Guys - I am a Z06 owner, but my question relates to my Sequoia SUV. I have tried to no avail on the forum for toyotas - guess the guys there aren't technically oriented. At any rate- I believe my question could also relate to Corvettes.

Here goes -

2002 Sequoia SUV ; 118K miles.

Once the vehicle is warmed up - there is a "whooshing" or "whistling" noise upon releasing the brake pedal. The noise is inside the cabin- almost as if it is coming from where the pedal goes into the firewall. It's noticeable enough for everyone in the vehicle to notice. This has been going on for about a year- getting more pronounced.

Just recently replaced front rotors and all pads:brake fluid flushed. This did not alleviate the noise.

Note : Brake pedal effort is normal and brakes work good. No leakage from the brake master cylinder.

If not for the normal brake pedal effort- I would say my brake booster is going bad. This would not be a big deal except the part is ONLY available for my model thru the dealership at over $900USD . Also - my impression is brake pedal effort is overly firm when the Brake Booster fails- contrary to what I am experiencing which is normal pedal effort.

Again- not my Corvette, but the symptoms could be any car with power brakes I think.

Anyone have insight as to what is going on with this whistling brake pedal noise?

Thanks- again the forum for my SUV is hopelessly useless for anything but cosmetic advice. Pretty sure I can get better feedback from real car people here.

 

If you had a handheld vacuum pump, you could put vacuum on the booster and see if it held vacuum.

 

You might have a small pin hole in the seal where the actuator rods goes in, allowing air to enter and escape making a whistle or whoose...

 

Hi There;
To ops check your brake booster do the following.Pump the brakes several times until all the pressure is released( you hear the noise stop after a few pumps). Put your foot on the brake pedal & keep a steady pressure on it, then start the engine. If the pedal moves towards the floor then your booster is leaking internally. If the pedal does not move or moves slightly toward you your brake booster is fine.
Tstar's info. is also a very good possibility.
robsc501

 

Good info from above. If you do suspect the booster before you fork out the money for a new booster, replace the check valve that usually is pressed into the booster and then the large vacum line connects to it. It is usually a one way valve (not sure about the Sequoia but most cars seem to have one) and will probably only be around a couple of bucks. Replace the grommet it pushes into as well.

They even have some in the Help Motormite section of your local auto parts store and you can replace it yourself. Worst case is it has to come from a dealer but still likely under $25. I have seen more of these go bad on a host of different model cars as opposed to the actual booster.

Hope its is something inexpensive and simple like this...

Good luck.

 

If this is the case- does it mean the booster itself is good and just deal with the annoyance ?
As I mentioned I am getting plenty of power boost assist. I would imagine if my brake booster was leaking vacuum it would be very hard to pump the brakes to stop.

Thanks all for responding !! I will follow all suggestions and post my findings.

I also thought about the relief check valve- it's about $35 at the Toyo dealer but a heck of a lot less than the booster. However- still thrown off by my notion that leaking booster vacuum would be indicated by much harder brake pedal effort (right?). My pedal effort is normal- and the noise is in the cabin at the pedal ( seemingly).

 

Hi There NatB;
You sir are correct. You would have to use a strong brake pedal to stop your car. So the problem is elsewhere. Pull off the booster line with the engine running & you should feel strong suction by putting your hand over the hole.If thats the case the one way check valve is working satisfactory.Next look inside around the pedal area.
Sounds like Tstar is correct.
robsc501

 

NatB,
I am also a Sequoia and Vette owner. This forum rocks. I never get any response from the Toyota forum either, and I wasn't that impressed with the Mitsubishi forum for my sons Eclipse. It must be a Corvette thing. Looks like this forum has helped out once again.........Dave

 

Hey Nat,

Something I found on the Bendix brake web site relating to power boosters. Thought it might help the diagnosis. I know you said pedal was normal but just another step in figuring out the problem.

How do I determine if a hard pedal complaint is power booster-related or a foundation brake problem?
The easiest method is to deplete air from the vacuum booster by pumping the pedal until it's hard. Next, with the engine off, hold foot firmly on the brake pedal and start the engine. The pedal should drop slightly with engine vacuum and become firm if power booster is operating correctly. If hard pedal condition still exists check for binding linkage or over adjusted drum/shoe assemblies.


Mike

 

Thanks Mike ! OK- did as suggested, with engine OFF I pumped brake pedal until firm (2-3 strokes). Then with foot continuing to push down on brake pedal- I started the engine. With engine vacuum the brake pedal obtained assist and smoothly depressed.

So - perhaps not the brake booster after all ? This would be real good as Toyota built a very sophisticated brake booster which cost nearly $1,000USD and not available outside the dealerships for the 2002 model.

If not the brake booster- should I still be worried? Or just write it off as an annoying "whishing" sound and turn up the radio? Gotta think it's the "hole in a seal " theory previously posted by robsc501.

Been living with it for about a year- without impact to brake performance.

Hats off to Corvette Forum members !! I knew I would get some practical and knowledgeable advice .

 

Nat,

Well, if the brakes have still worked fine after over a year, I doubt that it is going to be a problem....However; if you are like me, the noise would be an issue. I'll spend all day to find a squeak and eliminate it.

I'd get under the dash and see if you can pinpoint the source exactly. Maybe its just the brake rod sliding in the seal of the booster and is something you can lubricate to make it go away? Not sure...just brainstorming.

Or could it be something on the stop light or cruise control actuator? Most are electric switches but I have seen some older cars where the cruise control mechanism that shuts it off when you touch the brakes was a small diaphragm. I doubt an 02 model would be like that but it can't hurt to look up under the dash and see.