Mazda MX-5 NA silhouetteMX-5 NA

BRAKE SYSTEM

P-13prose procedure
Continued from P-12

POWER BRAKE UNIT

Quick Inspection, On-vehicle

Power brake unit function check (Simple method)

Step 1

  1. 1
    With the engine stopped, depress the pedal a few times.
    Two ignition switches side by side (ACC, ON, START, LOCK positions). Left: hand pressing brake pedal with downward arrow; right: starting engine while pedal is depressed.
    05U0PX-021
  2. 2
    With the pedal depressed, start the engine.
  3. 3
    If immediately after the engine starts the pedal moves down slightly, the unit is operating.

Step 2

  1. 1
    Start the engine and let it run 1 or 2 minutes.
    Two circles: O (left, OK) and X (right, NG). Hand pressing brake pedal with labels FIRST, SECOND, THIRD showing successive strokes becoming shorter on the OK side; constant stroke on the NG side.
    05U0PX-022
  2. 2
    Stop the engine.
  3. 3
    Depress the pedal with the usual force.
  4. 4
    If the first pedal stroke is long and becomes shorter with subsequent strokes, the unit is operating.
  5. 5
    If a problem is found, inspect for damage or improper connection of the check valve or vacuum hose. Repair if necessary, and inspect it once again.

Step 3

  1. 1
    Start the engine.
    Two circles: O (OK) and X (NG). Hand holding brake pedal down with depressed-pedal illustrations indicating pedal height should not change (OK) versus changing (NG).
    05U0PX-023
  2. 2
    Depress the pedal with the usual force.
  3. 3
    Stop the engine with the pedal depressed.
  4. 4
    Hold the pedal down for about 30 seconds.
  5. 5
    If the pedal height does not change, the unit is operating.
  6. 6
    If there is a problem, check for damage or improper connection of the check valve or vacuum hose. Repair if necessary, and check once again.
If the nature of the problem is still not clear after following the 3 steps above, follow the more detailed check described in "Method using tester," below.

(Method using tester)

Connect a pressure gauge, vacuum gauge, and pedal depression force gauge as shown in the figure. After bleeding the air from the pressure gauge, conduct the test as described in the 3 steps below.

a) Checking for vacuum loss

Unloaded condition

Checking for vacuum loss — Unloaded condition

  1. 1
    Start the engine.
    Two gauges: a stopwatch/timer showing seconds (left) and a vacuum gauge in mmHg with markings 100—740 (right) for checking vacuum loss.
    05U0PX-024
  2. 2
    Stop the engine when the vacuum gauge indicates 500 mmHg (19.7 inHg).
  3. 3
    Observe the vacuum gauge for 15 seconds. If the gauge indicates 475—500 mmHg (18.7—19.7 inHg), the unit is operating.
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