Power brake booster

Hi,

First, there will be a vacuum hose running between the intake manifold and the vacuum brake booster. Check to see if there are any cracks in the hose or if you can locate a leak.

If none are found, take a vacuum tester and confirm the booster can hold pressure. If it doesn't, the booster will need to be replaced.

Here is a link that explains how to replace the hose to the booster. If you find a leak, hopefully, this will help. The attached pics correlate with the directions.

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1998 Nissan-Datsun Sentra L4-1597cc 1.6L DOHC MFI (GA16DE)
Vacuum Hose Replacement
Vehicle Brakes and Traction Control Power Brake Assist Vacuum Brake Booster Service and Repair Procedures Vacuum Hose Replacement
VACUUM HOSE REPLACEMENT
REPLACEMENT

CAUTION: When installing vacuum hoses, pay attention to the following points.
- Do not apply any oil or lubricants to vacuum hose and check valve.

Pic 1

- Insert vacuum tube into vacuum hose as shown.

Pic 2

- Install check valve, paying attention to its direction.

INSPECTION

Hoses And Connectors
- Check vacuum lines, connections and check valve for airtightness, improper attachment, chafing or deterioration.

Check Valve

pic 3

- Check vacuum with a vacuum pump.
- Connect to booster side: vacuum should exist.
- Connect to engine side: vacuum should not exist.

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If you find the booster is bad, here are the directions for replacement. The attached pics correlate with the directions.

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1998 Nissan-Datsun Sentra L4-1597cc 1.6L DOHC MFI (GA16DE)
Booster Replacement
Vehicle Brakes and Traction Control Power Brake Assist Vacuum Brake Booster Service and Repair Procedures Booster Replacement
BOOSTER REPLACEMENT
REMOVAL

pic 4

Refer to the illustration when servicing.

CAUTION:
- Be careful not to splash brake fluid on painted areas; it may cause paint damage. If brake fluid is splashed on painted areas, wash it away with water immediately.
- Be careful not to deform or bend brake tubes during removal of booster.

INSPECTION

Output Rod Length Check

Testing For Vacuum At Booster

pic 5

1. Apply vacuum of -66.7 kPa (-500 mmHg, -19.69 inHg) to brake booster with a hand vacuum pump.
2. Check output rod length.
Specified length:
Models M195, S205 and C205: 10.275 - 10.525 mm (0.4045 - 0.4144 inch)

INSTALLATION

CAUTION:
- Be careful not to deform or bend brake tubes during installation of booster.
- Replace clevis pin if damaged.
- Refill with new brake fluid DOT 3.
- Never reuse drained brake fluid.
- Take care not to damage brake booster mounting bolt thread when installing. Due to the narrow angle of installation, the threads can be damaged by the dash panel.

Pic 6

1. Before fitting booster, temporarily adjust clevis to dimension shown. (Does not apply to models with ABS).
2. Fit booster, then secure mounting nuts (brake pedal bracket to brake booster) lightly.
3. Connect brake pedal and booster input rod with clevis pin.
4. Secure mounting nuts to 13 - 16 Nm (9 - 12 ft. Lbs.)
5. Install master cylinder.
6. Adjust brake pedal height.
7. Bleed air. Refer to Brake Bleeding Procedure.

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Let me know if this helps or if you have other questions.

Take care,

Joe