help 2.0 astra brakes

[astrasi123]

i have 2.0 astra front disks and calipers on my corsa. i have bleed the break system but they are still spongy . the brake pedal is hard when the engine isnt running . but if i leave my foot on the pedal and start the car the pedal moves down about 1cm and becomes spongey when driving .. what could this be . as i need to get it sorted as nearly had a accident tonight were car didnt stop

[scotty cav turbo]

When you pump the pedal with engine off, your removing all the air out of the servo (which is correct) When you start the car with your foot on the pedal it will travel as the servo is now working. (which is correct) Firstly, pump the pedal untill it goes hard and then does the pedal sink to the floor with the engine off?

[astrasi123]

na its stays hard.... but when the engine is running it goes spongey like theres air in the system

[scotty cav turbo]

Try bleeding again then. Clamp off the flexie hoses one by one and pump the pedal to see if it makes a difference. Bleed the brake which makes the pedal feel better.

[astrasi123]

i bleed the hole system replaced all the old oil and hasnt made no diffrence i wouldnt have to change the bios on the servo would i. as i read some were on here people have had to change it

[scotty cav turbo]

Changed the old oil There is no bias on a servo. All as servo does is reduce muscular effort, ie make it easier to push the pedal down. Well if the pedal goes hard and does not sink to the floor when the engine is not running, then the master cylinder seems to be holding pressure which is good. If you've bled them prop then theres nothing else i can see whats going to cause spongey pedal. Are they new discs and pads??

[astrasi123]

yep new disks and pads. when the car is running i can push the pedal right down to the floor so its touching it

[scotty cav turbo]

Only thing to suggest is clamp off the flexie pipes and go round induvidually pumping the pedal with the engine running and see if one makes the pedal feels any better. All the back brakes fine and adjusted up ok?

[astrasi123]

yep

[Chrex]

hmm...this sounds like ther is a leak somewhere.

have you checked the callipers and rear cylinders for fluid seepage?

Has the car got ABS? is unusual for you to have pedal to floor movement with new fluid and fully bled system.

double check the whole system for leaks or cracks...

[astrasi123]

there is no leaks . and na the car hasnt got abs .