Almost like the sound of a whale until I release pressure from the brakes

Hi,

replacing the vacuum brake booster really isn't too hard. It takes a little time, but as long as the directions are followed, you should be fine. You will need to remove the brake master cylinder and disconnect the brake pedal from the booster push-rod.

Here are the directions specific to your vehicle for replacement. The pics below correlate with the directions.

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2007 Nissan-Datsun Sentra L4-2.5L (QR25DE)
Brake Booster
Vehicle Brakes and Traction Control Power Brake Assist Vacuum Brake Booster Service and Repair Removal and Replacement Brake Booster
BRAKE BOOSTER
BRAKE BOOSTER

Removal and Installation

Exploded View BR-7

pic 1

Exploded View BR-19

pic 2

REMOVAL

CAUTION:
Be careful not to splash brake fluid on painted areas such as body. It may cause paint damage. If brake fluid is splashed on painted surfaces of body, wipe them with cloth immediately and then wash it away with water.
Be careful not to deform or bend brake tubes while removing and installing brake booster.
Replace clevis pin if it is damaged.
Be careful not to damage brake booster stud bolt threads. If brake booster is tilted or inclined during installation, dash panel may damage the threads.

1. Remove vacuum hose from brake booster.
2. Remove master cylinder assembly.

Pic 3

3. Remove snap pin and clevis pin on the clevis of the brake booster, and remove input rod from brake pedal.
4. Remove brake pedal nuts on pedal bracket.
5. Remove between spacer and dash panel nut from dash panel.
6. Remove brake booster and spacer from vehicle.
7. Remove spacer from brake booster.

INSTALLATION

pic 4

1. Loosen lock nut to adjust input rod length so that the length B satisfies the specified value.
Length "B": 163.2 - 164.2 mm (6.43 - 6.46 in)
2. Install spacer to brake booster and tighten spacer nut (brake booster side) to the specified torque.
3. After adjusting length "B", temporarily tighten lock nut to install brake booster assembly to dash panel. At this time, make sure to install a gasket between brake booster and vehicle.

CAUTION: Be sure to install the gasket between brake booster and vehicle.

4. Connect brake pedal to clevis of input rod with the clevis pin and snap pin.
5. Install brake pedal bracket nuts and tighten them to the specified torque.
6. Adjust the height and play of brake pedal.
7. Tighten lock nut of input rod to the specified torque. Refer to Exploded View BR-7.
8. Install vacuum hose into brake booster.
9. Bleed air from brake system.

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I hope this helps. Let me know if you have other questions.

Take care and God Bless,

Joe