Brakes frustration after VCDS bleed, advice appreciated

It will look something like this picture of a Golf ....

1650983988255.png
 
Mightyleader said:
Thank you @mtl I’ll watch and learn.
@audifan I’ll give it a try bleeding my system then. I have drum brakes on the rear, whereabouts are the bleed valves? I can’t seem to find them.
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I have the same, so you will see the exact location in my video ;).
Anyway, they were slightly rusted on my drums, but a gentle push did the job.
PS: I do not get something: you said that you have already bleeded the brakes. So you should have already bleeded also drums, right?
PS2: I am not a mechanic so do not take this as a 100% correct quide ;) and of course have in mind that my car is LHD car.
 
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philward said:
I pressure bleed every time but not with the engine running. I use an Ezibleed kit.

An A2 collapsible spare is the ideal pressure source.
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Mines a sealey one which just needs hand pumping

Thought engine running might help abs module to opperate but thats wishfull thinking really!
 
Correct brake bleeding sequence according to the manual is
Rear Right
Rear Left
Front Right
Front Left

Although the master cylinder is on the right on RHD cars the ABS unit, which is the distribution point for the brake pipes, is on the left side of the engine bay .
This makes the rear right brake cylinder / caliper the longest route and the front left, the shortest etc. )

Cheers Spike
 
mtl said:
I have the same, so you will see the exact location in my video ;).
Anyway, they were slightly rusted on my drums, but a gentle push did the job.
PS: I do not get something: you said that you have already bleeded the brakes. So you should have already bleeded also drums, right?
PS2: I am not a mechanic so do not take this as a 100% correct quide ;) and of course have in mind that my car is LHD car.
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Good questions, the bleed I did was using VCDS and it only uses the front left and front right bleed points.
 
Mightyleader said:
Good questions, the bleed I did was using VCDS and it only uses the front left and front right bleed points.
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I'm guessing that the assumption is that you have bled the rears already as they are the furthest points, and don't require VCDS. This is my guess from reading this thread, I'd not considered it before, and would probably have done the front, as you did.
Mac.
 
PlasticMac said:
I'm guessing that the assumption is that you have bled the rears already as they are the furthest points, and don't require VCDS. This is my guess from reading this thread, I'd not considered it before, and would probably have done the front, as you did.
Mac.
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Yes I agree, there’s lots of bits of information online but nothing canonical to refer to. Perhaps I need to pull it all together into as post. I’ll add it to my list of things I punish myself for never getting around to….
 
mtl said:
Bleeding valve is down and you need to bow down and also opening/closing the bleeding valve is very uncomfortable due to its position and all other stuff around. Anyway, I could feel my back after this :).

@Mightyleader: here is my process if it is of any help:

@audifan: why do you start on the left rear? Don't you always start with the brake that is furthest away from the brake cylinder? Or do RHD cars have the brake cylinder and ABS pump on the right side?
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@mtl thank you for sharing the video, it’s really good! Informative and clear.
 
You are welcome. I really try to show all the details so that any person can do it. I am glad it helped…
 
Hmmmm OK, I have more information and therefore more questions…

I started the process as outlined in @mtl ‘s video and in the order described for RHD vehicles.
Didn’t get any further than Rear Right… I attached a ring spanner to the valve, and the drain pipe secured in a container.
Pointed the outflow from the valve upwards and, in combination with my partner, went through the process of open valve 1/4 turn > depress brake (no more than 75%) > close valve > release brake > repeat. We did this 10 times and checked the fluid reservoir at the mid-point.
The problem: no fluid came out of the valve and the reservoir did not drop at all :(

My assessment would be that there’s nothing but air in the line OR there’s some crazy blockage somewhere preventing fluid from travelling through the system.
I didn’t go any further to the other wheels yet, just stopped there.

Does anyone have any better analysis?
 
I'd agree with the blockage, but add that in that case, the master cylinder seals must also be letting fluid past. If it was just air, there would be no resistance to cause leakage past the seals, but the reservoir level would be dropping.
 
Mightyleader said:
Hmmmm OK, I have more information and therefore more questions…

I started the process as outlined in @mtl ‘s video and in the order described for RHD vehicles.
Didn’t get any further than Rear Right… I attached a ring spanner to the valve, and the drain pipe secured in a container.
Pointed the outflow from the valve upwards and, in combination with my partner, went through the process of open valve 1/4 turn > depress brake (no more than 75%) > close valve > release brake > repeat. We did this 10 times and checked the fluid reservoir at the mid-point.
The problem: no fluid came out of the valve and the reservoir did not drop at all :(

My assessment would be that there’s nothing but air in the line OR there’s some crazy blockage somewhere preventing fluid from travelling through the system.
I didn’t go any further to the other wheels yet, just stopped there.

Does anyone have any better analysis?
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I would carefully open the valve a further 1/4 turn to see if a flow starts if not increase a further 1/4
& see if any fluid emerges.
 
If fluids coming out then air aint going in so other than making a mess you could completely remove the bleed screw with the pressure bleeding method. Its possible a fault in the abs module could prevent fluid movement but remarkably rare!
 
Howey said:
If fluids coming out then air aint going in so other than making a mess you could completely remove the bleed screw with the pressure bleeding method. Its possible a fault in the abs module could prevent fluid movement but remarkably rare!
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mtl said:
I agree.
Click to expand...

