Question about 2004 Pontiac Aztek

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Applying brakes I hear a hissing sound - 2004 Pontiac Aztek

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Hissing could mean a few different things but depending on how many miles you have on e the car and or how many sets of brake pads have been changed since 2004, I would say your early warning indicators are telling you take your brake pads are about done and if you don't get it to the shop or whatever you're going to do, you'll soon start to have metal on metal and you'll need to buy new rotors when that happens. To give you and idea...4 rotors and pads will probably run you around $800+ at the dealer.

Posted on Jan 16, 2013

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  • Rishiraj Sookhdeo Jan 16, 2013

    I have changed the brake pads about 6 months ago. Also when I come to a stop and step on the brake I hear the hissing sound and the car stalls out, so I have to put it in neutral and then slip it in drive. Sometimes even at neutral it cuts off.

  • xkikbxr Jan 18, 2013

    Open the hood of the car. On the driverside closest to the windshield you'll see a big round object with a hose coming out of it and your master brake cyliner is attached to it. Have someone sit in the car behind the wheel.While the car is running put it in gear and see if the hissing is coming from that area. It seems like it could be losing vacuum. So check the hose real good for leaks, caracks, holes..ect. Check the plastic fitting that is between the hose and the brake booster. If the hissing is coming from the brake booster itsel it is probably a bad bladder inside the booster.f

  • xkikbxr Jan 18, 2013

    I should have said, put the car in gear while the brake is being held down.



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What kind of clicking noise do you expect to hear? Applying the main brakes is usually a silent activity.
If you are referring to the emergency brake, it is the clicking of the ratchet when applying the emergency brake. The clicking is the sound of spring loaded metal teeth bouncing along a cog wheel. The action is similar to the teeth on a hand winch that does not allow backward turning. If when applying the emergency brake the sound is not heard then the spring may be broken or dislodged.
Does the brake engage? Does the handle stay pulled until the brake is released? If not then the locking of the brake is not happening.

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Its a constent hissing from my brakes in my Mazda 2001 tribute. The noise does stop When i press on the brakes but as soon as i let off them the hissing continues. Ive read it could be the brake booster. ...

It is the booster, but it might not be abnormal.

Vacuum from the engine is supplied to the booster, and vented if the brakes are not being applied.

When you step on the pedal, the movement of the pedal blocks the vents, allowing the vacuum to build up. That vacuum then pulls on a diaphragm, assisting you in applying the brakes.

Most people can’t hear that venting, some can.

You should, of course, have it checked out, but it sounds as if this might be normal operation.

The booster is bolted to the firewall, and then the brake master cylinder is bolted to the forward side of the booster.

To replace it you disconnect the brake pedal, remove the master cylinder, take the vacuum line off the booster, unbolt it from the firewall.

Install the new booster by reversing these steps.

But I don't think you need one, from what you say.

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When u press on the brakes on my expedition, i hear air escaping.

If it is a constant hiss with your foot on the pedal, you have a bad brake booster. If you hear a hiss, and nothing else while holding the pedal, it is the air escaping from the booster boot, and should not pose a problem.

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