Another Brake-bleeding thread!

[Tarmageddon]

Hi there,

I've put the subject as "Another Brake-bleeding thread" because I searched the topic and can see it's been discussed before, but there seems to be a lot of different answers and I'd really like some clarification and help!!

First, the car:
Model: Audi S4
Type: B5 Avant
Year: 2001
ESP: Yes
Brakes: Standard rear, Porsche 993TT "Big Red" calipers up front.

Back-story: I took the car around Castle Combe a couple of months after I bought it and cooked the brake fluid completely, presumably because it hadn't been done in a while. Got it home and went to change the brake fluid, found the bleed nipples on the front calipers were shot. Tried to fix them, failed, bought new calipers.

Work so far: I've completely drained the brake fluid using a venturi type vacuum bleeder as I didn't want any remnants of the destroyed brake fluid mingling with my nice, new and very expensive Castrol SRF racing fluid. I then filled the reservoir with some cheap standard dot-4 and used the vacuum bleeder to drag it through to all four corners to flush the system, then completely drained it again. The only exception was the clutch, I managed to strip the brake fluid from the brake system but the reservoir level was still slightly above the clutch pick-up line so I left it, the clutch was (and still is) working fine and I don't want to bleed that at this stage. I'm working on a driveway and although I haven't made a concerted effort yet I'll find it VERY difficult to get all four wheels (or even two) off the ground at once because the car is so low, at the moment I'm working on one corner at a time (yes, I'm bored of removing and re-fitting road wheels)

Current situation: I used a pressure bleeder at just over 20 psi and bled the brakes at all four corners, ignition and engine were off. I found mixed opinions about the order to bleed them in so I did Passenger Rear, Drivers Rear, Passenger Front (inner then outer) and lastly Drivers Front (inner then outer) ... at each nipple I got firstly air as expected, followed by bubbly brake fluid, then the bubbles cleared and I got good, smooth, clear fluid out of all six nipples.
At the test drive however it was obvious that there is still a huge airlock somewhere in the system, the pedal is solid when the engine is off but when the engine is running it'll go almost to the floor. Driving it is scary to say the least, it WILL stop, but there is zero "feel" to the pedal.

Now, I've looked on this forum and found a lot of similar posts, and also had various "experts" giving me advice on Facebook too, but a lot of the information is conflicting. Here's a summary of what people are saying:

• I've done it lots of times and never had a problem (this seems to be mainly people who don't drain the fluid past the ABS pump)
• You don't need the ignition on
• You need to bleed with the ignition on
• You need to bleed with the engine on
• You need to bleed in the "correct" order, furthest from reservoir to closest
• You need to bleed in the "wrong" order, closest to the reservoir to the furthest
• You don't need VAG-COM
• You DO need VAG-COM
• When using VAG-COM you open the Passenger Front nipple and fire the pump
• When using VAG-COM you have to flash it once with each nipple open

So based on that lot what I'm really wondering is what on earth I do next... I have ordered Ross-Tech VCDS (VAG-COM) anyway as I think it's going to come in useful in the future, but when it arrives and I go back to bleed the brakes again what IS the procedure? So far as I can gather I pressure-bleed the system again, probably from closest to furthest this time, and quite possibly with the engine running, and then plug in VAG-COM, open the Passenger Front nipple and flash the ABS pump... but what then, do I keep flashing it until I see the air that WAS in the ABS pump come through the nipple? Or do I flash it once and then use the pressure bleeder to push the bubble through? Has anyone actually had this problem on this model of car before and successfully fixed it without paying the Audi garage £235 for the privilege, and if so how?

Sorry it's such a long post for what is a fairly simple question, but I think part of the problem on the threads I've seen so far is a lack of information to start with, hopefully that's not the case this time!!

Thanks in advance!

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[Kenrevo]

I having a similar problem, I've bleed the brakes multiple time but still seam a little soft. I have Vag-com and have bleed the abs system, first front left and then all of them. It gotten better but I still have air some place. I think there is air in the master cylinder. My next step is to bench bleed the master cylinder when I have free time.

[MacFady]

I'm leaning towards Kenrevo. I've bled plenty of brakes before without issue but I've never completely drained fluid from the reserviour during the process, that's what I try to avoid, acknowledging that you were trying to completely replace what was there.

[armageddon-]

It could be air traped on abs pump, try to loose conections on pump to let air out.

[Tarmageddon]

I thought that's what the VAG-COM cycling does? Forces air out of the ABS pump?

There also seems to be a difference of opinion if you have to have the pressure bleed still attached when you cycle the pump, does the pump force the air out of its own volition or just open valves to allow the pressure through?

