brake booster

[stephanspider2000]

hello
does the hose from the plenum to the brakebooster suppose to have a valve in it?
and which way has the valve have to work?
i have an 2000 fuel injection

[boxdogracing]

I don't believe they is supposed to be a valve (mine does not have one) at least not external. Are the brakes functioning properly? If so I would not worry about it. My understanding is if there is a valve all it would do is hold a vacuum so you could easily push the peddle once or twice with the engine off. On my spider engine off = no power assist.

[BEEK]

the early cars had an inline checkvalve, where the booster had a banjo fitting. the later cars use a 90degree checkvalve at the booster. yes its imperative that there is a check valve.! as long as you are running a booster. i have removed the boosters from some cars for side draft carbs, requires a little more pedal effort, but stops as good as a fiat does, without caliper/rotor modifications.

[stephanspider2000]

well this is why i am asking:
my brakes work well, but when the car is idling i can feel the pedal going down so its losing pressure
I am sure there is no leak (checked that)
when i am braking normal, hard, or an emergency stop it works perfect
maybe the brake booster?
there is no valve in my hose from the booster to the plenum
mine is a 1981 fuel injection

[Ken]

here is a link for troubleshooting brakes, http://www.mpbrakes.com/technical-suppo ... ooting.cfm

[majicwrench]

IF the petal is fading on light pressure it is NOT the booster, it is your master cylinder leaking pressure past the seals.

All the check valve does is retain some vacuum in the booster when engine vacuum disappears, like on accelleration or if engine dies. For the most part, removing valve will not change anything, but it is there for a good reason. It has nothing to do with brake pedal fade.
Keith

[BEEK]

the 90 degree hose adaptor at your booster is the check valve

[mdrburchette]

What Keith says. The m/c is the most likely culprit in this scenario. If you had a booster losing vacuum, your pedal would be hard to push.