Brake servo problem

[samellio]

I've noticed that when i left foot brake (can't do it to save my life but having fun trying ), after the first pump of the pedal there is no power assistance and its just like having no brakes.. However as soon as you come off the gas the brake pedal returns to normal :?
Basically- gas and brakes=no brakes- the pedal goes hard and is like it would be if the engine wasn't runnung..
Anyone got any ideas???
Cheers
Sam

 

[sypher]

the servo is vacum assisted so at idle you have a neg' pressure in the manafold and servo assistance but when you are driving and have boost the servo iss NOT assisting the master so it feels like the engine is off

 

[Fast Guy]

There should be a one way valve in the line to the servo, to stop the boost getting to it. So basically your servo will have no vacuum to make it work if you left foot brake.

 

[sypher]

yup sorry there is a check valve that is there to maintain the suspended vacum action of the servo, won't even try to explain this over posts maybe somebody else will.. just remember that the servo needs vacum to work and it gets this vac from the engine, so when ur driving and holding the engine above vacum you get once MAYBE two pumps of the pedal before it goes hard

try pump pedal with engine off (hard) then start engine try pedal(easy assistance) let idle then turn off, now try pedal(soft,soft,hard) now hold brake pedal down and start engine, pedal should drop now has assistance

if you allready now this SORRY don't mean to be patronising

 

[samellio]

Thanks chaps,
I think i understand what your saying...
Just think how f**t we'd be if the throttle jammed open and it stuck in gear :?