1.9tdi Brake Pedal

[aubrey]

I'm getting conflicting answers. I bled my brakes recently and run the master dry. My big mistake.

 

But I then rebled and did VCDS ABS bleed. I now have this common issue when brake is rock hard at top with the engine off, but start the engine and the pedal goes down a bit but if I push it just a little harder goes further down and then stops a bit higher than a fully depressed clutch.

 

Anyone know if that is full travel or does full travel actually hit the floor ? As I say the brake pedal stops a good inch above a fully depressed clutch pedal.

 

I read loads on the web about this is air but I've bled and bled and activated ABS via VCDS and no air comes out.

 

I then blamed the master cylinder but on fitting a new one it is the same.

 

The brakes work great with normal driving, grab really hard at the top of the pedal. It is just this extra sinking I now find odd. Maybe I getting paranoid and it always did this, hence my question to others to try their car.

 

Then I read stuff that this is normal on Diesel TDIs http://forums.motester.co.uk/view_topic.php?id=441&forum_id=4&highlight=VW+brake+pedal

 

In fact I should add I even took it to a VW specialist at the weekend for a full brake bleed who told me that my brakes were fine and this behaviour is normal, they run it round their carpark and they said no need to waste your money getting us to bleed the brakes as it will be exactly the same afterwards.

 

So my question to my fellow 1.9TDI owners. Does your car do this ? Just get in the car with the engine off, push down on your brake pedal, firm at the top, then start the engine. Does your pedal sink right down ?

Edited 25 September, 2017 by aubrey

[RichardatWakefield]

Hi Aubrey,

Haven't tried doing that, but I believe that is normal, because sans-engine there will be no servo-assistance, such as when being towed, brakes still work, but being all-discs, you have to press much harder than with engine on.

 

Once you start up, the vacuum pump starts to evacuate the big servo vacuum reservoir tank, whose function is to help you push the brake pedal, and the growing vacuum pulls the pedal down, giving you that pedal-sinking feeling.

HTH.

Richard

[stratosg]

Mine works as yours @aubrey and it does this since new. By the way I will test it tomorrow morning and I will let you know. Just to be sure we are Ok.  Pleas keep in mind mine is 1.2Tsi 77Kw

Edited 25 September, 2017 by stratosg

[KenONeill]

@aubrey - I won't repeat the earlier stuff, but this is entirely normal for any vacuum servo car, if you pump the brake pedal engine off so that you drain the servo of energy.

[stratosg]

@aubrey. Hi again. I checked again my break pedal. 

 

As the engine was off, I pressed the pedal till it got solid rock. 

 

Then I started the car and felt my pedal going down to floor. When stopped I pressed it as hard as I could. Pedal stopped a little higher than clutch pedal.  To be honest it felt like there was a stopper under my pedal. 

 

So as KenONeill wrote. Everything normal.

[Robjon]

^^^ Exactly how I remember it was in my (much missed) Roomy Scout.

[aubrey]

Well thanks everybody. I think that settles it then. That is how it's meant to be.

One final thing I should add is doing the ABS output test where VCDS asks you to repeatedly hold and release the brake pedal does make a big difference. You hold the pedal and the ABS runs and shakes your foot about. At the end of the process when VCDS said 'Done' my pedal is much firmer. I think I underestimated on my description of just how soft my pedal felt, it really would sink too easily whereas post the ABS output test it's back to normal.