Audi Allroad brakes - pulling, no feel, faulty circuit

[allan_audi]

Hi,

Can anyone help re: Audi Allroad brakes.

Problems started a while ago when right hand front caliper seized (pistons were stuck) and brakes started to lose feel.

I fitted new caliper, and overhauled the rest. Bled the brakes over an over again, even used VAGCOM to run the pump, but still it had the lack of feel and pulled to the left.

Finally today got round to fitting new master cylinder, bled again and again with VAGCOM, pressure bleeder, even directly on the pedal, but I couldn't belive the brakes were exactly the same.

While it was up on ramps, I wedged the brake pedal, to the point where the brake lights come on. I was confused, I could move the front right and rear left (same circuit), but the other two, front left and rear right were biting. Apply further pressure and you could start to feel the other circuit starting to work, but the others would be locked. The circuit does eventually lock too, but not at the same time.

I know all the calipers are free, even the slide pins.

It seems the original caliper seizing may have been a symptom of something else failing.

Anyone have any ideas? Please help! I need to be sorted, as it seems to be getting worse.

[Columbo]

Is it an Auto or manual?

If it's manual you need to bleed the clutch cylinder first, then the brakes.

Bleeding sequence
1 - Front right brake caliper
2 - Front left brake caliper
3 - Rear right brake caliper
4 - Rear left brake caliper

Aparently there are two typres of ESP unit 5.3 and 5.7.

5.3 needs a pressure of at least 2 bar is required for bleeding the ESP hydraulic unit. Therefore always check the pressure setting on the bleeding device.
First, all of the brake calipers are bled using the conventional method.
Afterwards the ESP hydraulic pump needs to be bled. This is done using vagcom
Vagcom is used to actuate the hydraulic pump for 10 s.

Unlike ESP 5.3, ESP 5.7 does not incorporate hydraulic pump -V156. Therefore it is not necessary to bleed the system with the diagnostic tester.

Taken from service manual. Hope this helps.

[allan_audi]

Thanks, but I've used the correct bleeding sequence from ElsaWin, I always use the tyre to pressurise the system, so about 34PSI, which I think is more than enough. I suppose I could be losing pressure during the bleeding. I've run the ESP pump up too. I've tried te complete procedure several times but with no difference.

The trouble is I would expect if the problem was air then the brakes would "pump up", to the point where they're working properly but they don't.

Anybody have any other ideas?

[lonky]

Auto bleed kits always say to lower the pressure to 1 bar - 15psi in the tyre.

This is done so as not to damage the storage tank, and when it presurises it can blow air through the fluid which totally defeats the object of the exercise.

[NickPicks]

Auto bleed kits always say to lower the pressure to 1 bar - 15psi in the tyre.

I'm pretty sure Elsawin states that aswell.

[allan_audi]

Elsawin quotes "at least 2 Bar" so around 28PSI, a few more PSI is not going to harm.

Anything less than that and the fluid hardly moves, especially the rear calipers.