Join Date: Oct 2003
Bronco Info: 96 Bronco XL 5.0 E4OD, Man Xfer/Hubs
Agree with Big Blue.
You have good vacuum and fit in the range according to Brake, Power, Hydro-Boost Booster, by Ford in a 96
Disconnect vacuum booster hose from booster.
Connect Rotunda Vacuum/Pressure Tester 164-R0253 or Rotunda Vacuum Tester 014-R1054 or equivalent to the vacuum hose with a T-fitting.
Key on, engine running. Allow engine to reach normal operating temperature.
Record the vacuum pressure.
Is the vacuum reading 57-70 kPa (17-21 in-Hg)?
Yes GO to N2.
No TUNE UP or REPAIR engine as required.
N2 SYSTEM INSPECTION
Reconnect the vacuum line.
Inspect power brake booster check valve, rubber grommet and all vacuum plumbing for cracks, holes, bad connections or missing clamps.
Push down on brake pedal and hold.
Key on, engine running.
Does the brake pedal move downward when the engine is started?
Yes Vacuum system is OK.
No GO to N3 for diesel engines. GO to N4 for gas engines.
N4 COMPONENT ISOLATION CHECK
Reconnect the vacuum gauge to the same point as in Step N1, but leave the rest of the system connected.
Key on, engine running at idle until vacuum reaches 57-70 kPa (17-21 in-Hg).
Observe vacuum gauge for 1 minute.
Does vacuum pressure drop more than 1 in-Hg?
Yes DISCONNECT each component one at a time and REPEAT the test procedures in N4 until the leaking component is found. PLUG the disconnected vacuum line while performing the test procedures. REPAIR or REPLACE as required. On diesel engines with dash-mounted power brake booster, REPLACE power brake booster check valve also.
No GO to N5.
N5 BOOSTER LEAK CHECK
Run engine until vacuum pressure reaches 57-70 kPa (17-21 in-Hg).
Push down on the brake pedal and hold for a few seconds and release.
Does the vacuum drop to 0 kPa (0 in-Hg)?
Yes REPLACE power brake booster. No System checks OK. REMOVE vacuum gauge and RECONNECT all vacuum lines.
"...Use "Hard (Heavy Duty)" vacuum line for booster. Regular rubber hose such as used for WS washer fluid line will likely collapse after about say, 20 years. Inspect for any sign of kinking or collapse. Check vacuum draw available with a gauge connected between engine and booster. At idle, healthy engines draw somewhere between 17 and 22 in Hg. Check vacuum by depressing brake pedal firmly until it stops. The gauge should read a drop to approximately 10 in. Hg and then quickly recover to a normal reading. If vacuum takes too long to recover, there is a restriction in the volume, i.e.: fitting clogged or vacuum hose collapsed. Repair as necessary. While a defective booster will cause a hard pedal, a spongy or low pedal requires a hydraulic system check..." by Cardone