brake pedal going to the floor

[msg]

The car is a 2006 diesal rodeo.Done 45000km. Today the brake pedal started to go all the way to the floor if held on for 7 to 10 seconds. The resivor is full of fluid and no signs of a leak.
With the engine off you can pump the pedal back up and hold it and it stays at the top, then holding the pedal on start the engine and the pedal drops about 10mm befor creeping down to the floor again.
Is this a problem with the master cylinder or could it be something else that I am missing.


thanks Matt

[wardy1]

does it only happen if you steer a certain way? IE to the left or right?

[msg]

Does it all the time,consistantly the same ,even just sitting in the driveway at home

[jezzaGQ]

it could be your brake booster i had a similar problem after doin my master cylinder (which was leaking) turned out my booster had shat itself aswell just a thought

[msg]

If the booster was shagged wouldnt you just get a really hard pedal with no feel and not a pedal that goes to the floor, since there is no brake fluid in the booster so it cant leak internally or externally and allow the peddl to go to the floor

[jezzaGQ]

if its really hard it would be a vaccum problem had that happen too on a diesel most vaccum set up is on the altinater which is for ur brakes but petrol not sure how that works

[KiwiBacon]

Honestly a lot of vehicles have a brake pedal that will fade to the floor if the pressure is kept on it for long enough.
Compare your vehicle to a lot of others and see how it feels. Especially with the engine off to take out the vacuum assist effect.

If your pedal is worse than everything else, you might have a seal or bore problem in your brake master cylinder.

[mkpatrol]

Master cylinder is shagged. Common syptom.

Take it back to Holden, it shouldnt be shagged after that short a time & yes if you bosster is stuffed it can give a hard pedal amongst other things.

[mkpatrol]

Master cylinder is shagged. Common syptom.

Take it back to Holden, it shouldnt be shagged after that short a time & yes if you bosster is stuffed it can give a hard pedal amongst other things.

[nerida67]

if its the master cylinder ?? it would go to the floor wether the motor is running or not
generally if theres air in the line u can "pump"up the pedal, then it slowly goes bak to the floor
it could be the booster , split diafram
or pull the pipe from the booster and check the valve in the line

[mkpatrol]

Not neccecarily, the foot pressure on it's own might not be enough to the the master cylinder to bypass.

Boosters either make a noise or stop giving assist. They cannot cause the pedal to alter as the travel is guided by the hydaulic part of the brake system (master cylinder).

I bet if the op dropped off the pressure inthe pedal & waited a bit longer then the pedal will sink with the engine off.

Air in the lines will make the pedal spongy, not sink.

[clever80]

Does the car have ABS, as it happened overnight it could be a sensor giving a false reading.

[msg]

Take it back to Holden, it shouldnt be shagged after that short a time & yes if you bosster is stuffed it can give a hard pedal amongst other things.

But it is out of warranty..... Does that count????

[msg]

Does the car have ABS, as it happened overnight it could be a sensor giving a false reading.

There is no ABS..... No sensor reading - Foot reading

[thunder]

same thing with my GU ute with 45000 on the clock.. master cylinder