Vectra (54 plate) brakes with ABS

[pingu748]

Am i right in thinking a brake system is airtight ? If so is it right that when sitting at lights / stationary I can put my foot on the pedal an it will go to the floor ... not immediately but over about 3 seconds ... if i then do the same again it is much firmer ,,, and if I then drive and brake within about 30 seconds its dead sharp & responsive ... is this normal ? ... brakes seem to stop me ok but am thinking they could be better ...

[Paul22118]

An hydraulic braking system is not airtight as it requires a vent to the atmosphere, usually via a pin hole in the top of the car on the brake fluid reservoir.
This is one of the problems because brake fluid is hygroscopic, that is it will absorb moisture from the atmosphere and over time effectively have its water content raised. This in turn means that when the brakes get serious punishment the water content makes the fluid change to a gas (steam if u like) and then becomes compressable. This is not desireable.

That said what you have described is not correct. No brake pedal under these circumstances should go to the floor even after a while of holding the pedal firmly down.

STOP DRIVING and take the car to a garage. It is likely you have either a leak in the system allowing fluid to escape or within the system which means it is sloshing around inside but unable to hold the pressure required, which is considerable.

[woodchopper]

I remember noticing this happening on several of my previous cars - never found anything wrong with them and they worked perfect.
Someone told me it was to do with the vacuum in the inlet manifold as the servo assistance works off this.
Dont know wether it was true or not but never had a problem with them not working.
Let us know if you find out?

[__LEE__]

If your vectra is a diesel , then it is quite normal for the brake pedal to sink about three quarters of its normal travel..


Woodchopper.. If you drove your previous cars in the condition where the pedal reaches the FLOOR , then you was clearly a danger to other road users.. If trying to convince others that it is normal to do so then mabe the motoring section is not for you..

[markja]

if your pedal goes to the floor stop driving.
get the car recovered to a garage (don't drive it there! )
this is very,very, v,v,v,v, dangerous.
there is a leak in the master cylinder and it will fail soon. at the moment sharp braking makes the seal in it wedge against the sides of the cylinder, so it seems to work o.k.
the next time you use the brakes could be the time that the seal fails completly and you have NO BRAKES AT ALL!!


note to anyone being 'rear ended ' by a Vectra on a '54 plate, check if it's pingu who hit you!!

[BillyNoMates]

As has been said - definately something wrong there.

No braking system should allow the brake pedal to reach the floor, engine on or off.

I do a static brake check before driving off each morning - before starting the engine - I expect to find some resistance there.