With the engine not running and the vacuum bled away with a couple of pumps of the pedal I have a rock solid pedal and I can stand on it with great force and it will not sink at all no matter how long I maintain the force.

 

If I then start the engine as the vacuum builds up the pedal sinks a little as it should once the servo assistance cuts in but if I maintain the pressure then the pedal will gradually sink to a point not on the floor but just above where it becomes spongy but will not go down any further, its about 75% of the reserve travel that it sinks.

 

If it sank to the floor and also did it with the engine running I would know its the master cylinder seals but this has me confused, is it a characteristic of the ABS system perhaps?

 

Its not noticeable when driving because you are never braking that long before coming to a stop, I do not notice it if I am holding the car on the brakes at a junction so think it needs more than the pressure required just to hold the vehicle steady, perhaps more pressure than normal braking.

 

Its the same sort of feeling you get in a full blown ABS stop without the modulating, the pedal sinks in the same way but slower.

 

Any ideas? Does yours do this as well?

 

I replaced the fluid today and bled through the whole system but wont start the car to test the brakes till tomorrow as I am monitoring the battery drain.

18 minutes ago, J.R. said:

Does yours do this as well

 

Yes.  2007 2.0tdi 4x4.   I discovered this during one of the RoSPA training sessions when I was told to put my foot on the brake and my finger pulling the steering whel when I started the car; this to check the relevant servos were working OK.

All the way slowly virtually to the floor or just the pedal initially sinking a little further with the servo assistance?

Almost all the way to the floor, but slowly.

I have similar experiences but only with the Octavia, I've heard it's a VAG thing.

 

I would suggest checking the tandem pump vacuum and the wobbly nipple connection, then the rigid plastic hose to the servo.

 

If all checks good, try purging the ABS with diagnostic tool.

An update after a more detailed consideration of brake pedal behaviour this morning;

- engine off,

- clutch depressed,

- foot firmly on brake  pedal,

- finger pulling on steering wheel. 

- Start engine,

- steering wheel moves as servo kicks in,

- brake pedal _slowly_ depresses under firm pressure until about 2/3 the way down then goes no further.

 

A selection of rolling brake checks at various speeds and conditions failed to disclose any anomalous behaviour - brakes were absolutely fine.

 

A feature, maybe?  Perhaps we need more Octy 2 drivers to carry out the same checks and report?

 

...Its a funny issue in that, yes this does happen and it is normal but also, this can happen if the system is leaking or has air/water, in the system!

 

I think air/water route will be more noticeable, and you will find the brakes not operating properly are they overheat and fade with hard driving but your issue won't, if it is normal! Doh! It's like a non-problematic problem!

 

I would suggest, if you think the issue is NEW, go get the system checked, if it has always been there, its most likely ok but do also remember, most manufacturers recommend replacement of brake/clutch fluid every two years so you will almost certainly have to have that done, in order to eliminate a possible fault. You might pay for this to be dome and find no difference though but at least you will have peace of mind, if the garage sy all is good! (I can't believe they would say this without changing the fluid, first).

FYI the steering is electrically operated and not hydraulic.

MRGF. I can easily prove/disprove that hypothesis, give me a minute................................

 

Just tested after flushing and bleeding the entire system yesterday, no difference, pedal still falls to just short of the floor with engine running.

 

On the road with several 70mph - 15mph full on ABS emergency stops the pedal remains firmer and the ABS lasts a few brake tests longer before wheels will no longer lock up so the new fluid has made an important safety contribution that I hope will never be needed.

 

I did a very light downhill braking over a very long distance and did not notice the pedal going down like it does under the stationary test conditions so dont think this "characteristic" manifests itself on the road, it might with cooked brakes and an overloaded trailer going down a mountain.

 

 

I had similar symptoms before and I put it down to air in the ABS system. My Dad had changed a rear caliper and ended up letting all the fluid leak out. He bled the system multiple times, used VCDS to run the ABS pump and the pedal was never the same again.

 

The pedal was solid with the engine off and it always passed the MOT so it ended up with a mediocre brake pedal for about a year or 2 before I had a  go at bleeding the system and managed to noticeably improve it by bleeding all the brakes and running the ABS bleeding procedure on VCDS many, many times.

