Hi guys, please can someone put my mind at rest?

I've recently replaced front brake discs and pads then I changed the brake fluid using an eezibleed.

With the engine off, the brake pedal is as hard as rock when it's been pumped a few times. When the engine is running if I pump the brake pedal it goes really hard (as I expected) but then slowly slowly sinks a couple of inches if I keep pressing hard.

I suspected a problem with the master cylinder but the interweb is telling me this is 'normal' for some tdi's, and something to do with the vacuum.

Other websites say it's a problem.

Any ideas?

This is normal. And long as the pedal feels good when driving all is OK. My car is exactly the same after a brake fluid change but brakes work perfect.

I believe it to be normal. I had a 2L petrol that used to do the same. It always had a soft pedal that pressed hard enough with the engine running you could almost get it to the floor but there was never any detriment to braking performance. Equally you could pump it up to high and hard pedal with the engine off as you deplete the vacuum in the servo.

Thanks for the replies so far, is this specific to the octavia then? I have tried a Peugeot 206 and the pedal pumps up to rock hard and can't be pushed down at all with the engine both off and running.

I have always been led to believe if the pedal slowly sinks then it needs bleeding of air or a problem with the seals somewhere, probably in the master cylinder. If you type 'brake pedal sinking' on google lots of car forums are saying it's not normal, but on an octavia it is?

Can anyone explain why it happens?

Thanks

That symptom can be as a result of a worn master cylinder allowing fluid to leak past the piston although it would ultimately bottom out. Air in the system gives you a spongey pedal that can be pumped up and the pedal does sink afterwards. I asked my garage when I discovered this and they said it was normal, I also had it picked up as an advisory on one of my MOTs but as it wouldn't bottom the pedal and the brake weight tests had been as expected they passed it. If you are in any doubt or feel that the car isn't going to stop get it checked as, I believe, a proper bleed of the system involves activating the ABS pumps

Hi guys, please can someone put my mind at rest?

I've recently replaced front brake discs and pads then I changed the brake fluid using an eezibleed.

With the engine off, the brake pedal is as hard as rock when it's been pumped a few times. When the engine is running if I pump the brake pedal it goes really hard (as I expected) but then slowly slowly sinks a couple of inches if I keep pressing hard.

I suspected a problem with the master cylinder but the interweb is telling me this is 'normal' for some tdi's, and something to do with the vacuum.

Other websites say it's a problem.

Any ideas?

 

 

Did you solve this problem?

My brakes behave the same. When engine is off, pedal is hard. With engine running, brake pedal sinks down when depressed but no spongy feel or lack of performance. In fact brakes work very well, just sinks to the floor. MOT is due in January, will see than .

When u bleed the brakes should the car not running?

+1

Pedal creep.

Try a new model at the dealer and compare.

All cars with ABS are rubbish. OEM callipers are rubbish - especially on old rusted cars. People don't break hard enough to correct rusty parts - I've seen many cars with rusted rear disc.

 

Before you start the car - pump the pedal..you force brake pads to correct distance from discs.

 

I would try bleeding/replacing brake fluid.

 

I would guess it has got something to do with ABS. No matter how hard brakes you have, ABS wrecks anything.

 

My last UK car has got some ABS sensor fault or so - if I pushed car hard on standard brakes (only EBC green stuff pads), hit the pot hole...wheel started to bump off the road...ABS screaming and eventually switched off brakes completely. Great system :-D