Pre-Trip Inspection: Hydraulic Brakes
4 questions in the bank cover this topic. Everything below is drawn from the sources those questions cite.
Sources: 49 CFR 570.55
What you need to know
A pedal that keeps sinking under steady force means fluid is escaping somewhere, past a seal or out of a line.
A firm pedal is a sealed system.
no perceptible decrease in pedal height under a 125-pound force applied to the brake pedal
49 CFR 570.55
80 percent, which leaves reserve travel for a second application or for worn linings.
A pedal already near the floor has nowhere left to go when you need more brake. None of the figures offered is the one the rule gives.
When the brake pedal is depressed with a force of 50 pounds, the distance that the pedal has traveled from its free position shall be not greater than 80 percent of the total distance from its free position to the floorboard
49 CFR 570.55
570.55(d) names all of them.
Contact with the chassis is a defect before any damage appears, because the rubbing is what produces the chafing you would otherwise wait to find.
Hydraulic brake hoses shall not be mounted so as to contact the vehicle body or chassis. Hoses shall not be cracked, chafed, or flattened.
49 CFR 570.55
Any leakage at all.
The master cylinder is where every brake application starts, so a leak there affects the whole system rather than one wheel.
Master cylinder shall not show signs of leakage.
49 CFR 570.55
Check yourself
- What is required under 125 pounds of force on a hydraulic brake pedal?
- What is the maximum travel of a hydraulic brake pedal under 50 pounds of force?
- What is a hydraulic brake hose defect?
- At the master cylinder you are looking for ______.
Answers are in the practice test for this topic.