 

I'm not saying this is your issue but don't underestimate how much of a ball ache it can be if earlier on in your cars life there has been some work done and there is some air left in the system somewhere and requires the ABS pump to be run a fair bit to flush it out.

I have been thinking along those lines, whilst I know that I have not let any air into the system, used hose clamps etc the pedal just does not feel right, the initial bite is not there (could be pad material) and the modulation is not right.

 

After another test this evening I definitely have a caliper piston drag on the one I've been faffing around with, not enough to stop turning the wheel by hand but its 100° hotter than all the others after a short drive, like the possible air in the ABS pump I think it may always have been like that.

 

Once the rear calipers are changed and perhaps some decent pads I will try the ABS bleed procedure, I'm told it uses loads and loads of fluid especially if you have to do it many times like you, is that the case?

 

Are you still bleeding individual calipers while actioning the ABS pump via VCDS, is that how it works?

 

I have been using a vacuum bleeder (Chinese Mytyvac) and whilst it works well it draws in air around the bleed nipple threads so I will have to get an adaptor for my old Easybleed for when I do the ABS bleeding as I want to see if air comes out and when it stops.

 

Any suggestions for brake pad material that has a decent initial bite? not for track days or anything just something that will give me more confidence than the budget pads that came from Autodoc.

 

Editted, I think you are right about the ballache from a previous garage, they had fitted the piston seal reversed so could well have let the fluid drain out. My neighbours Octavia which is a couple of years newer has a really good pedal feel and bite.

Edited 24 May, 20197 yr by J.R.

It doesn't use that much brake fluid but I guess that depends on your definition of a lot. I'm pretty sure the 5L of brake fluid I bought was less than £20 and I didn't make that much of a dent in it really.

 

Using the VCDS method it will ask you to depress the pedal and the ABS pump will then kick in and pressurise the system, it then gives you instructions as to which bleed nipples it wants you to open and it will ask you to pump the brakes maybe 10x and then close the nipples and it will go through and cycle the pump again, you basically just follow the steps and click done which takes you to the next step.

 

 

Very late on this topic, I know, but I have exactly the same symptoms as the OP reported. It bothered me at first as I'd not had that experience on any other car, but I've had the Octy 1.9PD 2008 (1Z5) for 10 years and 105,000m and it's always been the same. It's also never failed an MoT on the brakes, and passed its last one 3 days ago.

I've never fully changed the brake fluid on the Octy, nor on any car I've owned, including an Octy 1.9 2000 (1U). I had the latter for 12 years and it never had any issues with the brakes. Does make me wonder whether changing the fluid every two years is simply a stealer tactic.

I get that brake fluid is hygroscopic but, it is retained in an airtight system. I would have assumed that if the fluid was contaminated, I'd have suffered some form of problem by now.

Anyhow, I'm assuming this is simply an Octy/VAG peculiarity and is nothing to worry about.

@beezera10 The cars braking system might well have to be air tight to operate, but it is not perfectly 'airtight' which is why H20 can then be in the system and the brake fluid. Seals deteriorate, as do brake pipes.

Millions might not change brake fluid and never be aware of brake fluid overheating or the water and brake fluid.

But then millions might never use brakes hard, or get discs or pads very hot.

Many might leave engine oil and filters untouched for years. Each to their own.

Our car just does normal journeys, never in a position to get really hot as far as the brakes are concerned.

As for oil, quite the opposite when it comes to maintenance. 10-12k/annual with new filter every time (507 longlife oil too).

In my opinion, it's quite impressive that a car can do 105,000m over 10 years without having a fluid change and never have a brake issue.

?

What is impressive?

So you never had brake failure.

Many people never carry out preventative maintenance and never have issues, maybe never will and maybe eventually they will.

Maybe

I would do the ABS Bleed Procedure. I have done that on ny Yeti and you only need access to both front brake bleed nipples.

This resulted in a much firmer engine running brake pedal than before the ABS Bleed Procedure.

So both front wheels on axel stands with wheels removed.

It is an easy procedure but you need a few litres of brake fluid in a pressure bleeder.

The rear wheels can be bleed normally after the ABS Bleed procedure is completed.