hissing under dash

[bronzemaxell]

my 1999 solara V6SE has developed a hissing noise under dash recently, the hissing only happen with engine running, but as soon as i tap on the brake lightly, the hissing stopped, and as soon as I take my foot off the brake pedal, the hissing returns, apply brake, no hissing, the hissing noise sound very similar to A/C compressor running, or power steering, but i know AC or power steering were not running at the time.

i can only hear the hissing in my driver seat when engine running, i tried to pop the hood and listen near the brake booster area, but seems like the engine running noise shadow the hissing noise that i heard in my driver seat.
what is failing?
brake booster diaphram? push rod seal???

[pmesfun]

I'm probably wrong but maybe a crack in vacuum lines, mainly brake booster hose.
BTW how many camry/solaras do you have, haha?

[sikwitit]

you have a snake under your dash lol
i would check all your brake/vaccum hoses for damage and replace them
sean

[bronzemaxell]

the brake pedal doesn't feel soft, spongie, or extremely hard, it has a very good brake feel, and very good stopping distance,
i did tried with engine off, step on brake pedal once, the pedal goes down like it would, then release, and step on it 2nd time, the brake pedal feel hard, did it again 3rd time, and still feel hard, and if i keep holding it, it doesn't sink any further.

with engine off, and after stepping the brake pedal a few times, and still holding the brake pedal, i start the engine, and brake pedal goes down further a bit, but not really all the way to floor.


i only have 5 camry (gen3, gen4, gen 5) and 1 rx300

[Gothmog3VZ]

Originally Posted by bronzemaxell

i only have 5 camry (gen3, gen4, gen 5) and 1 rx300

"Only" 5 Camries wish I could say the same

and could just be a leak in the vacum lines, connected to the booster. that's my thought though...

[73sport]

Let it idle for a minute and turn it off. Stick you head under the dash. You hear the hiss right.

Now do the same but from the engine side. You may get lucky and hear the hiss which because it changes with the pedal press could be the seal behind the brake master cylinder.

Use a paper towel tube up to your ear to isolate where the sound is coming from. If at the base of the master cyl, pull the mc clean the shaft, lube it with appropriate lube, and or replace the seal if the edges around the pushrod are damaged. A rusted shaft will destroy the seal fast. Polish it with 2000 grit emry cloth.

Worst case is the hiss is under the dash and you end up replacing the MC. Use the tube under the dash too as it could be soemthing other than the MC but I doubt it.

[bronzemaxell]

Originally Posted by 73sport

Let it idle for a minute and turn it off. Stick you head under the dash. You hear the hiss right.

Now do the same but from the engine side. You may get lucky and hear the hiss which because it changes with the pedal press could be the seal behind the brake master cylinder.

Use a paper towel tube up to your ear to isolate where the sound is coming from. If at the base of the master cyl, pull the mc clean the shaft, lube it with appropriate lube, and or replace the seal if the edges around the pushrod are damaged. A rusted shaft will destroy the seal fast. Polish it with 2000 grit emry cloth.

Worst case is the hiss is under the dash and you end up replacing the MC. Use the tube under the dash too as it could be soemthing other than the MC but I doubt it.

i have to go home and try your instruction

i know as soon as i shut off engine, or step on brake pedal when the engine running, the hissing stop

let's say i describe the free-play distant in term of millimeter
if i lightly tap on the brake pedal, i am talking about very lightly, then slowly push the brake pedal down, the hissing noise (sound wave) changes a little, i am talking brake pedal about maybe 1 or 2 mm down , then at 2 or 3mm, the hissing would just silence

it sounds like as soon as i push the brake pedal enough that the push-rod touches something, it plugs the leak, or stops the hissing.

any DIY to replace the seal?

[fenixus]

hmmm, so it hisses only when you leave brake pedal alone and engine is running?
once you push on brakes (lightly) it stops and then returns immediately once brake pedal returns to loose position, correct?

on the other hand brake booster seem to works fine based on your description.

if you decide to check the o-ring between MC and booster, here is a DIY from 02 solara V6 (1mz-fe), it requires MC removal, no fun later (brake flushing/bleeding sucks):
DIY Master Cylinder replacement (1mz-fe / others similar) *PICS*

I think it might be possible that a gasket/seal behind the booster (where it mates to the firewall) might be leaking a tad and getting sealed once brake pedal arm is pushing on both firewall (towards engine) from the other side and may have nothing to do with the push rod (but check that o-ring too). anyways to remove the booster from firewall, you need to remove the MC first.

but as other posted, unplug booster vacuum lines completely on both ends and block one end and check on the other side if it holds vacuum when using mityvac hand vacuum pump.

Originally Posted by bronzemaxell

i have to go home and try your instruction

i know as soon as i shut off engine, or step on brake pedal when the engine running, the hissing stop

let's say i describe the free-play distant in term of millimeter
if i lightly tap on the brake pedal, i am talking about very lightly, then slowly push the brake pedal down, the hissing noise (sound wave) changes a little, i am talking brake pedal about maybe 1 or 2 mm down , then at 2 or 3mm, the hissing would just silence

it sounds like as soon as i push the brake pedal enough that the push-rod touches something, it plugs the leak, or stops the hissing.

any DIY to replace the seal?

[bronzemaxell]

Originally Posted by fenixus

hmmm, so it hisses only when you leave brake pedal alone and engine is running?
once you push on brakes (lightly) it stops and then returns immediately once brake pedal returns to loose position, correct?

that is exactly what i am trying to describe
thanks for your link