How do I check if the brake booster is working?

Depress the brake pedal several times with the engine off and check there is no change in pedal stroke. Then depress the pedal and start the engine — if the pedal goes down slightly, operation is normal.

How do I test the brake booster for air tightness?

Start the engine, then stop it within one or two minutes and depress the pedal several times slowly; if the pedal goes further down the first time but gradually rises after the second or third, the booster is airtight. Alternatively, depress the pedal with the engine running, stop the engine with the pedal depressed, and hold for thirty seconds — no change in pedal stroke means the booster is airtight.

What are the torque specs for brake booster installation?

16-22 N·m (1.6-2.2 kg-m, 12-16 ft-lb) for one fastener group and 8-11 N·m (0.8-1.1 kg-m, 5.8-8.0 ft-lb) for the mounting nuts, per the removal and installation diagram.

When should the brake booster check valve be replaced?

When pressure is applied to the brake booster side of the check valve and the valve does not open, replace the check valve with a new one.

Does the brake booster output rod length need adjustment?

No. The manual states output rod length A does not require adjustment.

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Nissan Micra Brake Booster Check, Removal & Inspection - Service Manual BR-8

Brake booster operating, airtight and check-valve inspection procedure with removal torque specs

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Brake booster service page: operating check, airtight check (hold pedal 30 sec), check-valve directional test, and removal torques 16-22 N-m and 8-11 N-m. Output rod length needs no adjustment.

AI caption November 2005 · Photo 292 of 412

This is page BR-8 of a Nissan factory service manual covering the brake booster. It provides four procedures: an Operating Check (depress the pedal several times with the engine off to verify no change in stroke, then start the engine — the pedal should sink slightly if operation is normal); an Airtight Check (two methods using engine start/stop and pedal behavior over 30 seconds to confirm the booster holds vacuum); Removal and Installation (an exploded diagram of the booster, master cylinder, and pedal linkage with torque specifications of 16-22 N·m (1.6-2.2 kg-m, 12-16 ft-lb) and 8-11 N·m (0.8-1.1 kg-m, 5.8-8.0 ft-lb)); and Inspection procedures for hoses and connectors, the check valve, and output rod length. Inspection instructions include checking vacuum hoses and the check valve for air tightness, replacing the check valve if it does not open when pressure is applied from the brake booster side, and a caution not to apply oil or lubricants to the vacuum hose or check valve. The output rod length (dimension A) does not require adjustment. Illustration reference codes SBR773, SMA157A, SBR846, and SBR426 appear on the diagrams.

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Frequently asked questions

How do I check if the brake booster is working?: Depress the brake pedal several times with the engine off and check there is no change in pedal stroke. Then depress the pedal and start the engine — if the pedal goes down slightly, operation is normal.
How do I test the brake booster for air tightness?: Start the engine, then stop it within one or two minutes and depress the pedal several times slowly; if the pedal goes further down the first time but gradually rises after the second or third, the booster is airtight. Alternatively, depress the pedal with the engine running, stop the engine with the pedal depressed, and hold for thirty seconds — no change in pedal stroke means the booster is airtight.
What are the torque specs for brake booster installation?: 16-22 N·m (1.6-2.2 kg-m, 12-16 ft-lb) for one fastener group and 8-11 N·m (0.8-1.1 kg-m, 5.8-8.0 ft-lb) for the mounting nuts, per the removal and installation diagram.
When should the brake booster check valve be replaced?: When pressure is applied to the brake booster side of the check valve and the valve does not open, replace the check valve with a new one.
Does the brake booster output rod length need adjustment?: No. The manual states output rod length A does not require adjustment.