3500 4x4 Pickup L6-359 5.9L DSL Turbo (1996)
Vacuum Brake Booster: Testing and Inspection
DIESEL ENGINE VACUUM PUMP OUTPUT
Diesel Vacuum And Power Steering Pump Assembly
Diesel Vacuum Switch Location (without ABS)
Vacuum pump diagnosis involves checking pump output with a vacuum gauge. The low vacuum warning switch can also be checked with a vacuum
gauge.
A standard vacuum gauge can be used to check pump output when necessary. Simply disconnect the pump supply hose and connect a vacuum gauge to
the outlet port for testing purposes. Vacuum should hold steady in a range of approximately 8.5 to 25 inches at various engine speeds.
A low booster vacuum condition or a faulty low vacuum warning switch will cause the brake warning lamp to illuminate. If the lamp does go on and
indicates the existence of a low vacuum condition, check the vacuum pump, booster and warning switch as follows:
1. Check vacuum pump oil feed line. Verify that line connections are secure and not leaking. If leakage is noted and pump is noisy, replace pump.
2. Disconnect supply hose to booster. Connect vacuum gauge to this hose and run engine at various throttle openings. Output should range from 8.5
to 25 inches vacuum. If vacuum is consistently below 8.5 inches, problem is with vacuum hoses or pump component. If output is within specified
limits, continue testing.
3. Check booster operation as described in diagnosis section. Replace check valve, vacuum hoses, or booster if necessary However, if booster
operation is correct but warning lamp is still on, continue testing.
4. Disconnect vacuum hose at warning switch. Plug hose and connect hand vacuum pump to switch.
5. Start and run engine.