Strange noise when braking

[BCB00GT]

Hope I can describe the noise and when it happens for someone to shed some light. The noise I hear is ONLY when the brake pedal is applied and the car is moving (you can hear it good doing a low speed <20 mph stop). If I release the pedal while the car is moving, the noise stops. Hit the pedal again, the noise is again there. Once the car is stopped, with the pedal depressed, no noise.

The noise is not the pads/rotors, etc (non-metal). It sounds to be under the hood, a rotating or pumping/valve type noise (aka, hydraulic). A similar noise is heard when the car is stopped and the wheel is turned to the right. Align the wheel to center, no pressure, and the noise stops.

My assumption is power steering pump (cavitation?) or hydro-boost system.

Any thoughts. Thanks.

 

[Dragstr05]

Going by your post, and in what condition it happens, it would seem to me that it is deff Hydroboost, but I cannot be sure. Both conditions you have mentioned would be while the power steering pump may be/is under load.

Hopefully someone will chime in with better info. I love my stang, but work on toyota's.

 

[BCB00GT]

I would agree that the problem seems to be when the pump is under load. Not sure how the hydro-boost works. Could the pump be dead-headed? How does the hydro-boost work? Are solenoid valves involved?

 

[BlownFiveLiter]

Are the anti-rattle clips installed on the pads? The hydroboost system is pressurized at all times by the power steering pump.

 

[BCB00GT]

The anti-rattle clips are on. It is nothing with the brakes at the wheels. Definitely a power steering / hydro boost issue. How does the hydro boost work?

 

[Mike97gt]

This is a hydroboost issue.. check your P/S fluid level first and after using the brakes a few times and turning the wheel side to side check to see if there is air bubbles in the P/S fluid..

It sounds to me like you have either a leak somewhere in the P/S or hydroboost system or a bad P/S pump..

the way the hydroboost system works is it uses presure from the P/S pump to provide assist for the brakes. there is also a accumulator to provide a few assisted stops if there is a issue with the P/S pump or supply line.

 

[BCB00GT]

Is there any valves/solenoids between the power steering pump and the brake system. Exactly how is power steering fluid pressure used to pressure the hydraulic brake system since the fluids are different. Basically, what are the hydraulic details? Thanks.

 

[BCB00GT]

Follow up. The pump made noise (slight) when turning right, no noise to the left. I replaced the steering rack and all is good. There is a diverter in the rack that swings the fluid left or right. My guess is this or the piston in the rack was bad.

Took the gamble on the rack since I was sure my inner rods were bad also.