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2000 forester s
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7 Posts
Discussion Starter · #1 ·
I was out today and noticed that there was a hiss at lower speeds that stopped when the brakes were applied. I looked under the dash and confirmed that it was coming from the brake input shaft. I realize that this is a vacuum related item, and understand its workings, but i was curious to see if anyone else had run into this before. Possible that the booster is on its way out?
It is extremely cold here today and this is the first time i've noticed it, but this is my girlfriends car, so I dont drive it much. My guess is that the seal is cold and there is nothing else wrong, but I just wanted those in the know to give me their opinion.
The car is a 2000 Forester S, approx 127xxx on the odo.
Thanks for your insight!!
 

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04 Forester XT MT
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269 Posts
In my experience with non subarus. if your loosing vacuum through there you need a new booster
 

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Registered
2000 forester s
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7 Posts
Discussion Starter · #3 ·
That is part of the problem, I'm not loosing brake assist pressure at all!! The brakes are still acting as they had all along, but now with a hiss when my foot is OFF the pedal. When I go down into the footwell and and move the boot around the brake input rod I can change/eliminate the hiss for a little but it returns when I next depress the pedal.
 

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Registered
2000 2 Outbacks 1Man , 1 Auto
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312 Posts
Could be the check valve which forms part of the vacuum hose going between the servo and the manifold. Basically a one way valve stopping vacuum from decaying in the servo. They can get noisy even though brake function might be ok. Worth replacing at that mileage.
 

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Road Warrior
2005 Outback Wagon 2.5i
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409 Posts
If it's coming out the brake pedal shaft it is in fact the booster loosing vacuum pressure. The booster needs to be replaced.
 

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Ol' Timer
2006 WRX Spec-C 6MT
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5,961 Posts
Back from the dead. My Outback is doing the same thing, only when really cold and there is no change in pedal action.
So, what happened? I thought it would be the booster, but why only when it's cold? And it's only happening about twice a week, only on start up during really cold mornings.
 

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Premium Member
2004 Forester 4EAT
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5,462 Posts
Small leak that is only apparent when rubber is hardened from being so cold? It will get worse in time.
 

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15 Posts
check for vacuum leaks ... particularly at the vacuum ball and the "three way splitter" ... look for dry-rotted rubber at all connections ... see if you can hear where the hiss is coming from ... check all vacuum fittings ...
 
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