Inspection Using Simplified Tester

WARNING: This page is about a different car, the 2017 Mitsubishi Mirage. However, it is still accessible from the selected car via links, so may be relevant.

Before starting this inspection, remove the brake booster check valve from the vehicle and check its operation (Refer to MASTER CYLINDER ASSEMBLY AND BRAKE BOOSTER ASSEMBLY ).
Connect a vacuum gauge between the vacuum hose (incorporating the check valve) and the brake booster.

Connect a pressure gauge and a pedal depression force gauge as shown. Air-bleed the pressure gauge and then follow the procedure below:

Airtightness test with no load
Start the engine, and stop it when the vacuum gauge indicator has reached approximately -67 kPa (-148 lb). The result is judged as "Good" when the drop of the vacuum approximately 15 seconds after the engine was stopped is within -3.3 kPa (-7 lb).
Airtightness test with load
Start the engine and depress the brake pedal with 200 N. Stop the engine when the vacuum gauge indicator reached approximately -67 kPa (-148 lb). The result is judged as "Good" when the drop of the vacuum approximately 15 seconds after the engine was stopped is within -3.3 kPa (-7 lb).

When one or more of the above check results are judged as "No Good," the vacuum hose or brake booster is suspected faulty.

Fig 1: Vacuum Gauge Connected To Vacuum Hose (Incorporating Check Valve) And Brake Booster
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

Brake booster characteristics test

Perform this test after the above (1) and (2) were performed.

Non-servo effect test

With the engine stopped, make sure that the vacuum gauge reading is 0 kPa (0 lb). Depress the brake pedal with 100 N (22.5 lb) and 300 N (67.4 lb), and measure the fluid pressure generated.

Standard value:

Item	Pedal depression force
Item	100 N (22.5 lb)	300 N (67.4 lb)
Generated fluid pressure kPa (psi)	0 - 516 (0.0 - 74.8)	2, 080 - 2, 780 (301.7 - 403.2)

Servo effect test
Start the engine. Depress the brake pedal with 100 N and 300 N when the vacuum gauge indicator reached approximately -67 kPa, and measure the fluid pressure generated.

Standard value:

Item	Pedal depression force
Item	100 N (22.5 lb)	300 N (67.4 lb)
Generated fluid pressure kPa (psi)	4, 380 - 5, 780 (635.2 - 838.3)	9, 020 - 10, 420 (1, 308.2 - 1, 511.2)