Crown Victoria V8-281 4.6L SFI (1998)
Vacuum Brake Booster: Adjustments
The vacuum power brake booster on non-ABS vehicles has an adjustable push rod (output rod) which is used to compensate for dimensional
variations in an assembled power brake booster. The push rod length is adjusted after each power brake booster has been assembled in production. A
properly adjusted push rod that remains assembled to the power brake booster with which it was matched in production should never require a service
adjustment.
A power brake booster that is suspected of having an improper push rod length will indicate one of the following:
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A push rod that is too long will prevent the brake master cylinder piston from completely releasing hydraulic pressure, causing the brakes to drag.
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A push rod that is too short will increase brake pedal travel and cause a groaning noise from the power brake booster.
If necessary, booster push rod length can be verified with a push rod gauge by using the following procedure:
1. Without disconnecting the brake tubes, disconnect the brake master cylinder, and move it away from the power brake booster.
CAUTION: The brake master cylinder must be supported to prevent damaging the brake tubes.
2. With the engine running, gauge and adjust the push rod length from the knurled area. A force of approximately 22 N (5 lbs.) applied to the push
rod with the gauge will make sure that the push rod is seated within the power brake booster.
CAUTION: Do not adjust push rod length too long or brake drag could result.
3. Install the brake master cylinder on the power brake booster. Gradually alternate tightening the retaining nuts to 21 - 29 Nm (16 - 21 ft. lbs.).
