Correct brake bleed sequence

[FrenchAudi]

In reality it doesn't matter - but you're supposed to bleed furthest away from the reservoir first and work your way forward. That way you don’t introduce old fluid into the freshly bled lines.
I used 1.5ltr bleeding my old B8 - but that was overkill. 250ml each line should do it.

If you empty and dispose of the old fluid in the reservoir, then bleed 1 litre, you then need about 250 ml or so to fill the reservoir

[b206]

If you empty and dispose of the old fluid in the reservoir, then bleed 1 litre, you then need about 250 ml or so to fill the reservoir

250ml per line which is 1ltr plus a top up. Lets be honest, if you take it to Audi or an indie, they will shove 1ltr through the system (that’s what the manual says). Only the caliper plus a small section of line goes through a heat cycle anyway. Yes it's hygroscopic, but they don’t give a damn! As long as the majority is flushed is their rule

[arman123]

Them instructions came from the Audi repair manual using the vas bleeding kit

[FrenchAudi]

250ml per line which is 1ltr plus a top up. Lets be honest, if you take it to Audi or an indie, they will shove 1ltr through the system (that’s what the manual says). Only the caliper plus a small section of line goes through a heat cycle anyway. Yes it's hygroscopic, but they don’t give a damn! As long as the majority is flushed is their rule

I consider the fact that brake fluid is hygroscopic to be the major reason for changing it, and that high temperatures have less harmful effect.

Brake fluid absorbs more and more water at the air interface in the reservoir, until it becomes saturated, after which the moisture begins to separate, and gradually descends to the lowest part of the system, which is inside the brake cylinders. This, together with the fact that moisture also enters there via the piston seals, is why corrosion always occurs in the cylinders.

Absorbed moisture also reduces the boiling point of the fluid drastically, which was proved to me on a couple of occasions when I managed to boil the fluid in the front brakes, which is why I now prefer to change it every two years.

[johnvw]

Hi to All,
many thanks for th replies.
l just can not believe what a Pandora's box I have opened. After many hours of Google searching, visiting various Forum sites (US, Brit and AUS ), ringing a service centre, call not returned and a major PDF file from a mechanical engineer with years of brake experience, I have come to the conclusion that there is no specific sequence or the secret is firmly held under threat of death.
There would appear to be two different systems of braking, diagonal and front / rear, with various versions of each now in existence. I found it very difficult to obtain specific Quattro information.
Brake fluid bleed sequences found : L left, R right, f front, r rear.
Lr Rr Lf Rf
Rr Lr Rf Lf
Lr Lf Rr Rf
Lr Rr Lf Rf
Lf Rf Lr Rr
Oh dear !!
For my RHD the brake master cylinder is on the left side of the engine bay, looking from the front of the car. So I thought start furthest from the master cylinder and finish at the Rf ( drivers front wheel ).
Closer inspection revealed two 8/10 mm supply lines going to the ESP on the right side of the engine bay with four lines exiting, I assumed the configuration was a diagonal system ( would be nice to have this verified ).
Not being any the wiser I bleed Rr Lr Rf Lf ( passengers front wheel ). All appeared to go well, no sponginess, no fault lights and most importantly, no swear words.
Removing the old fluid from the reservoir took an eternity. I could not see the max level and bleed very cautiously as not to empty the container and cause trouble for the ABS.
If there exists a diagram of the braking system All will be revealed.
The last word,
More experience to tackle other maintenance, greater confidence, more care taken, financial gain and broader knowledge base.

Now to repeat the operation for my wife's 2011 mark 6 Gti, wish me luck.
Regards
John

[Rob69]

I'd say as long as the system has not been broken into at the reservoir / master cylinder / ABS end of things then the actual bleeding sequence is not so important. If there has been air introduced high in the system then it is maybe more critical and the ABS pump needs cycling as well. I think the old sequence of diagonal bleeding goes back to the early days of dual circuit brakes when the master cylinder first got two sets of pistons and seals, one for each circuit. I had an old 1967 type 2 van years ago with single circuit brakes, not good when a brake line split on the MOT rollers!

[FrenchAudi]

Hi to All,

Removing the old fluid from the reservoir took an eternity. I could not see the max level and bleed very cautiously as not to empty the container and cause trouble for the ABS.

John

It would be much easier to syphon it out with a bit of plastic tubing.

If only someone would tell me how to remove the little filter in the top of the reservoir without destroying it!

Incidentally, it is wise to replace the fluid at the recommended intervals, before so much moisture is absorbed that it separates and collects in the cylinders.

If this happens, the water will be in the bottom, while the bleed nipples are at the top, and will be unlikely to be removed just by bleeding