Weird noise coming from brake booster.

[Devin Wright]

When I turn my car off (kill the engine) or put it to the ON position and back to the OFF position. I hear this weird, rotating noise coming from the passenger side of my dash, and opening the hood it sounds like it is coming from the brake booster. I do have an ABS light on, but my brakes work perfectly fine. Could this be related? Or what is this? Is this something I need to be worried about?

 

[XLTrunner]

There's nothing inside a brake booster that can rotate and make noise. It's basically a tin can with a vacuum diaphragm. The ABS light being on is most likely a faulty wheel sensor.

Does you truck have EATC? Could the noise be the control actuator motor trying to engage the blend door? My Sable did this and I had to replace the motor ass'y.

 

[chefduane]

Typically a failing brake booster will make a hissing sound, indicative of a failing diaphragm XLT mentioned above. Also the pedal will be initially rock hard then slowly turn to mush as the brakes grab. The blend door on Gen II's is located underneath the glove compartment so I would think that that might be the first place to check.

 

[Devin Wright]

Typically a failing brake booster will make a hissing sound, indicative of a failing diaphragm XLT mentioned above. Also the pedal will be initially rock hard then slowly turn to mush as the brakes grab. The blend door on Gen II's is located underneath the glove compartment so I would think that that might be the first place to check.

The thing is, my brakes feel fine, they work really well actually. But, if I was to get to the blend door, what would I need to check for exactly?

 

[Devin Wright]

There's nothing inside a brake booster that can rotate and make noise. It's basically a tin can with a vacuum diaphragm. The ABS light being on is most likely a faulty wheel sensor.

Does you truck have EATC? Could the noise be the control actuator motor trying to engage the blend door? My Sable did this and I had to replace the motor ass'y.

Not sure if I am 100% correct here, but, I don't believe it does. I generally control climate controls manually. I just put it on AC and select a wind force and go with that. I do however, turn off the AC before I turn off the vehicle. But, it does this when I don't even turn the car on. If I put the car to the "on" position, and turn it back to the "off" position, it'll make the noise.

 

[koda2000]

The thing is, my brakes feel fine, they work really well actually. But, if I was to get to the blend door, what would I need to check for exactly?

Drop the glove box to get access to the blend door actuator, which is located on top of the heater plenum. Unplug the white electrical connector and see of the noise stops. Replacing the actuator is a PITA and replacing the blend door is an even bigger PITA, so make sure that it's the problem first.

 

[lobo411]

The easiest way to test the blend door system is to sweep the temperature control from hot to cold or vice versa, and listen for the noise. I think you can do this without starting the car but with the ignition switch in "run," so you can be sure the noise is coming from something electrical rather than mechanical.

 

[chefduane]

I can't add anything much more to what Koda said other than to affirm that it is a PITA to do. Search on 'blend door' and you will find a number of thread dealing with a fix. Also, once you confirm that it IS the blend door there are a kit style fixes that are available. And even through the motor may come on, that doesn't mean that the blend door is ok. The gear on the end of the motor shaft, or the gear on the door may be stripped.

 

[Turdle]

whoa! hold up a sec!

Don't you guys think he should be checking for a leaking check valve or brake booster before the blend door attack? he said whirring noise, but I thought the blend door motor does a clicky noise thing when it messes up.

Passenger side whirring noise. ( I am going to assume he has the "blower "mixed up with the "brake booster" which is on the driver side)

possibly the blower motor? Blower motor relay stuck "on" and running on low speed?

Could be a small leak in the vacuum system, when engine is turned off the reservoir is still pulling vacuum through it. I have seen vacuum lines leak and make some of the strangest sounds

 

[koda2000]

whoa! hold up a sec!

Don't you guys think he should be checking for a leaking check valve or brake booster before the blend door attack? he said whirring noise, but I thought the blend door motor does a clicky noise thing when it messes up.

Passenger side whirring noise. ( I am going to assume he has the "blower "mixed up with the "brake booster" which is on the driver side)

possibly the blower motor? Blower motor relay stuck "on" and running on low speed?

Could be a small leak in the vacuum system, when engine is turned off the reservoir is still pulling vacuum through it. I have seen vacuum lines leak and make some of the strangest sounds

Seems like a lot of "assuming". Maybe I guess, who knows?

 

[XLTrunner]

Yeah...but, he describes it as a "weird, rotating noise" not "whirring". I've never experienced a vacuum leak sounding like a rotating noise. Need more info, I guess.

 

[Turdle]

rotating noise and passenger side is what tells me blower motor. Just thinking out loud.
Brake booster is on the driver side. I admit some confusion on my part as always.

However. MY buddy once replaced an alternator for what sounded like a whirring bearing. new one and the noise was there. he brought it to my house and yes, only when engine was running, and it sounded like it was the alternator bearings. The sound even seemed to come from it.
It was a 93 350 vortech, the small elbow vacuum hose on the lower front of the throttle body had a hole with a "flapper" in it that for lack of better terms made a reed. This resulted in a whirring, bad bearing sound. In fact we were lucky to find it.

Just trying to help. I am pointing out things that are free to look at, you guys have him replacing a blend door already.

 

[XLTrunner]

I agree...simple things first. I wouldn't wish replacing/repairing a blend door on anyone...lol! It just brought to mind a weird rotating noise I had when the actuator motor had a stripped gear on my Sable. Fortunately, I got away with only having to replace it...and, not having to mess with the blend door.

People tend to describe sounds in different ways.

 

[Devin Wright]

Lobo411, my heat does not work, I need my heater core replaced. Last time I tried turning on my heat out of curiosity. It almost sounded like me engine revved, but, the engine RPM's didn't change and I didn't feel any air force (if you wanna call it that) coming from the vents. It was soooo freakin' weird, so I've never touched the heater controls after that. But, the AC works fine.

XLTrunner, it's a rotating noise, not a whirring noise.


To everyone: I gave all the info I could. I literally hear a rotating noise from my passenger side, and when I open the hood, it sounds like it's coming from the brake booster. But, the brakes work perfectly fine. They don't feel mushy or hard to press. They feel like normal brakes. When the brake booster went out on my dads truck, the brakes felt like you had to all but press them to the floor. It went out on me when I was towing a trailer home, and boy that scared the living sh*t out of me. I was about to pull into my driveway and the brakes didn't work and I panicked and slammed the E-brake going like maybe 5 MPH so I didn't hit our garage door. But, this feels nothing like that. The brakes feel the exact same as they always have.

 

[Turdle]

See, now here is where I am getting confused. You say sound from passenger side, and from the booster, but booster is on driver side. The blower motor is on the passenger side. It makes a rotating sound, and your heater not working? Put it together and--

Are you absolutely positive you are not referring to the blower motor making noise? Upload a picture of what is making noise please.

 

[chefduane]

I think Turdle is on to something. The only thing that could make a rotational sound on the left side of the engine bay (assuming the blend door has been ruled out) is the squirrel cage fan of the blower. And, the blower housing >might could< be confused with a brake booster. In the old days (!) wasn't the brake booster a big round contraption with the master cylinder mounted to it?
Could look kinda' like a fan housing. Even if the motor is still working fine there could be debris stuck in the housing that might make a sound against the blades as the fan spins. The fan housing is easy enough to pull with no special tools. The relay might also be something to check.

 

[Turdle]

leaves and debris can work down into the blower housing also. So look for this when you are in there. The blower resistor does get hot, and, can ignite that stuff.

 

[ThreeJs]

Do you have a working or broken power antenna? It's located on the passenger side.
Turning the key on/off, the power motor for my antenna makes a whirring sound because my antenna only goes up/down halfway.