Hissing Brake Cylinder/ Brake Booster

[noobmechanic]

Hi
I have seen other posts about Brake Boosters that have started leaking and need replacement.
I have been following this post http://www.solaraguy.com/viewtopic.php?f=1&t=50281, as I have the same symptoms.
My CEL is on and there is definite hissing (that I can feel with my finger) between the Brake Master Cylinder and the Brake Booster.
I have replaced the 'paper' gasket between the too with no change.
There is rust on both sides so I want to make sure I replace the right part.
Pics attached.

Id appreciate any feedback.

[dinoxor]

go to your local auto store and pull the code for free
do a quick search on that code to see if there are any solutions here

[noobmechanic]

Thanks for the response, but I have the code, P0171, a lean fuel condition... (in my case due to vacuum leak) which has been narrowed down to the 2 parts in my pictures.
Again, I have the same symptoms as the post I have been following to troubleshoot (in my original post).
There is loud air noise in the cabin on the drivers side whenever the breaks are pressed. I have done the brake booster test for airtightness and it has failed, but since the 2 parts work together to create the vacuum, I want to make sure I replace the correct piece and hopefully not both parts.
The problem is definitely cause by moisture getting in between the 2 and causing rust. Im trying to find out if both parts are busted as a result or not.
Plus.. I can feel the leak with my finger when the car is running, which is why I replaced the gasket between the parts, which was the direct fix of other posters with this problem, but it didnt fix my leak so its definitely one of the parts.

[sliDingSolAra...]

is the hissing coming from the MC??? can you hear it inside the car? did you check the vacuum lines and check to make sure the booster itself hasnt separated in any way?

[noobmechanic]

the hissing is coming from the connection where the MC and booster bolt together, so i dont know if the MC or the booster is the faulty part which is why I posted the pictures.
yes I can hear it inside the car, louder when the break is pressed.
the vacuum lines are good and i can feel the exact spot where the leak is, i can touch it with my finger.
i have done the booster 'test' and the break pedal never tightens up when pressing multiple times with the car off, so there is no air-tightness.(the seal on the booster looks to be intact to me (see picture) so it could be the MC breaking the seal, possibly because of the rust, but im unsure)

im trying not to take the booster apart if i dont have to which is why i posted the pic of the MC. That is the part of the MC that presses up against the booster to form the seal, so i was hoping someone could determine if the rust ate enough away to break the seal, i really dont know how to test the air-tightness of the parts individually (ie. not bolted to each other).

[sliDingSolAra...]

the hissing is coming from the connection where the MC and booster bolt together, so i dont know if the MC or the booster is the faulty part which is why I posted the pictures.
yes I can hear it inside the car, louder when the break is pressed.
the vacuum lines are good and i can feel the exact spot where the leak is, i can touch it with my finger.
i have done the booster 'test' and the break pedal never tightens up when pressing multiple times with the car off, so there is no air-tightness.(the seal on the booster looks to be intact to me (see picture) so it could be the MC breaking the seal, possibly because of the rust, but im unsure)

im trying not to take the booster apart if i dont have to which is why i posted the pic of the MC. That is the part of the MC that presses up against the booster to form the seal, so i was hoping someone could determine if the rust ate enough away to break the seal, i really dont know how to test the air-tightness of the parts individually (ie. not bolted to each other).

well i hate to say it but if it was the MC, you'd see brake fluid. the MC can't hiss because there's not suppose to be air in the lines, and if there was air in the brake lines you would have spongy pedal. the booster is the only part of the brake system with air. tomorrow i'll post how you can test the booster yourself, im about to PTFO,

[sliDingSolAra...]

the hissing is coming from the connection where the MC and booster bolt together, so i dont know if the MC or the booster is the faulty part which is why I posted the pictures.
\.

ok so here's how you test your brake booster. BTW i go to school for Auto Tech and im getting my associates degree in the spring, i saying this just so you know that i'm not pulling this info outta my ass lol

Steps to Check Booster:
- Pump brake with ENGINE OFF
-- Foot on pedal and START ENGINE
--- After engine starts with foot on pedal, PEDAL SHOULD DROP 1-2inches
IF THIS HAPPENS YOUR BRAKE BOOSTER IS FUNCTIONING PROPERLY

0000000000000000000000000000000000000000000000000000000000000000000000


Steps to check the Check Valve
- ENGINE OFF, wait 10 MINUTES do not touch brake pedal after turning engine off or while waiting
-- after 10 min press pedal. should give 1 or 2 stops (or in other words 1 or 2 pumps of pedal)
--- IF pedal is hard and waiting, check valve if defective


im almost certain it can't be your MC simply because if you had a leak you would see brake fluid and your brakes would not function properly.

HOPE THIS HELPS!!!

[noobmechanic]

Ok, thanks for the info.
The booster failed the test, and when i removed it, i could press the plunger with my hand and hear the air come out the other side.
I replaced it and so far so good, the leak i could feel under the hood is gone, breaks are working fine, and I removed the CEL, so Im just waiting to see if it stays off now.
Fingers crossed.

Thanks for the help!

[sliDingSolAra...]

Glade to hear it worked out for you!!