to shut the engine off and pump the reservoir down into that 90 to 100 p.s.i. range, then make a full application. That is why the bank answer matches the 90–100 psi choice.
Why the other answers are wrong
- A. 100–110 psi — 100–110 psi is above the manufacturer's application range given for checking pushrod stroke, so it is not the pressure to pump down to.
- C. 80–90 psi — 80–90 psi falls below the 90–100 psi application range stated for checking pushrod stroke.
- D. 70–80 psi — 70–80 psi is lower than the stated 90–100 psi range for making the full application.
Remember it
Picture the gauge-free method as landing inside the 90–100 psi window before you apply the brakes fully.