Ah, OK. It could be then that your servo and vac pump are in reasonable condition. When a servo is on the way out, it will not hold the vacuum for very long. Your master cylinder is definitely faulty.

 

Without seeing and driving the car, I really do not now want to say replace the servo or not. Personally I would replace it - especially if it were only 52€. (in fact I just sent an email to Autodoc asking them to restock as I'd be interested in one myself to complete the renewal of my brakes😀)

 

Your revs fluctuating is also a good sign as it shows the vacuum pump is working...

Ok good, so i can try to change myself even though i think it taks a couple of hours to make all the process: dismalt old master, bench bleeding the new and bleed all the 4 corners. Right?

Revs fluctuate becuse subtract vacuum to the valve that acuate the egr? 

Yes, easy to change yourself. I am not sure if the cheaper master cylinders come with bleeders. Sometimes they provide four plastic screw bleeders so that you can get air out before you install.

 

NB: A new master cylinder is not going to magically solve all your problems. You have many other issues that need to be addressed. Why not do all the other jobs at the same time and save on the number of times you need to bleed the system?

 

Forget EGR. You are jumping away from the subject again! EGR has nothing to do with brakes! The revs fluctuate because the vacuum pump is working hard to suck air from the servo.

25 minutes ago, Haladams said:

Yes, easy to change yourself. I am not sure if the cheaper master cylinders come with bleeders. Sometimes they provide four plastic screw bleeders so that you can get air out before you install.

 

NB: A new master cylinder is not going to magically solve all your problems. You have many other issues that need to be addressed. Why not do all the other jobs at the same time and save on the number of times you need to bleed the system?

I m thinking of place an order to autodoc of: repair kits for pins and calipers, brake disk, master cylinder, and a new battery as a need it too( i saw autodoc suggest a 56 ha battery but seems low and i have to  check on manuals, any ideas?)

4 hours ago, Zimo said:

I used autodoc already and they are also out of non return valve

Done the test: the first 2 hiss and make the pedal harder , the 3rd dont hiss.(and if i remain on pedal it sink/deflate)  Pretty the same on the previous test.

This morning i had to use the pickup to bring some wood at  a woodworker and standing still at the stop i pumped the pedal for 3 or 4 times and this made the minimum revs fluctuate. Could help?

Yes revs that fluctuate means most likely that the servo Is working. 

It's pulling vaccum and loading the engine. 

Again that continuous loss of pressure still points at a bad master. 

Yes so you @Thefeliciahacker as well as @RicardoM and @Haladams were right(and i never told the  contrary) even though i dont understand why you go straight to that excluding the rest( and yes for sure because i m ignorant but how do you know)

As always many thanks to all

52 minutes ago, Zimo said:

... even though i dont understand why you go straight to that excluding the rest

It's called logic based on experience and it is not a straight process but rather a decision-wise one.

Edited 7 November, 20196 yr by RicardoM

The misunderstanding stems from you having a different process of finding the problem. 

We based on the things you told as pointed out to something precisely. But because the car failed a test of the repair manual you started to belive and approached the issue from a different perspective so no big deal. 

Just tell us what you want to have explained and we will do our best. 

Edited 7 November, 20196 yr by Thefeliciahacker

5 hours ago, Thefeliciahacker said:

The misunderstanding stems from you having a different process of finding the problem. 

We based on the things you told as pointed out to something precisely. But because the car failed a test of the repair manual you started to belive and approached the issue from a different perspective so no big deal. 

Just tell us what you want to have explained and we will do our best. 

As always , my ignorance is speaking, so explain me why coming back home this evening i managed to block front wheels in a emergency braking and i have to do the "ABS system with my foot" .  At the end i still dont understand why i can still brake if(eg.) one the rubber o'ring of my pump is leaking?

Edited 7 November, 20196 yr by Zimo

Because it is a very small leak and your emergency action was quick and sharp so that the part of the o ring without a leak was able to do its job. Only a small amount of fluid manages to escape. If you needed to keep your foot hard on the brake longer before you stopped, then you would feel the leak.

 

 

Zimo, I think it is enough. Change the brake master cylinder. Replace brake fluid. Bleed the brakes. Report how the brakes work.

10 hours ago, Haladams said:

Because it is a very small leak and your emergency action was quick and sharp so that the part of the o ring without a leak was able to do its job. Only a small amount of fluid manages to escape. If you needed to keep your foot hard on the brake longer before you stopped, then you would feel the leak.