Also, your username makes me feel slightly awkward

[armageddon-]

Yes, vag-com does that, but some times is not enough and is easier if the air do not have to travel all brake line.

[Tarmageddon]

Ah ok, so basically it's possible to manually bleed the ABS pump!

Would like to avoid it if possible, and I find it odd that we have to resort to all these measures, makes me wonder what magic and wizardry is in the VAG 1869... I guarantee the Audi garage would have it done straight away, but they want £235 for the pleasure!

[Tarmageddon]

Right, problem solved!! I'll explain how I sorted mine in case it's useful to anyone else in future.

I got Ross-Tech VCDS through yesterday and used it today.

The instructions on the Ross-Tech website say that the car has to be 4 wheels in the air to start with, but unfortunately my S4 is so low that this really isn't an option so I put the Passenger side front up on the jack. I figured there was no real reason to have the wheels in the air, it's not as if the ABS pump was going to try to spin them!

I connected up a pressure bleeding kit with about 12-15psi and cracked open the inner bleed nipple.

With the ignition ON I went to the ABS control module (03) in VCDS, selected "General settings (04)" and was given the screen to run various scenarios, on my car group 2 was to bleed the system.

This is where it got slightly weird, on the Ross-Tech website it says to select the group and click "Go" whereas on my car simply selecting the group cycled the ABS pump and the Go button was greyed out, so you had to click "Down" and "Up" between groups 1 and 2 to activate the bleed. I don't think this is right, as it would make much more sense to pre-select the group and press Go, but either way it worked.

I didn't know whether the ABS cycle was going to actually pump the liquid through, or just open valves for the pressure bleed to push it through.

After the first couple of runs I noticed that the ABS pump pushed fluid through a lot more quickly than the pressure bleeder, and I was also worried that depending on where the ABS pump was in the system the pressure bleeder might actually be pushing against it, so I disconnected the bleeder.

I got very few bubbles out of the passenger front caliper, and although the pedal felt improved it still wasn't great, so I decided to do all four.

I connected the hose to the passenger rear and got a friend to cycle the ABS pump, this time we got a LOT of bubbles out, and must have cycled the ABS pump 20 or 30 times, each time with lots of really big bubbles before we got three consecutive cycles with no air.

Repeated the process for drivers side rear and this time cycled the pump 10 times (I wanted to make sure I didn't have a bubble travelling down the line and left in there) with no air at all.

Drivers side front got a few small bubbles and then three consecutive cycles with no air.

Put the car back down, road test, brakes are back to normal. They're not GREAT at the moment because the previous owner installed some cheap pads which I cooked a bit but the main thing is there's no air in the system.

So, in summary for anyone else trying this:

• Bleed the brakes with a pressure bleeder first, ELSA says PR, DR, PF, DF
• Ignition ON
• Connect Ross-Tech VCRS (VAG-COM)
• Disconnect pressure bleeder
• Select Control Module 03 (ABS) and select General Settings (04)
• Put catch pipe etc on first bleed nipple and open it
• Select appropiate group which says Bleed System (On mine it was group 2)
• Keep cycling the pump until all the air is out, I used 3 consecutive cycles with no air bubbles as an indication
• Repeat for all four corners
• Remember to keep topping up the reservoir as you can get quite a bit of fluid pushed through by the ABS pump.

As a side note when I first drove the car the ABS and ESP lights were on, and the red brake warning started beeping and flashing. I braked pretty hard and the ABS and brake warning switched off. I went home to reset the ESP light using VCDS but when I turned the ignition back on after I had got the laptop all set up it had gone off by itself.

Hopefully this little guide is useful to someone, I must say VCDS is the best £270 I've ever spent, not only did I save £230 for the Audi garage doing it for me, but it's there for all future occasions AND has all the other vast number of functions you get with VCDS AND I can charge other VAG owners £10 a time for a code-read, saving them a fortune on having it done at a dealer... I expect it to pay for itself in no time.

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[vavJETTAw36]

Glad you got it bled all the way. I am really surprised you were able to do this with the front jacked up. I've read somewhere, I think ecs, that it is almost impossible to bleed the system if the car is not close to level.


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[Tarmageddon]

It wasn't jacked up by much, just enough to get each wheel off the floor in turn. Also it's pretty stiff so it was tilted more side-to-side than it was fore and aft. I'd love to have done this with all four wheels in the air but I don't have a ramp and it's tricky trying to get it on 4 axle stands.

[MacDaddy]

I think all the confusion comes from esp vs non esp cars, but since I'm not for certain I'll leave it at that so I don't dilute the thread.

Great info though, the spongey brake pedal is an issue that has plagued many b5 owners (a4/s4/Passat) and it's nice to finally have a definitive answer.