OK, more information and a theory.
I tried doing 1/4 more turn and pumping the brakes on the rear right. Nothing.
Then I tried another 1/4 turn and pumped the brakes. Nothing still.
So I switched to the front right and with pumping got about 20-30mm/1 inch of fluid out, however I could see that with each pump of the brakes it was giving a little more then taking it right back in. It slowly increased the amount but slowly and it never reached the bottle.
Considering this behaviour and all other parts of the system visually appearing OK, I think it’s the master brake cylinder that has blown seals.

1. Do you agree? Master Cylinder?

2. Is this a feasible repair for a person with some reasonable mechanical skills and a pair of axle stands or should I stand back and let the professionals have at it?
 
Mightyleader said:
Morning all,
I'm really frustrated with the brakes on Diane right now, and would love some advice.
Recently, I had the callipers replaced on the front disks as they old ones were causing binding and the pistons were in a sad state.
I had the repair done by a competent local mobile mechanic and I'm more than happy with that work.
Only two issues remained:
  1. The pedal was soft
  2. I still have Brakes/ABS warning lights.
I'll describe the issues I now have from this. After some research on this lovely forum and others in the same VAG vehicle world, it seemed prudent to do a VCDS-driven brake bleed as many had reported it did wonders with soft pedals.
I got a lot of information from this page here on A2OC, which led me to these clear directions (reply #10) on what to expect from the process all of which gave me confidence to go ahead.
So I got bleed tubing with non-return valves as directed, got two 11mm ring spanners and took time to set everything up (up on axle stands, front wheels off etc...) I even thought of a novel way to make the bottles to catch the fluid stand up, see pics...

View attachment 93616 View attachment 93617

Running through the process in VCDS everything seemed to be fine and I saw little air bubbles in the tubing. I topped up the reservoir as the process went on so it never emptied and the bottles collected just under a litre of fluid as the directions said.
HOWEVER. At the end of the process, when VCDS told me the bleed is complete, the brake pedal felt like it had zero pressure behind it and gently pumping it for time made no difference. I put everything back together and did a gentle test moving forward and back on the drive and sure enough there is ZERO brakes applied.
I can only assume that the process caused a leak, pipe split or maybe even the master cylinder seals to go.

QUESTION 1: Is this a correct assumption (I can't see any leaks dropping down under the car) or is there something I have missed and can do to resolve?

Secondly I still have the ABS/Brake warning light so I ran VCDS again and got the following output, which is clearly not related to the hydraulic system. I have checked the cabling to the sensor, the sensor (as best I can, I mean it's there and doesn't look broken) and the fuse.

Code: 
Address 03: ABS Brakes       Labels: None
   Controller: 8Z0 907 379 D
   Component: ESP FRONT MK60      0101
   Coding: 0007175
   Shop #: WSC 00000
   VCID: 49E5B47460A1
2 Faults Found:
00668 -  Supply Voltage Terminal 30
            002 -  Lower Limit Exceeded - Intermittent
00285 -  ABS Wheel Speed Sensor; Front Right (G45)
            012 -  Electrical Fault in Circuit

QUESTION 2: Are there any common places to check for issues in the wiring?
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Hello, I expect you are all bled out with brake bleeding tips, I remember reading once in Haynes manual aiming at issues if the master cylinder was drained or low to use a power bleeding technique where either the front two or rear two were simultaneously opened while bleeding. I tried it once when my power bleeding tube came off and drained my master cylinder that worked for me.
 
Ref this post by Fishman, test the master cylinder before replacing it.

Weird Brake Problem!!

I can't answer that wasn't there to see it. How did you bleed the brakes and how did the garage. If pressure bleeding must NEVER EXCEED 1 BAR pressure. What has the garage said to you? It is possible that a faulty unit has been fitted. You have to be a bit more careful with the A2. As said I...
www.a2oc.net
I think the cylinder ports which supply the ABS unit are M12 x 1 and bleed nipples are readily available in this size on ebay . With the 2 ports blocked off, the pedal should be 'solid' If not, then the master cyl seals are suspect.
I'd also remove each bleed nipple, one at a time, and check the drillings are clear, Spare standard size bleed nipples or temporary plugs would be useful to minimise brake fluid loss

I went through a similar issue on another Audi, Convinced myself it was the master cylinder and replaced it - and it made no difference.

Cheers Spike
 
OK I have a solution!
Turns out the rear cylinders have small leaks both sides which isn;t huge surprise since they not been replaced in my ownership.
Going to look into replacing those as well as the shoes. Probably fiddly so may get someone to do it.
Still got the warning on the ABS wiring but will try to trace that myself too.

Thanks everyone for the help.
 
OK, I replaced the Cylinder shoes and associated springs etc… with a Febi Bilstein kit on both rear wheels. Not too bad though the handbrake cable was a b*tch to reattach. Bled the rears too.

So now I’m back where I started. Working brakes, slightly soft pedal and still got that damned ABS error warning.
I’ll rerun VCDS to see if it can clear now if it’s magically changed. Otherwise I am in for long and I suspect frustrating hunt for a wiring fault between the front right sensor and the ABS controller.
I got the wiring diagram but it doesn’t help me much, been way too long since I could parse that sort of thing so an input on the error (posted way out top of this too long thread) is welcome!
 
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