ABS system flush

I want specific information about the process, so that I'm prepared when the time comes. I have a Motive pressure bleeder and VCDS. Already searched as much as I can, but still am a little confused.

1. Does the car have to be on a lift or jackstands with no wheels touching the ground? Why?

2. Is 29 psi really necessary? Seems high... don't want to damage any seals

3. Do both front wheel bleeder valves need to be opened when flushing the ABS? How about the rears wheels? I want to have tubing and bottles ready

4. What is the purpose of running the output test?

5. Does flushing the ABS use a lot of new fluid? I have 2 litres for brakes + clutch + ABS, don't want to run out halfway through

I'll take a crack, neimis.
1. I don't think so; just makes it easier to get to the bleed screws at each wheel.

2. 2bar (29psi) "required to bleed the ABS Hydraulic Unit -N55-"; for a simple system flush, I don't think you'd need 29psi, but rather, just enough to push the new stuff through

3. As far as I'm aware, the only time you need to bleed the ABS is when it gets air - like when changing a caliper, or running the master cylinder dry.
In which case, yes, the ABS bleed procedure does ask you to open both FR and FL bleed screws and then pump the brake pedal 10x.

4. Got a screen shot showing what you're asking about?

5. From what I recall, a full flush is 1.15L, including clutch; if you're doing the whole ABS thing and pumping the brakes 10x multiple times...maybe have double that.
(Why are you doing ABS flush? Regular maintenance says to simply do the "out with the old, in with the new" flush.)

Oh - found it.

Thanks for the reply, Nuje, especially the fluid capacity chart.
My car is due (overdue, actually) for a brake and clutch fluid change.
I have read so much conflicting advice and methods, it's hard to keep it straight.

1. Regarding the wheels being off the ground, I read something about checking the rotation of all 4 wheels as the VCDS is going through the procedure?? requiring a second person helping and turning the wheels

2. I've read brake bleed procedures using a simple gravity bleed (oilhammer), to 15 psi, to Ross Tech's 29 psi.

3. oilhammer: "I know they say you shouldn't have to bleed the ABS, but experience has shown me otherwise. Actually, you'd be surprised how improved the pedal feel gets on cars that haven't even had any brake work done if you run the Output Test. I think the ABS module needs to be exercised once in a while."

4. I don't know what the output test does or how it works, I haven't gotten that far yet

5. Some people report that you need to go through the ABS bleed procedure 17 times, which I assume would end up using a lot of fluid.

Totally confused at this point. Might end up skipping the ABS flush and just do the brake and clutch.

As far as I'm aware, to do a flush, you don't need VCDS. The "maintenance" procedure from erWin simply states that you pressure up your pressure bleeder, then proceed to bleed each of the four wheels, plus the clutch.

I've asked the techs at VW (and with my wife's Audi), and all they do on the scheduled / mandated "2yr. brake fluid change" is pressure bleed everything. Oilhammer obviously has a lot more experience than I do, but VW documentation doesn't mention it.

Having been through that bleed procedure a number of times trying to fix the soft pedal in my Mk4, I get the feeling it'll go infinitely; it "stops" when your battery drops below the minimum voltage needed to keep VCDS happy.

I changed the brake fluid on my wife's 2015 TDI a couple weeks ago.

I used a Motive Products Pressure Bleeder filled with 2L of fluid.

I only used between 6 and 8 PSI of pressure. I'd pump it up to 8 and then pump it more when it went down to 6.

I didn't jack the car up at all. I just bled one caliper at a time with a tube connected to run the fluid into an old milk jug.

For the first caliper I allowed it to bleed for a long time, to use up what was in the reservoir and the lines. I probably put 500ml through the first one.

For the rest I bled about 200ml through each one, for a total of 1100ml, give or take.

Transmission is automatic so there's no clutch. Can't comment on that. (I'd guess it's the same as my old Mk4 Golf, but I'm not sure having never seen under the hood of a manual Mk7).

As long as you never let the reservoir go too low, you don't have to use VCDS to purge air form the ABS pump.

Hi Mike, thanks for your reply.
I'm OK on the standard brake and clutch fluid flush part - pretty normal, not too different from past years (except "LV" fluid and revised flush order).

It's all the unsaid things in an ABS flush (eg. "wheels off the ground?", "bleed hoses attached to 2? 4? calipers", "pump brakes with bleed valves open? closed?" "repeat procedure 2? 6? 17? times" "battery charger necessary?" etc. that I'm confused about. I don't want to start the procedure and then find out I don't have the tools or supplies to finish the job.

I've done the ABS flush on my Mk4 a couple times, both times was because I had replaced a caliper, which let air into the system.

On that car I didn't jack it up or anything. I just connected hoses to both front bleed nipples, opened them as instructed by VCDS, held the pedal when it said to, and then closed the nipples and pumped the brakes 10 times when instructed. I repeated this many times because I had lots of fluid in the pressure bleeder. Just guessing 20 times? Probably way more than necessary.

At the step where it says to pump the brakes 10 times I believe it says something like "Pump brakes 10 times valves closed" which I took to mean they should be closed while doing it. I closed them at that step and re-opened them at the step where it says to hold the pedal down while it activates the ABS pump.

After that, I proceeded to bleed a little more out of each caliper to ensure there was no air. Brakes worked fine after that.

Edit: I didn't use a battery charger.

Hi guys. Jack here I have a question on the brake bleeding procedure on my 2002 TDI new beetle. I have been trying for around a year to bleed the brakes without the VCDS Software, I have tried pumping and vacuum bleeders no luck. I gave in and purchased the VCDS as I would like to adjust the injection timing as well. Now that I have it I still can't find the brake bleeding section you guys are talking about I ran across it when I first set up the software but I can not find it now. Thanks in advance.

(First of all, just FYI, you posted in the Mk7 forum - I know it's easy to miss that when you hit a thread from a search).

But anyway, from what I remember:

1. Plug in, turn on ignition (don't start car)
2. Launch VCDS
3. Choose module 03 - ABS
4. Choose "BASIC SETTINGS"

That should get you the ABS pump bleed procedure. My experience is that it'll go as long as you have proper voltage coming out of the battery (translation: you will go through a LOT of brake fluid if you just keep following the "PRESS/HOLD - OPEN FL/FR BLEED SCREWS - PUMP PEDAL 10x - CLOSE BLEED SCREWS - PRESS/HOLD" etc. cycle)

2-3 rounds of that should suffice.

IIRC, you can then also choose OUTPUT TESTS and that'll guide you through running the ABS pump for each wheel.

Thank you so much! "Don't start the car" that could explain it, I had it running. Now I'll have to go apoligize to her, I cussed her out (in German so she could understand, lol) One last thing, I would like to check the start of injection timing as well and I'm not familiar with what Mk or what section I should look in on here, could you point me in the right direction? Thanks again!

Don't want to derail this Mk7 ABS thread, so for injection timing, try:
check adjust injection timing vcds site:tdiclub.com

Type that into Mr. Google (or whatever search engine) and you should get something useful.