Hising Sound

[dreammerchants]

I have recently noted a hissing sound thats coming from my 2004 4runner SR5 Sport. The sound disappears when I step on the brakes but reappears when I take my foot of the break pedal.

Any one have any tips on whats causing the problem. No lights are coming up on the dashboard console during this time.

Cheers

 

[RoarFunner]

Sounds like it could be a leak in the vacuum booster or a vacuum line...or even the check valve. Has the brake pedal been harder lately? Any rough idling at all?

 

[Methodical]

Our trucks don't use vacuum assist. That makes it even odder!

Turn off your car, then put turn in the accessory position (not RUN, and not start).

Press your brake pedal hard, and let it come back. Keep cycling until the warning lights and alarm tone come on. Post back with the number of pumps it takes.

 

[Falls]

Do you have rear self leveling suspension ?

 

[RoarFunner]

Our trucks don't use vacuum assist. That makes it even odder!

I knew my 08 didn't. Wasn't sure if the 03 still used vac boost or not. Very weird.