Intro & Hissing when releasing brake pedal

[sbarber]

So I've been visitor for a while and now I need some help. First a little about me and my truck.

About me:
Software engineer, working mainly on web based insurance software.
Married
2.5 kids (due in January)
1 dog (English Springer Spaniel)
Would rather try it myself first before paying someone else to do it.

About the truck:
2002 Sequoia Limited 2wd
~138k miles
bought used in 2005 with 99k miles on it.
w/o brake TSB
slotted / drilled rotors (on order)
timing belt / water pump replaced @ 100k


My Problem:
We've been experiencing a hissing noise when we release the brake pedal. The hissing can be stopped by reapplying the brakes or lightly tapping the brake pedal (kind of like hitting the side of you tv for a better picture. )

I'm guessing it is the brake booster only because it sounded good. Does anyone have any suggestion about how I can determine this for sure? Since it seems like an air leak of some type, is there a seal I can replace myself without having to get a whole new brake booster?

- Scott

[mustang67408]

Yes, your right it is the brake booster.(common problem here in LV). There is nothing else attached to the brake pedal that could HISSSS. That is the engine vacuum leaking out of the booster.
No, they are not servicable. There are a few sensors inside them. 1:Brake force switch 2: ACTIVE Booster Solenoid.
Yes you can replace it yourself. You dont even have to break loose the master cylinder lines, or bleed the brakes when your done.

[sbarber]

Thanks for the reply. It looks like I will tackle the job myself if I can find a replacement booster. I've checked around at the local parts stores and no one can seem to find one. Haven't had much luck with websites either.

If anyone has a recommendation on where I might find one I'd be very interested. (And Toyota @ $900 is out of the question..... at the moment anyway)

One more question: Can I substitute a brake booster from the 2002 Tundra? I found this on the autopartswarehouse.com site
Part Number: A1534902
MFR#: 534902


- sb

[sbarber]

It may all be a moot point, but I tried troubleshooting some more own my own, in the dark, with a shop light Short story it didn't work. I tried screwing the U-bolt (attached to the powerbooster) down a little bit more thinking that the brake pedal might pull back a little harder and complete the seal. No dice.

In my test drive I did notice that the hissing really starts after the engine has warmed up. Not sure why affects anything, but apparently it does. After I told my wife she said "Oh, yeah I knew that" Doh!!!

Again still looking for the cheaper alternative. I started playing with the pedal some more and how it is recoils when letting off the brake. Any chance the spring is worn and new spring would fix the problem?

- sb

[mustang67408]

Anything is possible, but in no uncertain terms the brake booster should not leak at all.

It is a fairley common problem we see every month, but Toyota has NO TSB or any field fix. The only thing we can do is replace them with new units. What would a customer say if I told them I replaced the return spring for vacuum leak. Boosters just shouldnt leak.

I understand $$$ is alot of money, I have a 04 Sequoia and know someday this may happen to me, so I feel your pain.

You might try a stiffer return spring , but when you apply the brake pedal, it will probably leak as you push the pedal down, which in turn will lean out the engine (vacuum leak). The warmer it gets , the worse it gets, is probably because when the engine gets warmer it creates more vacuum, piston rings seat better and everything swells and fits together better.

Let us know if you fix it. I am all ears

[sbarber]

Hey guys, I'm a little stuck at the moment. I was able to get a used brake booster sent which I thought was going to fit. However, upon closer inspection there is an additional 3-pin connector.

Does anyone know what this connector is for? Can I use the booster without it?

I have posted some pics in my album of the new and old booster. I tried to call the local toyota parts guy and we couldn't get in sync with part numbers.

Any information would be helpful.

Pics: Tundra Solutions Forum - sbarber's Album: 2002 Brake Booster Swap

Thanks,

- Scott

[mustang67408]

That booster is for a 05 and newer Sequoia. The extra plug is for the Pedal Stroke Sensor that is not used on your 02. It should work, the other plug that matches yours is wired exactly the same as yours. It should work just fine, as long as the first plug, plugs in.

[sbarber]

Awesome. Thanks for the quick response. Looks like I have plans for tomorrow afternoon.

- sb

[sbarber]

Just to complete the thread. I installed the new power brake booster in about 1.5hrs. It was pretty straight forward and as suggested I didn't have to disconnect the brake lines. I used the newer booster and have just left the "extra" 3 pin connector disconnected.

I'm happy to report that the brakes are now much improved and the "hissing" is gone, it even passed the "wife test".

Thanks mustang67408 for your reassurance and assistance.

So a new brake booster (junk yard search), Centric slotted / drilled rotors (from Wheeler's), w/ceramic pads (from Wheeler's) for ~$450, 2 weekends and ~4 hrs.

Hmmmm, I wonder what else is broken..........

-sb

[mustang67408]

Glad everything worked out. I do Love our 04 sequoia too.