Brakes make whosh sound when pressed

MARPINCAN

MEMBER
2008 PONTIAC MONTANA
3.9L
6 CYL
2WD
AUTOMATIC
120 MILES

Had hard brake pedal. After master cylinder was replaced this fixed the problem. While I was trouble shooting the hard brake problem, I noticed that depressing the brake pedal would result in a whooshing air sound coming from the pedal area. After the master cylinder was replaced, the whooshing sound was still there. You can only hear it when pressing the pedal hard/fast and when you stop pressing the pedal it stops and the pedal holds. I am trying to figure out if this is of concern or not. I have read that it could be and I have also read that it is not. The brakes seem to work fine but my other vehicles do not make this sound. Is this a problem or not?

1 Reply

ASEMASTER6371

MECHANIC
52,797 POSTS

Good evening,

The booster has a vacuum leak and it is leaking out the shaft at the pedal.

I would replace the booster assembly.

Roy

Procedure

Power Vacuum Brake Booster Replacement

Removal Procedure
Caution: Refer to Brake Fluid Irritant Caution (See: Brakes and Traction Control > Technician Safety Information > Brake Fluid Irritant Caution).

Notice: Refer to Brake Fluid Effects on Paint and Electrical Components Notice (See: Brakes and Traction Control > Vehicle Damage Warnings > Brake Fluid Effects on Paint and Electrical Components Notice).

1. Relieve fuel line pressure. Refer to Fuel Pressure Relief (With CH 48027) (See: Fuel Pressure Release > Procedures > Fuel Pressure Relief (With CH 48027))Fuel Pressure Relief (Without CH 48027) (See: Fuel Pressure Release > Procedures > Fuel Pressure Relief (Without CH 48027)).
2. Drain the cooling system. Refer to Cooling System Draining and Filling (Static Fill LZ9) (See: Cooling System > Removal and Replacement)Cooling System Draining and Filling (Vac-N-Fill) (See: Cooling System > Removal and Replacement).
3. Remove the coolant recovery reservoir. Refer to Coolant Recovery Reservoir Replacement (See: Coolant Reservoir > Removal and Replacement).
4. Remove the left front cross brace. Refer to Front End Sheet Metal Diagonal Brace Replacement (Pontiac) (See: Structural Brace > Removal and Replacement)Front End Sheet Metal Diagonal Brace Replacement (Chevrolet) (See: Structural Brace > Removal and Replacement).
5. Remove the engine control module (ECM) cover from the air cleaner housing.
6. Remove the ECM and set aside. It is not necessary to disconnect the electrical connector. Refer to Engine Control Module Replacement (See: Engine Control Module > Removal and Replacement).
7. Remove the air cleaner assembly. Refer to Air Cleaner Assembly Replacement (See: Air Cleaner Housing > Removal and Replacement > Air Cleaner Assembly Replacement).
8. Remove the fuel lines from the pipes and vapor line. Refer to Metal Collar Quick Connect Fitting Service (See: Fuel Line Coupler > Removal and Replacement > Metal Collar Quick Connect Fitting Service) orPlastic Collar Quick Connect Fitting Service (See: Fuel Line Coupler > Removal and Replacement > Plastic Collar Quick Connect Fitting Service).
9. Remove the heater hose from the coolant cross over pipe and reposition out of the way. Refer to Heater Inlet Hose/Pipe and Heater Outlet Hose/Pipe Replacement (See: Heater Hose > Removal and Replacement > Heater Inlet Hose/Pipe and Heater Outlet Hose/Pipe Replacement).
10. Release the fuel lines from the shock tower for easier access to the brake pipes.
11. Disconnect the fluid level sensor switch from the brake master cylinder.
12. Disconnect the brake lines from the master cylinder and remove the master cylinder. Refer to Master Cylinder Replacement (See: Brake Master Cylinder > Removal and Replacement > Master Cylinder Replacement).
13. Remove the brake pressure modulator valve (BPMV) assembly and bracket. Refer to Brake Pressure Modulator Valve Replacement (See: Hydraulic Control Assembly - Antilock Brakes > Removal and Replacement).

Images (Click to make bigger)