# Reservoir cap should be air tight right? brake bleedding...



## zguy (Sep 13, 2001)

I'm having a heck of a time getting my brakes and clutch bleed. SOmething that sees percular is the reservoir cap hisses when I step on the brake pedal. I put soap around the collar, and its leaking air where the sensor goes through the top of the cap.
This should be air tight and not leak correct?


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## zguy (Sep 13, 2001)

*Re: Reservoir cap should be air tight right? brake bleedding... (zguy)*

This is on a B3 Passat with the two piece cap.
The outer collar, and the inner "post" where the two sensors connect through.


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## Vdubs (May 16, 2001)

*Re: Reservoir cap should be air tight right? brake bleedding... (zguy)*

No they have a breather hole, it is not a sealed system. 
If there wasn't a breather the level wouldn't be able to go down as the brakes wear and more importantly fluid wouldn't be able to return to the reservoir as the brakes get hot which will make the brakes bind.


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## spitpilot (Feb 14, 2000)

*Re: Reservoir cap should be air tight right? brake bleedding... (Vdubs)*


_Quote, originally posted by *Vdubs* »_No they have a breather hole, it is not a sealed system. 
If there wasn't a breather the level wouldn't be able to go down as the brakes wear and more importantly fluid wouldn't be able to return to the reservoir as the brakes get hot which will make the brakes bind.


Absolutely correct...all brake systems must vent to the air...which is why the brake fluid sucks up moisture from the air and must be flushed every two years to avoid corrosion in system and brake fade caused by the moisture lowering the boiling point of the fluid! http://****************.com/smile/emthup.gif


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