 

 

And , i suppose, in the action of braking the oil quantity actually used for brake are a few ml? Many thanks 

On 08/11/2019 at 10:40, Zimo said:

And , i suppose, in the action of braking the oil quantity actually used for brake are a few ml? Many thanks 

It depends on many factors but yes just a few ml. 

 

So in the end a made the shop do the works and (after only 135€ hahah) now it breaks!! Changed the pump and bleeding the lines ....

I hope that in fact it brakes... It would be bad to break 😎

16 minutes ago, RicardoM said:

I hope that in fact it brakes... It would be bad to break 😎

Hahahaja you right! My fault! Yep it brakes! 

Now the problem is the battery that has to be change any ideas?

On 28/11/2019 at 17:20, Zimo said:

Hahahaja you right! My fault! Yep it brakes! 

Now the problem is the battery that has to be change any ideas?

I by the cheapest one available 50amp hour

While serching to replace the master cylinder pump on my non-Abs Felicia i was confused by the diameter that i have found in some brands (as i read in the e-store's description)

 

TRW: 22,2 mm

Brembo: 22,2 mm

......

and ATE: 23,8 mm

 

and i wonder why is that? How the axon from ATE will fit? I something wrong with the list of the e-store?

Accordind to the description that ATE covers the Skoda 6U0 698 019 specification.

 

https://kritosparts.gr/Part/ANTLIA-FRENON-6U0698019/e0036U0698019

 

Can somebody help me?

 

 

6U0698019 is for ABS, 23,71mm.

 

6U0611019 is non-ABS, 22,2mm.

4 hours ago, Papez said:

6U0698019 is for ABS, 23,71mm.

 

6U0611019 is non-ABS, 22,2mm.

 

Thank you, i was confused also by the non-ABS Brembo:

 

M 85035 is 22,2 (ATE brake system) 

https://www.onlinecarparts.co.uk/brembo-1660742.html

 

but M 85042 is also 22,2

https://www.onlinecarparts.co.uk/brembo-1660749.html

is worth to by the 1st over the 2nd?

 

felly comes with girling brakes.
i dont know whats up with the ate stuff

The price is not the same, i wonder what is the difference among them?

Edited 7 May, 20215 yr by D.FYLAKTOS

Hi all, I'm writing up my experiences and symptoms, also the fix regarding this "typical pedal sink".

True, it seems, that there is a "pedal sink" myth... I was sold that at a technical inspection station when i asked the mechanic about it... 

 

So it started by every now and then, when holding the car in traffic from rolling away, that the pedal started to sink...

 

Then it got worse, so I started to google it, read through this thread and decided that I'll replace the master cylinder. 

 

It's done now, with new brake fluid and everything. 

 

Removal:

it was very easy after getting the cables, hoses away (I have LPG)

Syphoned out as much of old muck fluid as I could with a big syringe kept in the garage for such jobs.

Disconnected the union press joints of the brake lines, also no trouble there.

Took off the master cylinder's 2 13mm nuts and pulled it out of the drum. 

Getting the reservoir off the old pump was a bit of a hassle on the bench, but I managed. As an afterthought, if it's nasty dirty, might be better to get a new one... I thought the pump would come with one, but I received the part without. 

Cleaned the reservoir by squirting a bit of brake cleaner into it, shaking and then rinsing it with brake fluid. A google search warned me that  washing with petrol or any solvent might not be a good idea so let's stick to brake cleaner and brake fluid... 

Master cylinder was not bench-bled as I did not get the joints for that. 

Installation:

Was again straightforward, as Haynes says, "reverse of removal" 

Bleeding was done with a vacuum pump

The manual says about the sequence: passenger rear, driver rear, passenger front, driver front. Rear brakes bleed out about 200-300ml, fronts do with 100-200ml. 

I took off about half of that with the vacuum pump, then filled the reservoir and took another half. 

Got very lucky with bleeding now, (low mileage car, lovely to work on) the bleeding nipples were not stuck, and with a bit of fiddling I could use the vacuum pump well. 

 

Brake pedal is hard, pedal travel is short, the whole thing has a much better feel to it. 

 

Thanks for all the info, found on this thread!

Z

30 minutes ago, hzoltaan said:

I took off about half of that with the vacuum pump, then filled the reservoir and took another half. 

 

I prefer the good-old method, two mechanics one pressing the pedal and the other doing the bleeding work.

There is a sieve/filter in the neck of the brake fluid reservoir, was you able to remove this to Syphon out the fluid? Just interest to know if it is removable.